Intussusception
Intussusception is the telescoping of a proximal segment of bowel into an adjacent distal segment, causing intestinal obstruction and potentially compromising mesenteric blood supply.
Intussusception
Intussusception derives from the Latin intus ("within") + suscipere ("to take up") — literally, a segment of bowel being "taken up within" itself. Invagination of a portion of intestine into an adjacent portion [1].
More precisely, the proximal segment (called the intussusceptum) telescopes into the distal segment (called the intussuscipiens). The mesentery of the intussusceptum is dragged along with it, leading to venous congestion, oedema, ischaemia, and — if untreated — necrosis and perforation [2][3].
It is the most common abdominal emergency in early childhood and the most common cause of intestinal obstruction in infants between 6–36 months of age [2].
2. Epidemiology
- Peak incidence: 4 to 24 months [1]. The majority of patients are younger than 2 years [2].
- Uncommon before 3 months and after 6 years of age. When it occurs outside this window, a pathological lead point should be strongly suspected [2][3].
- In adults, intussusception is rare and almost always secondary to a structural lesion (polyp, lipoma, GIST, carcinoma) [5].
- In Hong Kong, intussusception remains a common paediatric surgical emergency. The typical patient is a well-nourished infant aged 6–12 months presenting in autumn/winter (coinciding with peak viral gastroenteritis season). Awareness of this condition among parents and primary care physicians allows earlier presentation and higher rates of successful non-operative reduction.
- Rotavirus vaccine (Rotarix®, RotaTeq®) is part of the HK childhood immunisation schedule. There is a small but recognised increased risk of intussusception in the first 1–2 weeks following the first dose of rotavirus vaccine, though the absolute risk is very low (~1–6 per 100,000 vaccinated infants) [4].
3. Anatomy and Relevant Function
Understanding why intussusception occurs most often at the ileocaecal junction requires appreciating the anatomy:
- Terminal ileum: The last ~20–30 cm of the ileum is particularly rich in lymphoid tissue (Peyer's patches) — aggregated lymphoid follicles in the submucosal layer. These are part of gut-associated lymphoid tissue (GALT) and are most prominent in childhood, gradually atrophying with age.
- Ileocaecal valve (ICV): A physiological sphincter at the junction of the ileum and caecum. It acts as a one-way valve. The abrupt change in calibre (narrow ileum → wide caecum) and the lip-like valve structure create a natural "funnel" into which the ileum can prolapse.
- Mesentery: The ileal mesentery is relatively mobile and long in children, allowing the ileum to prolapse into the caecum and ascending colon.
The combination of:
- Abundant lymphoid tissue (prone to reactive hyperplasia → acts as a "lead point")
- Calibre change at the ICV (creates a natural telescoping point)
- Mesenteric mobility in young children
...explains why ~85–90% of paediatric intussusceptions are ileocolic (ileocaecal) [4].
| Site | Description | Notes |
|---|---|---|
| Ileocolic | Ileum telescopes through ICV into colon | Most common (85–90%) in children [4] |
| Ileo-ileal | Small bowel telescopes into itself | More common post-operatively; more likely to resolve spontaneously; less likely to respond to pneumatic reduction [2] |
| Jejuno-jejunal | Jejunum into jejunum | Rare; usually pathological lead point |
| Colo-colic | Colon into colon | More common in adults; suspect malignancy |
When the intussusceptum is dragged into the intussuscipiens:
- Mesentery is compressed between the two layers of bowel → venous obstruction first (veins are thin-walled and compress before arteries)
- Venous congestion → oedema of bowel wall → bloody mucus secretion ("red currant jelly stool")
- If untreated, progressive oedema → arterial compromise → ischaemia → necrosis → perforation → peritonitis
- Luminal obstruction → proximal bowel dilatation, vomiting (initially non-bilious if the obstruction is distal; bilious if proximal to ampulla of Vater or as condition progresses)
4. Etiology
- May be preceded by viral infection [1].
- 75% of cases are idiopathic — no clear pathological lead point is found [2].
- Proposed mechanism: Viral infections (URTI, gastroenteritis — particularly adenovirus, rotavirus, enterovirus) cause reactive lymphoid hyperplasia of Peyer's patches in the terminal ileum [2][3].
- Enlarged Peyer's patches (90%) act as a "lead point" — the hypertrophied lymphoid tissue protrudes into the lumen and is caught by normal peristalsis, which propels it distally, dragging the proximal bowel with it [4].
- This explains the seasonal variation (autumn/winter peaks coinciding with viral season) and the age predilection (Peyer's patches are most prominent in infancy/early childhood).
Why Idiopathic Intussusception is a Disease of Infancy
Peyer's patches are most prominent at 6–24 months of age. They are the infant's primary immune sampling tissue in the gut, highly reactive to new antigenic exposure. After ~2 years, the lymphoid tissue starts to involute. This is why intussusception peaks at this age and is rare in older children or adults without a lead point.
A pathological lead point is a structural lesion within the bowel wall or lumen that acts as the "anchor" dragged by peristalsis. It is more common in children > 3 years and in adults. In adults, intussusception is ALWAYS associated with pathological lead-points (usually intraluminal lesions in SB), e.g., polyp, submucosal lipoma, Meckel's diverticulum, GIST, carcinoma [5].
| Lead Point | Notes |
|---|---|
| Meckel's diverticulum | Most common pathological lead point in children. A true diverticulum containing all bowel wall layers. Should be considered in recurrent small bowel intussusception [6] |
| Polyps | Juvenile polyps, Peutz-Jeghers polyps (hamartomatous), adenomatous polyps |
| Lymphoma | Small bowel lymphoma (Burkitt lymphoma in children); always consider in older children with intussusception [4] |
| Duplication cysts | Congenital enteric duplication cysts act as mass lesion |
| Henoch-Schönlein purpura (HSP) | IgA vasculitis → submucosal haemorrhage/oedema in bowel wall acts as lead point [2] |
| Submucosal lipoma | More common in adults |
| GIST / Carcinoma | Adults — always rule out malignancy |
| Appendiceal stump | Post-appendicectomy; the inflamed stump can act as lead point |
When to Suspect a Pathological Lead Point
Always suspect a pathological lead point when:
- Age < 3 months or > 6 years
- Recurrent intussusception (especially small bowel)
- Ileo-ileal location (not ileocolic)
- Adult presentation — assume malignancy until proven otherwise
- Occurs after abdominal or retroperitoneal surgery (1–21 days post-op).
- Caused by uncoordinated peristaltic activity during recovery or traction from suture lines/feeding tubes [2].
- Usually ileo-ileal (not ileocolic), making it difficult to diagnose and not amenable to pneumatic/hydrostatic reduction.
- Diagnosis requires a high index of suspicion in any child with post-operative abdominal distension and vomiting.
- Rotavirus vaccine (particularly the earlier RotaShield® vaccine, now withdrawn) was associated with intussusception.
- Current vaccines (RotaTeq®, Rotarix®) carry a very small increased risk (~1–6 extra cases per 100,000 vaccinated infants), predominantly within 1 week of the first dose [4].
- The benefit of vaccination (preventing severe rotavirus gastroenteritis) far outweighs this small risk, and vaccination remains recommended.
5. Pathophysiology
The sequence of events in intussusception follows a logical, step-wise progression:
-
Why venous obstruction before arterial?
- Veins are thin-walled, low-pressure vessels. When the mesentery is compressed between the intussusceptum and intussuscipiens, veins are occluded first while arterial inflow continues → venous engorgement and haemorrhagic oedema of the bowel wall.
-
Why "red currant jelly" stool?
- Venous congestion → transudation of blood and mucus into the bowel lumen. The mixture of blood and mucus gives the characteristic dark red, jelly-like appearance (like redcurrant jam). This is a late sign and indicates significant mucosal ischaemia — it means the condition has been present for hours [4].
-
Why colicky (intermittent) pain?
- Each peristaltic wave attempts to propel the intussusceptum further into the intussuscipiens → intense visceral pain during the peristaltic contraction → relief between contractions.
- As the condition progresses, the pain may become constant (suggesting ischaemia/peritonitis).
-
Why bilious vomiting?
- Bilious vomiting occurs because the obstruction is distal to the ampulla of Vater (in ileocolic intussusception, the obstruction is at the ileocaecal junction) → bile-stained vomiting indicates intestinal obstruction [4].
- Initially vomiting may be non-bilious (reflex vomiting from visceral stimulation), but as obstruction progresses, it becomes bilious.
-
Why a "sausage-shaped" mass?
-
"Dance's sign" (emptiness in RIF)
- As the caecum is drawn up with the advancing intussusceptum, the right iliac fossa becomes empty to palpation (the caecum has been "pulled up"). This is called Dance's sign.
Intussusception causes mechanical small bowel obstruction. The general pathophysiology of intestinal obstruction applies [4]:
- Proximal dilatation: Initially, increased peristalsis attempts to overcome the obstruction. Soon, gas accumulates (swallowed air + bacterial fermentation) and fluid accumulates (failed absorption + secretion from oedematous wall).
- Dehydration and electrolyte imbalance from:
- Reduced oral intake
- Vomiting
- Defective intestinal absorption (oedematous bowel wall)
- Transudation of fluid into the peritoneal cavity (third-spacing)
- Strangulation: Unlike simple obstruction, intussusception causes strangulated obstruction (mesenteric compromise) → ischaemia → necrosis → perforation → faecal peritonitis and sepsis.
6. Classification
| Type | Description | Frequency |
|---|---|---|
| Ileocolic (ileocaecal) | Ileum prolapses through ICV into colon | 85% in children [4] |
| Ileo-ileal | Small bowel into small bowel | More common post-op; also HSP, Meckel's |
| Jejuno-jejunal | Jejunum into jejunum | Rare |
| Colo-colic | Colon into colon | More common in adults (think malignancy) |
| Type | Description |
|---|---|
| Idiopathic | No structural lead point; reactive lymphoid hyperplasia (~75–90% in children) |
| Secondary (lead-point) | Structural lesion acts as lead point (Meckel's, polyp, lymphoma, etc.) |
| Post-operative | Uncoordinated peristalsis after abdominal surgery; usually ileo-ileal |
| Vaccine-associated | Following rotavirus vaccination (rare, first dose) |
| Type | Description |
|---|---|
| Reducible | Can be reduced by pneumatic/hydrostatic enema or manual surgical reduction |
| Irreducible | Failed non-operative reduction; requires surgical intervention |
| Gangrenous | Bowel necrosis has occurred; requires resection |
7. Clinical Features
The clinical presentation of intussusception is one of the most classic and exam-tested presentations in paediatric surgery. However, the classical triad (intermittent colicky abdominal pain + red currant jelly stool + sausage-shaped mass) is present in fewer than 50% of cases [4].
| Symptom | Description | Pathophysiological Basis |
|---|---|---|
| Intermittent colicky abdominal pain | Sudden onset, severe, episodic (every 10–20 min), child draws up knees and screams; pain-free intervals between episodes | Each peristaltic wave propels the intussusceptum deeper → intense visceral stretch and ischaemia → pain; pain resolves when peristalsis relaxes |
| Inconsolable crying | Especially in younger infants who cannot verbalise pain | Visceral pain from mesenteric traction and bowel wall ischaemia |
| Bilious vomiting | Initially non-bilious (reflex), becoming bilious as obstruction progresses | Obstruction distal to ampulla of Vater → bile cannot pass distally → refluxes proximally. Also increased proximal intraluminal pressure → reverse peristalsis |
| Red currant jelly stool | Dark red, mucoid bloody stool; this is a LATE sign | Venous engorgement of the trapped bowel → transudation of blood and mucus into the lumen. Indicates significant mucosal compromise. Not present early — by the time it appears, there is already significant ischaemia [4] |
| Lethargy / altered consciousness | May mimic sepsis or encephalitis; drowsiness between episodes is characteristic | Thought to be due to endorphin release in response to severe visceral pain, or possibly from endotoxin absorption from ischaemic bowel. This can be a red herring — a lethargic infant may be misdiagnosed with meningitis/encephalopathy |
| Refusal to feed | Child stops eating | Nausea and abdominal discomfort; intestinal obstruction causes anorexia |
| Fever | Low-grade initially; high-grade suggests complication | Mucosal disruption → bacterial translocation; late fever suggests necrosis/perforation/peritonitis [4] |
| Abdominal distension | Progressive as obstruction develops | Proximal bowel dilatation from gas and fluid accumulation due to mechanical obstruction |
The Lethargic Infant — Don't Forget Intussusception!
A common exam pitfall: an infant presenting primarily with lethargy and pallor may be misdiagnosed as sepsis, meningitis, or even non-accidental injury. Always consider intussusception in a lethargic child aged 6–24 months, especially if there are intermittent episodes of distress. A simple abdominal ultrasound can save a life.
| Sign | Description | Pathophysiological Basis |
|---|---|---|
| Sausage-shaped mass in RUQ | Palpable, firm, slightly curved mass, usually in the right upper quadrant or along the transverse colon | The telescoped bowel forms an elongated mass as the intussusceptum advances along the colon [4] |
| Dance's sign | Emptiness or "hollowness" on palpation of the right iliac fossa | The caecum has been dragged superiorly with the intussusceptum → the RIF is empty |
| Blood and mucus on PR examination | "Red currant jelly" may be detected on rectal examination | Venous congestion → haemorrhagic transudation. PR examination may reveal blood before it is passed per rectum |
| Rarely: prolapsing mass through rectum | In advanced cases, the intussusceptum may be visible at the anus | Extreme advancement of the intussusceptum through the colon; must be differentiated from rectal prolapse |
| Signs of dehydration | Dry mucous membranes, sunken fontanelle, tachycardia, reduced urine output | Vomiting + third-space fluid losses + reduced intake |
| Signs of peritonitis (late) | Abdominal rigidity, guarding, rebound tenderness, absent bowel sounds, high fever, tachycardia, hypotension | Bowel necrosis → perforation → faecal peritonitis. This is a surgical emergency |
| Abdominal distension | Generalised distension | Mechanical bowel obstruction → proximal bowel dilatation with gas and fluid |
Classical Triad vs Reality
The classical triad of intussusception is:
- Intermittent colicky abdominal pain
- Red currant jelly stool
- Sausage-shaped abdominal mass
However, this full triad is present in fewer than 50% of cases. The most reliable and earliest feature is episodic, severe colicky pain with pain-free intervals in an infant aged 6–24 months. Do not wait for the full triad before investigating — early ultrasound is key.
Understanding the chronological evolution helps you assess severity:
| Time Frame | Features | Implication |
|---|---|---|
| Early (0–6 hours) | Intermittent colicky pain, vomiting (non-bilious), irritability, drawing up of legs | Bowel telescoping with intermittent peristaltic episodes; no significant ischaemia yet |
| Intermediate (6–12 hours) | Pain becoming more frequent, bilious vomiting, lethargy between episodes, palpable mass | Progressive obstruction; venous congestion developing |
| Late (12–24+ hours) | Red currant jelly stool, fever, abdominal distension, signs of dehydration | Significant venous congestion → mucosal haemorrhage; strangulation developing |
| Very late (> 24 hours) | Constant pain, peritonitis, septic shock, absent bowel sounds | Bowel necrosis, perforation, faecal peritonitis — surgical emergency |
(To be covered in the next section as per your request, but key differentials are listed here for completeness of context.)
Key differentials for the acute presentation [2]:
For rectal bleeding and vomiting:
- Meckel's diverticulum
- Malrotation with midgut volvulus (especially neonates — bilious vomiting)
- Bacterial colitis (infectious diarrhoea)
- Juvenile polyp (painless rectal bleeding)
For lethargy and altered consciousness:
- Sepsis / meningitis
- Non-accidental injury (NAI)
- Metabolic crisis (inborn error of metabolism)
For colicky abdominal pain in an infant:
- Incarcerated inguinal hernia (Indirect hernia due to patent processus vaginalis (PPV) — check inguinal regions!) [4]
- Infantile colic (diagnosis of exclusion, infant < 3 months)
- Testicular torsion (check scrotum in boys)
| Feature | Detail |
|---|---|
| Definition | Telescoping of proximal bowel (intussusceptum) into distal bowel (intussuscipiens) |
| Peak age | 4–24 months |
| Sex | Male > Female (3:2) |
| Most common site | Ileocolic / ileocaecal (85%) |
| Most common cause (children) | Idiopathic (reactive lymphoid hyperplasia of Peyer's patches) |
| Most common lead point (children) | Meckel's diverticulum |
| Adults | Always assume pathological lead point (r/o malignancy) |
| Classical triad | Colicky pain + red currant jelly stool + sausage-shaped mass (< 50%) |
| Key investigation | USG abdomen: target sign / pseudo-kidney sign |
| First-line treatment | Fluoroscopic/US-guided pneumatic reduction |
| Surgical indications | Failed reduction, peritonitis/necrosis, suspected pathological lead point |
High Yield Summary
-
Intussusception = telescoping of proximal bowel into distal bowel; most common cause of intestinal obstruction in infants aged 6–36 months.
-
Peak incidence 4–24 months; Male > Female; may be preceded by viral infection [1].
-
75–90% are idiopathic in children → reactive lymphoid hyperplasia of Peyer's patches (especially after viral URTI/GE). In adults, ALWAYS suspect a pathological lead point (malignancy until proven otherwise) [5].
-
Most common site: Ileocaecal intussusception (85%) [4].
-
Pathophysiology: Lead point caught by peristalsis → telescoping → mesenteric trapping → venous obstruction first (veins compress before arteries) → congestion → oedema → "red currant jelly stool" (LATE sign) → if untreated, arterial compromise → necrosis → perforation → peritonitis.
-
Classical triad (< 50%): intermittent colicky abdominal pain, red currant jelly stool, sausage-shaped mass in RUQ [4].
-
Don't forget: Lethargy/altered consciousness can be a presenting feature — do not miss intussusception in a lethargic infant!
-
Diagnosis: USG abdomen (diagnostic): target sign (axial), pseudo-kidney sign (longitudinal) [4].
-
Treatment: Fluoroscopic-guided pneumatic reduction (75–95% success) as first-line; surgery if failed, peritonitis, or suspected lead point [4].
-
Recurrence ~5–10%; recurrent episodes should prompt investigation for a pathological lead point.
Active Recall - Intussusception
[1] Lecture slides: GC 203. The child needs an operation Common emergencies and surgery in childhood.pdf (p45) [2] Senior notes: felixlai.md (Intussusception section) [3] Senior notes: Ryan Ho GI.pdf (p134) [4] Senior notes: maxim.md (Intussusception table, Section 4.3) [5] Senior notes: Ryan Ho GI.pdf (p134, adult intussusception) [6] Senior notes: Ryan Ho GI.pdf (p161, Meckel's diverticulum as lead point)
Differential Diagnosis of Intussusception
The differential diagnosis of intussusception is fundamentally about thinking through what else can cause this combination of symptoms in an infant/young child: episodic abdominal pain, vomiting (especially bilious), rectal bleeding, abdominal mass, and/or lethargy. The key is to organise differentials by the dominant presenting feature, because the presenting complaint determines your initial differential list.
The clinical features of intussusception overlap with several conditions. We can group differentials by the feature that most closely mimics intussusception:
Detailed Differential Diagnosis
| Condition | Key Distinguishing Features | Why It Mimics Intussusception | How to Differentiate |
|---|---|---|---|
| Malrotation with midgut volvulus | Bilious vomiting in a neonate (typically < 1 month) [7]; catastrophic if missed. Upper GI contrast shows abnormal DJ flexure position. Can present with PR bleed and abdominal distension [7]. | Both cause bilious vomiting, distension, and rectal bleeding. Midgut volvulus is a surgical emergency with very high risk of losing the entire midgut. | Age: volvulus peaks in neonates (first week of life), intussusception peaks 4–24 months. Speed: volvulus is typically acute and rapidly deteriorating. Investigation: upper GI contrast series shows malposition of DJ flexure (normally to the left of L1 vertebral body); USG may show "whirlpool sign" of twisted SMA. |
| Incarcerated inguinal hernia | Indirect hernia due to patent processus vaginalis (PPV) [4]; presents with erythema, pain & irritability, vomiting, cyanosis of the inguinal/scrotal mass. | Both cause colicky pain, vomiting, irritability in an infant. | Always examine the groins and scrotum in any child with intestinal obstruction. An incarcerated hernia is a clinical diagnosis — you will see and feel a tender, irreducible inguino-scrotal swelling. Intussusception mass is abdominal (usually RUQ), not inguinal. |
| Adhesive small bowel obstruction | History of prior abdominal surgery. Presents with classical intestinal obstruction: colicky pain, vomiting, distension, absolute constipation. | Both cause mechanical SBO symptoms. | History of previous surgery is key. AXR shows dilated SB loops with air-fluid levels but no specific "target sign." Post-operative intussusception (usually ileo-ileal) should also be considered — differentiated by USG [2]. |
| Hirschsprung's enterocolitis | Typically in a child with known or undiagnosed Hirschsprung's disease. Presents with abdominal distension, explosive foul-smelling diarrhoea, fever, sepsis. | Both can cause abdominal distension and bilious vomiting. | History of chronic constipation since birth, delayed passage of meconium (> 48 hours), failure to thrive. Rectal examination may produce explosive decompression. Rectal biopsy is diagnostic (absent ganglion cells). |
The Bilious Vomiting Neonate
Bilious (green) vomiting in a neonate is malrotation with midgut volvulus until proven otherwise — this is a surgical emergency. Do NOT confuse this with intussusception, which peaks at 4–24 months. A premature baby with greenish vomiting, PR bleed, and abdominal distension must have volvulus and necrotising enterocolitis high on the differential [7].
This is one of the most important differential groups because red currant jelly stool is a hallmark of intussusception but is a late sign. Several other conditions also cause rectal bleeding in children [2][4]:
| Condition | Key Distinguishing Features | Why It Mimics Intussusception | How to Differentiate |
|---|---|---|---|
| Meckel's diverticulum | Massive painless altered blood (maroon-coloured stool) due to acid secretion by ectopic gastric mucosa [4][8]. Can also cause IO via intussusception (as lead point), volvulus, or Littre's hernia. | Meckel's can cause intussusception (as a lead point), and independently causes rectal bleeding. | Painless vs. intussusception's painful bleeding. Meckel's bleeding is typically large-volume, maroon/dark red, and painless. Technetium-99m pertechnetate scan (Meckel's scan) detects ectopic gastric mucosa [4]. Meckel's diverticulitis: similar presentation as acute appendicitis; diagnosis by CT scan; may be incidental finding during appendicectomy [9]. |
| Juvenile colonic polyp | Painless rectal bleeding, typically small amount of bright red blood coating stool. 90% are juvenile polyps (benign hamartomas). | Both cause rectal bleeding in a young child. | Painless and no obstruction symptoms. Diagnosed by colonoscopy. Managed by endoscopic polypectomy or bedside suture ligation [4]. |
| Bacterial colitis | Infectious diarrhoea (Salmonella, Shigella, Campylobacter, EHEC) with bloody mucoid diarrhoea, fever, abdominal cramps. | Both cause bloody stools and abdominal pain. | Diarrhoea is the dominant feature (frequent, watery then bloody). Fever more prominent early. Stool culture is diagnostic. No palpable abdominal mass. No intermittent colicky pattern with pain-free intervals. |
| Intestinal duplication cyst | Congenital cystic or tubular duplication of bowel. Can contain ectopic gastric mucosa → peptic ulceration → bleeding. Can act as lead point for intussusception. | Both cause rectal bleeding; duplication cysts can cause intussusception. | USG may show a cystic structure adjacent to bowel wall with the characteristic "muscular rim sign" (gut signature). Definitive diagnosis often at surgery. |
| Anal fissure | Painful defecation with bright red blood on surface of stool or on wiping. History of constipation. | Both cause blood per rectum. | Blood is bright red and on the surface of stool (outlet-type bleeding), not mixed with mucus. Pain is specifically with defecation. Perianal inspection reveals the fissure. No abdominal symptoms [4]. |
Key distinguishing point for rectal bleeding: Intussusception bleeding is painful, small amount, with mucus ("red currant jelly"), whereas Meckel's diverticulum bleeding is painless, large amount, altered blood [4].
This is a critically important differential group because intussusception can present primarily with lethargy, and the abdominal pathology may be overlooked [2]:
| Condition | Key Distinguishing Features | Why It Mimics Intussusception | How to Differentiate |
|---|---|---|---|
| Septic shock | Fever, tachycardia, hypotension, altered consciousness, may have identifiable source (UTI, pneumonia, meningitis). | Both cause lethargy and pallor in an infant. Intussusception with advanced ischaemia can itself cause sepsis (bacterial translocation). | Intussusception lethargy is characteristically episodic — alternating with periods of inconsolable crying. Sepsis produces sustained lethargy. Always perform abdominal examination and consider USG if in doubt [2]. |
| Meningitis / Encephalitis | Fever, bulging fontanelle, neck stiffness (may be absent in infants), seizures, altered consciousness. | Both cause lethargy and irritability. | Lumbar puncture is diagnostic. The critical point is to not forget to examine the abdomen in a lethargic child — a simple USG abdomen can rule in/out intussusception rapidly. |
| Non-accidental injury (NAI) | Unexplained lethargy, bruising in non-mobile infant, subdural haematoma, retinal haemorrhages. | Both cause lethargy and irritability in an infant. | Detailed history (inconsistent story), full examination (bruising, burns), skeletal survey, ophthalmoscopy. Again, USG abdomen should be considered to exclude intussusception. |
| Metabolic crisis (IEM) | Inborn error of metabolism (e.g. urea cycle defect, organic acidaemia). Presents with poor feeding, vomiting, lethargy, encephalopathy, metabolic acidosis, hyperammonaemia. | Both cause vomiting and lethargy in an infant. | Blood gas (metabolic acidosis with high anion gap), ammonia level, lactate, urine organic acids, plasma amino acids. No abdominal mass; USG abdomen normal. |
Don't Forget the Abdomen in a Lethargic Infant
A lethargic infant may be worked up for sepsis or meningitis while intussusception is missed. Always palpate the abdomen and consider USG in any infant with unexplained episodic lethargy — the endorphin release from severe visceral pain can make the child appear "floppy" and unresponsive between episodes.
When intussusception presents late with peritonitis, or when the history is atypical, it can mimic conditions that cause RLQ pain and peritoneal irritation [3][4]:
| Condition | Key Distinguishing Features | Why It Mimics Intussusception | How to Differentiate |
|---|---|---|---|
| Acute appendicitis | Differential diagnosis of intussusception [3]. Peak 2nd–3rd decades but can occur in children. Periumbilical → RIF pain migration. Anorexia, nausea, low-grade fever. | Both cause abdominal pain and vomiting in children. Late intussusception with peritonitis can present with RIF tenderness. | Investigations: leucocytosis, plain XR (rarely), USG, CT (beware of high radiation) [1]. Appendicitis pain is progressive and constant (not colicky/episodic). No "pain-free intervals." No rectal bleeding typically. USG shows non-compressible, dilated appendix > 6mm. |
| Mesenteric adenitis | Viral illness prodrome; USG detects lymphadenopathy [4]. Caused by viral or bacterial infection (Yersinia, adenovirus) → mesenteric lymph node inflammation. | Both can follow a viral prodrome. Both cause abdominal pain in a child. | Pain is more diffuse and constant (not episodic/colicky). Child often looks well between painful episodes. USG shows clustered enlarged mesenteric lymph nodes (> 5mm short axis) without evidence of intussusception. Self-limiting. |
| Henoch-Schönlein purpura (HSP) | IgA-mediated small vessel vasculitis with palpable purpura (vasculitis + bleeding), abdominal pain (intestinal vasculitis vs intussusception), arthritis, renal involvement (GN) [4]. HSP can CAUSE intussusception (submucosal haemorrhage acts as lead point). | HSP causes severe colicky abdominal pain (intestinal vasculitis), and can itself cause intussusception. | Look for the classic rash — palpable purpura on buttocks and lower limbs. Arthritis/arthralgia. Abdominal pain in HSP: intestinal vasculitis vs intussusception — differentiated by USG [4]. If USG shows intussusception, treat accordingly. |
| Meckel's diverticulitis | Similar presentation as acute appendicitis; diagnosis by CT scan; incidental finding during appendicectomy [9]. | Both cause RLQ/periumbilical pain. Meckel's diverticulitis is clinically indistinguishable from appendicitis pre-operatively. | CT abdomen may show inflamed diverticulum in the distal ileum. Often discovered incidentally at laparoscopy/laparotomy for presumed appendicitis. Treatment: antibiotics; diverticulectomy / small bowel resection [9]. |
| Ovarian pathology (older girls) | Ovarian cyst torsion, ruptured ovarian cyst, ectopic pregnancy (adolescents). | Both cause acute lower abdominal pain. | Ask about LMP in adolescent girls. Pregnancy test (β-hCG). USG pelvis diagnostic. Girls: ask LMP, order PT & USG abdomen, do not PV on your own (consult Gynae!!) [4]. |
| Feature | Intussusception | Midgut Volvulus | Incarcerated Hernia | Meckel's (bleeding) | Appendicitis | HSP |
|---|---|---|---|---|---|---|
| Peak age | 4–24 months | Neonate (< 1 month) | Any age | < 2 years | 2nd–3rd decade | 3–10 years |
| Pain pattern | Episodic, colicky, pain-free intervals | Acute, constant, rapidly deteriorating | Constant, worsening | Painless (bleeding) or colicky (IO) | Progressive, constant | Colicky (vasculitis) |
| Vomiting | Bilious (late) | Bilious (early) | Yes | If IO present | Reflex, rarely bilious | Yes |
| Rectal bleeding | Red currant jelly (late) | Late, dark | No | Painless, maroon, large-volume | No (usually) | May occur |
| Mass | Sausage-shaped, RUQ | No specific mass | Inguinal/scrotal | No | No (unless abscess) | No |
| Rash | No | No | No | No | No | Palpable purpura (buttocks/legs) |
| Key investigation | USG: target sign | Upper GI contrast / USG whirlpool | Clinical diagnosis | Meckel's scan | USG / CT | USG (r/o intussusception) + clinical |
- Seasonal peaks: Intussusception in HK peaks in cooler months (October–February), coinciding with viral respiratory and GI seasons. Differentials such as bacterial colitis (Salmonella, Campylobacter) also peak in warmer months — a summer presentation of bloody diarrhoea is more likely infectious.
- HSP: Relatively common in HK children. Always examine the skin in any child with abdominal pain — the rash may appear after the abdominal symptoms, leading to diagnostic delay.
- Rotavirus vaccine: Now part of the HK childhood immunisation schedule. A very small excess risk of intussusception within 1 week of the first dose should be in the history if the timeline fits.
High Yield Summary
-
Organise differentials by dominant presenting feature: intestinal obstruction, rectal bleeding, lethargy, or RLQ/peritoneal signs.
-
Bilious vomiting in a neonate = malrotation with midgut volvulus until proven otherwise — do NOT confuse with intussusception (different age group).
-
Always examine the groins — incarcerated inguinal hernia (due to patent processus vaginalis) is a common mimic of intestinal obstruction in infancy.
-
Rectal bleeding differentiation: Intussusception = painful, small amount, mucus; Meckel's diverticulum = painless, large amount, altered blood [4].
-
HSP can CAUSE intussusception — differentiate intestinal vasculitis pain from intussusception using USG [4].
-
Meckel's diverticulitis: similar presentation as acute appendicitis; diagnosis by CT scan; may be incidental finding at appendicectomy [9].
-
Lethargy as a presenting feature: always think intussusception in a lethargic 6–24 month old infant — don't be misled into a sepsis/meningitis work-up without examining the abdomen and obtaining USG.
-
Key differentiators: Age of presentation, pain pattern (episodic vs constant), presence/absence of mass, location of mass (abdominal vs inguinal), rash (HSP), and USG findings.
Active Recall - Differential Diagnosis of Intussusception
References
[1] Lecture slides: GC 203. The child needs an operation Common emergencies and surgery in childhood.pdf (p41, p45) [2] Senior notes: felixlai.md (Intussusception section — Differential diagnosis) [3] Senior notes: felixlai.md (Intestinal malrotation section — Differential diagnosis listing intussusception) [4] Senior notes: maxim.md (Paediatric surgical abdomen table; LGIB section; HSP section) [5] Senior notes: Ryan Ho GI.pdf (p134) [7] Lecture slides: Case Study – Paediatric Surgery Bilious vomiting of new-born _ACH Fung.pdf (p5) [8] Senior notes: felixlai.md (Meckel's diverticulum — Clinical manifestation) [9] Lecture slides: GC 195. Lower and diffuse abdominal pain RLQ problems; pelvic inflammatory disease; peritonitis and abdominal emergencies.pdf (p22)
Diagnosis of Intussusception
The diagnosis of intussusception rests on a high index of clinical suspicion combined with rapid imaging confirmation. There are no formal "diagnostic criteria" in the way that rheumatological or metabolic conditions have — rather, the diagnosis is made by recognising the clinical pattern and confirming with imaging. The key principle is: if you think of it, ultrasound it — because early diagnosis and reduction before ischaemia sets in dramatically improves outcomes.
While there is no formal points-based scoring system, the clinical diagnosis relies on recognising the characteristic pattern:
| Feature | Diagnostic Value |
|---|---|
| Age 4–24 months | High pre-test probability |
| Episodic colicky pain with pain-free intervals | Most consistent early feature |
| Bilious vomiting | Suggests distal SBO |
| Red currant jelly stool | Late sign — highly suggestive but present in minority at presentation |
| Sausage-shaped RUQ mass | When present, virtually diagnostic |
| Dance's sign (empty RIF) | Supportive |
| Preceding viral illness (URTI/GE) | Supports idiopathic aetiology |
In practice: Any infant aged 6–24 months with episodic inconsolable crying (especially drawing up of legs) ± vomiting should have intussusception considered. The threshold for obtaining an ultrasound should be very low — it is non-invasive, radiation-free, and near-100% sensitive in experienced hands.
There Is No 'Diagnostic Criteria' Checklist
Unlike conditions such as rheumatic fever (Jones criteria) or SLE (SLICC criteria), intussusception does not have a validated points-based scoring system. The "diagnostic criterion" is clinical suspicion + confirmatory imaging (USG). The classical triad is present in fewer than 50% of cases, so waiting for the full triad before investigating is a dangerous approach.
The following algorithm represents the standard approach in a Hong Kong paediatric surgical unit:
3. Investigation Modalities
The investigations for intussusception serve three purposes:
- Confirm the diagnosis (primarily USG)
- Assess for complications (ischaemia, perforation, dehydration)
- Identify pathological lead points (USG, CT)
| Investigation | Purpose | Key Findings / Interpretation |
|---|---|---|
| Urinalysis, pregnancy test [10] | Rule out urological causes of abdominal pain; pregnancy test in adolescent girls | Should be normal in intussusception. Haematuria may suggest HSP (renal involvement) |
| PR examination | Detect blood/mucus before it is passed spontaneously; assess rectal masses | "Red currant jelly" on examining finger is highly suggestive. May also detect a prolapsing intussusceptum in advanced cases. |
| Vital signs | Assess haemodynamic status, fever, dehydration | Tachycardia and prolonged CRT suggest dehydration/shock. Fever suggests complication (necrosis, perforation, peritonitis). |
Blood tests: Blood count, renal and liver function, amylase, clotting profile, arterial blood gas, type and screen [10]
| Investigation | Rationale (Why?) | Key Findings in Intussusception |
|---|---|---|
| CBC (FBC) | Assess for infection (raised WCC with left shift suggests complication); baseline Hb for bleeding; platelet count pre-operatively | WBC for infection (inflammatory source may cause left shift on differential) [11]. Leucocytosis suggests complicated intussusception (necrosis, peritonitis). Anaemia if significant GI blood loss. |
| RFT (Renal function tests) | Assess hydration status; baseline creatinine if contrast study considered | Hydration status; HypoK/hypoCl from prolonged vomiting [11]. Elevated urea:creatinine ratio suggests pre-renal dehydration from vomiting and third-space losses. |
| Electrolytes | Prolonged vomiting → electrolyte derangement | Hypokalaemia (K⁺ loss in vomitus + metabolic alkalosis shifts K⁺ intracellularly + renal K⁺ wasting from RAAS activation). Hypochloraemia and metabolic alkalosis from loss of gastric HCl. Hyponatraemia from third-spacing and vomiting [8]. |
| LFT | Rule out hepatobiliary pathology as cause of abdominal pain; baseline pre-surgery | Usually normal. May be deranged if prolonged shock with hepatic hypoperfusion. |
| Clotting profile + Type & Screen | Pre-operative preparation; crossmatch if surgery anticipated | Essential if surgery is likely. Ensures blood is available for transfusion. |
| Amylase [10] | Rule out pancreatitis as a cause of abdominal pain (pancreatitis can cause secondary ileus) | Amylase: peaks at 6-24h, > 1000 diagnostic of acute pancreatitis [11]. Should be normal in intussusception. |
| ABG (Arterial blood gas) [10] | Assess acid-base status; lactate level as marker of bowel ischaemia | Metabolic acidosis, raised lactate → intestinal ischaemia [11]. A raised lactate (> 2 mmol/L) should raise alarm for bowel compromise. Metabolic alkalosis → prolonged vomiting [11]. |
| Serum lactate | Sensitive marker of tissue hypoperfusion and bowel ischaemia | Elevated lactate in intussusception suggests strangulation with ischaemia — this is an indication for urgent surgical intervention rather than attempting non-operative reduction [8]. |
Lactate and ABG in Intussusception
A raised serum lactate or metabolic acidosis on ABG should prompt you to think about bowel ischaemia/strangulation. In a child with suspected intussusception and raised lactate, do NOT delay for non-operative reduction attempts — this child may need urgent surgery. Conversely, metabolic alkalosis with hypokalaemia and hypochloraemia simply reflects prolonged vomiting.
3.3 Imaging Investigations
AXR — may show dilated small bowels and a mass [1].
Role: AXR is usually the first imaging obtained, primarily to exclude perforation (pneumoperitoneum) and to look for signs of intestinal obstruction. However, AXR is neither sensitive nor specific for intussusception — a normal AXR does NOT exclude the diagnosis. Its main value is to identify complications and provide a global overview.
Erect CXR for free gas under diaphragm → perforation [10][11]
| AXR Finding | Description | Pathophysiological Basis |
|---|---|---|
| Dilated small bowel loops | Proximal SB loops > 3cm diameter with air-fluid levels on erect film | Mechanical obstruction at the ileocaecal junction → proximal bowel cannot empty → gas and fluid accumulate → dilatation |
| Absence of colonic (LB) gas | No gas seen in the large bowel | The intussusception obstructs the ileocaecal junction → gas cannot pass into the colon → the colon "empties" distally. AXR: distended SB, absent LB gas [4]. |
| "Target sign" (AXR) | Two concentric radiolucent circles superimposed on the right kidney | The peritoneal fat surrounding and within the intussusception creates concentric radiolucent rings. This is seen because fat is less dense than soft tissue and the layers of bowel-within-bowel create a characteristic pattern [2]. |
| "Crescent sign" | Soft-tissue density projecting into the gas of the large bowel | The intussusceptum (a soft-tissue mass) protrudes into the gas-filled lumen of the colon, creating a crescentic soft-tissue opacity outlined by colonic gas [2]. |
| "Sausage-shaped opacity" | Elongated soft-tissue density in the RUQ/transverse colon area | The telescoped bowel mass itself, visible as a soft tissue density [5]. |
| Pneumoperitoneum | Free gas under diaphragm on erect CXR, or Rigler's sign on supine AXR | Indicates bowel perforation — absolute contraindication to enema reduction → proceed directly to surgery |
| Air-fluid levels | Multiple (> 5) air-fluid levels on erect AXR | Indicates intestinal obstruction. > 5 air-fluid levels diagnostic of IO [5][11]. |
AXR Limitations in Intussusception
AXR has a sensitivity of only ~45–80% for intussusception. A normal AXR does NOT exclude intussusception. If clinical suspicion is present, proceed directly to USG regardless of AXR findings. The main role of AXR is to exclude perforation (pneumoperitoneum) before attempting enema reduction.
Ultrasound — usually diagnostic in experienced hands [1].
USG abdomen (diagnostic): target sign, pseudo-kidney sign [4].
Why USG is the investigation of choice:
- Sensitivity and specificity approach 100% in experienced hands [2]
- Non-invasive, no radiation (critical in paediatric population)
- Can detect pathological lead points (masses, Meckel's diverticulum, duplication cysts)
- Can assess vascularity of the intussusceptum (Doppler) → predict viability
- Can monitor the success of reduction in real-time
- Readily available in most Hong Kong hospitals with paediatric services
| USG Finding | View | Description | Pathophysiological Basis |
|---|---|---|---|
| "Target sign" ("Doughnut sign" / "Bull's eye sign") | Transverse (axial) view | Multiple concentric rings of alternating echogenicity | In cross-section, the layers of the intussusceptum (mucosa, submucosa, muscularis, serosa) and the intussuscipiens create concentric rings. The oedematous, hyperaemic mucosa and the mesenteric fat trapped between layers create the alternating hypo- and hyperechoic rings — like a "target" or "doughnut" [2][4]. |
| "Pseudo-kidney sign" ("Sandwich sign") | Longitudinal (sagittal) view | An elongated mass with layers resembling the cortex and hilum of a kidney | In longitudinal section, the layered appearance of bowel-within-bowel with the trapped mesentery (hyperechoic) resembles the renal parenchyma surrounding the echogenic hilum — hence "pseudo-kidney" [2][4]. |
| Trapped mesenteric fat and lymph nodes | Both views | Echogenic focus within the intussusception | The dragged mesentery contains hyperechoic fat and hypoechoic lymph nodes, visible between the layers of the intussusception |
| Free fluid | General survey | Anechoic fluid around the intussusception or in the pelvis | Transudation from congested bowel; larger amounts suggest more advanced disease |
| Absent Doppler flow in intussusceptum | Colour Doppler | No vascular signal in the trapped bowel wall | Lack of perfusion in intussusceptum indicates development of ischaemia [2]. This is a poor prognostic sign — suggests arterial compromise and possible necrosis. May influence decision to proceed directly to surgery rather than attempting enema reduction. |
| Pathological lead point | Variable | A discrete mass within the intussusception | If a structural lesion (polyp, Meckel's diverticulum, lymphomatous mass, duplication cyst) is identified, it should prompt surgical exploration rather than enema reduction, as the lead point will cause recurrence and may itself require definitive treatment [2]. |
| Length of intussusception | Longitudinal | Measured in cm | Longer intussusceptions (> 3.5 cm) may be associated with lower success rates of pneumatic reduction, though this is not an absolute cut-off. |
How to interpret USG in context:
USG Findings That Favour Surgery Over Enema Reduction
The following USG findings should make you lean toward surgical intervention rather than attempting non-operative reduction:
- Absent Doppler flow in the intussusceptum (ischaemia)
- Large amount of free fluid (suggests advanced disease)
- Visible pathological lead point (will cause recurrence; may need resection)
- Very long intussusception extending to the left colon
- Trapped fluid between layers of the intussusception (suggests significant oedema/necrosis)
CT: characteristic target (donut) lesions [5].
Role: CT is NOT first-line for paediatric intussusception due to radiation exposure. It is reserved for specific situations [2]:
| Indication for CT | Rationale |
|---|---|
| USG equivocal or technically limited | Obese child, excessive bowel gas, operator-dependent limitations |
| Atypical presentation (older child / adult) | Higher likelihood of pathological lead point; need to characterise the lesion and assess for malignancy |
| Suspected complications | Evaluate for perforation, abscess, or extent of ischaemia when clinical picture is unclear |
| Post-operative intussusception | Ileo-ileal intussusception may be difficult to detect on USG |
| CT Finding | Description | Pathophysiological Basis |
|---|---|---|
| "Target sign" / "Donut sign" | Alternating hypodense and hyperdense concentric layers on axial cuts | Same principle as USG target sign — layers of bowel wall, mesentery, and lumen creating concentric rings. Fat (hypodense) alternates with enhanced bowel wall (hyperdense after IV contrast) [5][8]. |
| "Sausage-shaped mass" | Elongated soft-tissue mass in the colon | The intussusception mass seen in coronal or sagittal reformats |
| Identification of lead point | Discrete enhancing mass within the intussusception | Critical for surgical planning — characterise the lesion (polyp, lymphoma, Meckel's, GIST, carcinoma in adults) |
| Bowel wall thickening | Thickened, oedematous bowel wall | Venous congestion → oedema |
| Reduced/absent bowel wall enhancement | Lack of contrast uptake in the intussusceptum wall | Arterial compromise → ischaemia → non-viable bowel [8] |
| Pneumatosis intestinalis | Gas within the bowel wall | Transmural necrosis → gas-producing bacteria infiltrate the bowel wall [8] |
| Portal venous gas | Gas in the portal venous system | Extremely ominous sign — indicates advanced bowel necrosis with gas entering the mesenteric venous system and draining to the portal vein [8] |
| Free fluid / pneumoperitoneum | Intraperitoneal fluid or free air | Perforation (free air) or transudation from ischaemic bowel (free fluid) |
Contrast enema — rarely done now [1] for purely diagnostic purposes.
Historical context: Before the widespread availability of USG, contrast enema (barium or air) was the primary diagnostic tool. Fluoroscopic contrast enema would show:
- "Claw sign" / "Meniscus sign": The contrast (barium or air) outlines the tip of the intussusceptum within the colon, creating a crescent/claw-shaped filling defect.
- "Coiled spring" appearance: Contrast tracks between the layers of the intussusception, outlining the concentric rings.
Current role: In modern practice, contrast enema is used almost exclusively as a therapeutic tool (pneumatic or hydrostatic reduction) rather than for diagnosis. The diagnosis is made by USG, and the enema is then performed as treatment. Some centres use fluoroscopy during pneumatic reduction to monitor progress.
Role: Not used for diagnosing intussusception per se, but indicated when recurrent intussusception raises suspicion of a Meckel's diverticulum as a pathological lead point [4][12].
- Principle: Pertechnetate (⁹⁹ᵐTc) behaves like chloride ions → actively accumulated and secreted by gastric mucosa. If ectopic gastric mucosa is present in a Meckel's diverticulum, the isotope accumulates there, creating a "hot spot" in the right lower quadrant.
- Requires pre-medication with H2 blockers: These inhibit excretion of the isotope into the bowel lumen (which would cause dilution and false negatives), while NOT inhibiting uptake by the mucosa [4].
- Limitations: False positives (intestinal duplication cysts with gastric mucosa), false negatives (insufficient ectopic gastric mucosa, rapid GI bleeding diluting the tracer) [4].
In adults, the diagnostic approach differs fundamentally because intussusception in adults is ALWAYS associated with pathological lead-points [5]:
| Modality | Role in Adults |
|---|---|
| CT abdomen with contrast | First-line in adults (unlike children where USG is first-line). Identifies the intussusception, characterises the lead point, stages malignancy, and assesses for metastatic disease. |
| Colonoscopy | May be used if colonic intussusception is suspected, to biopsy a visible lead point. However, avoid insufflation near an obstructed segment. |
| MRI | Occasionally used for further characterisation of identified lesions, especially in younger adults where radiation avoidance is desirable. |
Adults: usually require formal resection to r/o CA [5] — the primary goal in adults is to identify and resect the lead point, not to perform non-operative reduction.
| Investigation | Key Findings | Sensitivity/Specificity | When to Use |
|---|---|---|---|
| AXR | Dilated SB, absent LB gas, target sign, crescent sign, sausage-shaped opacity | Low sensitivity (~45-80%) | First-line to exclude perforation; not definitive |
| USG abdomen | Target sign (axial), pseudo-kidney sign (longitudinal), Doppler assessment, lead point detection | ~100% in experienced hands | Investigation of choice in children |
| CT abdomen | Target/donut sign, lead point characterisation, complications (ischaemia, perforation) | Very high | Atypical cases, older children, adults, equivocal USG |
| Contrast enema | Claw sign, meniscus sign, coiled spring | High but largely replaced by USG | Now mainly therapeutic, rarely done for diagnosis |
| Erect CXR | Pneumoperitoneum (free gas under diaphragm) | High for perforation | Must be done before enema reduction to exclude perforation |
| Meckel's scan | Hot spot in RLQ (ectopic gastric mucosa) | Moderate (sensitivity ~85% in children) | Recurrent intussusception suspected to be from Meckel's |
High Yield Summary
-
There are no formal "diagnostic criteria" for intussusception — diagnosis is clinical suspicion + imaging confirmation.
-
USG abdomen is the investigation of choice: target sign (axial) and pseudo-kidney sign (longitudinal), with sensitivity and specificity approaching 100% in experienced hands [1][2][4].
-
AXR is done first to exclude perforation (pneumoperitoneum) before enema reduction, and may show dilated SB with absent LB gas, but a normal AXR does NOT exclude intussusception.
-
CT is reserved for atypical cases, adults (first-line in adults), and when a pathological lead point needs characterisation. Shows characteristic target (donut) lesions [5].
-
Contrast enema is rarely done now [1] for diagnosis — it is primarily a therapeutic tool.
-
Key USG danger signs favouring surgery: absent Doppler flow (ischaemia), visible lead point, large free fluid.
-
Blood tests serve to assess for complications: raised lactate/metabolic acidosis → bowel ischaemia; electrolyte derangement from vomiting; leucocytosis suggesting complication.
-
In adults, CT with contrast is first-line, and the goal is to identify and resect the pathological lead point (usually malignancy).
Active Recall - Diagnosis of Intussusception
References
[1] Lecture slides: GC 203. The child needs an operation Common emergencies and surgery in childhood.pdf (p47) [2] Senior notes: felixlai.md (Intussusception — Diagnosis section) [4] Senior notes: maxim.md (Intussusception table; Meckel's scan section) [5] Senior notes: Ryan Ho GI.pdf (p134) [8] Senior notes: felixlai.md (Meckel's diverticulum — Diagnosis/biochemical tests) [10] Lecture slides: GC 195. Lower and diffuse abdominal pain RLQ problems; pelvic inflammatory disease; peritonitis and abdominal emergencies.pdf (p12, p29) [11] Senior notes: Ryan Ho GI.pdf (p105–106); Ryan Ho Fundamentals.pdf (p279) [12] Senior notes: maxim.md (Meckel's scan — Investigations)
Management of Intussusception
The management of intussusception follows a clear logical hierarchy: resuscitate → assess → reduce. The cornerstone principle is that most paediatric intussusceptions can be reduced non-operatively with pneumatic or hydrostatic enema, achieving success rates of 75–95%. Surgery is reserved for specific indications. The urgency of management depends on the duration of symptoms and the presence of complications — the longer the delay, the higher the risk of ischaemia, necrosis, and the need for bowel resection.
In adults, the approach is fundamentally different: adults usually require formal resection to r/o CA [5].
Before ANY attempt at reduction, the child must be adequately resuscitated. This follows the general "drip and suck" principle of intestinal obstruction management [8][13]:
| Intervention | Rationale (Why?) | Details |
|---|---|---|
| NPO (Nil per os) | Limits further bowel distension; prepares for potential anaesthesia/surgery | All patients should be made NPO immediately [8] |
| IV fluid resuscitation | Replace losses from vomiting, third-spacing, and reduced intake. Correct intravascular depletion before reduction attempts. | Crystalloids such as normal saline (NS), Ringer's lactate or Hartmann's solution [8]. In children: NS 20 mL/kg bolus repeated as needed. K⁺ replacement may be indicated but should be given cautiously in patients with AKI from severe dehydration [8]. |
| NG tube decompression | Decompress the proximal obstructed bowel; reduce risk of aspiration during sedation/anaesthesia | Placed on free drainage with 4-hourly aspiration [8]. Functions: (1) Decompression proximal to obstruction; (2) Reduce aspiration risk during induction of anaesthesia [8]. |
| Prophylactic antibiotics | Bacterial translocation across ischaemic bowel wall; preparation for possible surgery | Broad-spectrum antibiotics due to bacterial overgrowth; mandatory for all patients undergoing surgery for intestinal obstruction [8]. Typical regimen: IV amoxicillin/clavulanate or cefuroxime + metronidazole. Prophylactic antibiotics may be given due to risk of perforation [2]. |
| Pain relief | Humane care; also reduces vagal response that can complicate reduction | Pain management with opioids is reasonable although pain from mechanical bowel obstruction in general is often not amenable to treatment with analgesics [8]. IV paracetamol ± IV morphine 0.1 mg/kg in children, titrated carefully. |
| Monitoring | Track response to resuscitation; detect deterioration early | Vital signs (HR, BP, SpO₂, temp), urine output (catheterise if critically ill), serial abdominal examination |
Resuscitation Before Reduction
Never attempt enema reduction in a dehydrated, haemodynamically unstable child. Adequate resuscitation with IV fluids and correction of electrolyte abnormalities is essential first. A child who arrests during enema reduction due to unrecognised hypovolaemia is a preventable tragedy.
3. Non-Operative Reduction (First-Line Treatment)
This is the preferred first treatment with high success rate in most cases [2].
Non-operative reduction works by applying retrograde pressure (air or fluid) into the colon via the rectum, which pushes the intussusceptum back through the intussuscipiens in the reverse direction of the original telescoping. Think of it as "un-telescoping" the bowel by pushing from below.
There are two main techniques, and two main guidance modalities:
| Pneumatic reduction (air) | Hydrostatic reduction (fluid) | |
|---|---|---|
| Medium | Air (or CO₂) | Normal saline (or barium historically) |
| Guidance | Fluoroscopy (traditional) or USG | USG (preferred) or fluoroscopy |
| Mechanism | Air insufflated per rectum → retrograde pressure pushes intussusceptum back | Saline infused per rectum under gravity → hydrostatic pressure reduces intussusception |
| Advantages | Pneumatic technique using air or CO₂ reduces intussusception more easily and is more advantageous if perforation occurs [2] (air causes less peritoneal contamination than barium; tension pneumoperitoneum can be rapidly decompressed with needle) | USG-guided hydrostatic reduction avoids radiation entirely; real-time visualisation of reduction |
| Success rate | 75–95% success rate [4] | Similar success rates (~80–95%) |
Fluoroscopic-guided pneumatic reduction (75–95% success rate): instill gas with 18–22 Fr Foley → maintain pressure ~100–120 mmHg × 3 min → observe for gush of air into terminal ileum [4].
- Preparation: Child is resuscitated, IV access secured, NG in situ. Surgeon and anaesthetist must be on standby (in case of perforation requiring emergency laparotomy). Erect CXR done beforehand to exclude pre-existing pneumoperitoneum.
- Catheter insertion: 18–22 Fr Foley catheter inserted into the rectum; balloon inflated to create a seal (prevents air leak) [4].
- Air insufflation: Air is insufflated via a hand pump or controlled insufflator, connected to a pressure gauge.
- Pressure maintenance: Maintain pressure ~100–120 mmHg for ~3 minutes [4]. The pressure must not exceed 120 mmHg (risk of perforation rises steeply above this).
- Monitoring: Under fluoroscopy, the intussusceptum is seen as a soft tissue mass outlined by air. As reduction proceeds, the mass retreats toward the ileocaecal valve.
- Endpoint of successful reduction: Observe for gush of air into terminal ileum — this is the definitive sign that the intussusception has been completely reduced [4]. Other markers of success include: appearance of water and bubbles in terminal ileum, free flow of contrast or air into terminal ileum, relief of symptoms, disappearance of abdominal mass [2].
- If unsuccessful: A single attempt may be repeated (up to 3 attempts total is the general consensus). Between attempts, allow a rest period of 15–30 minutes (the oedema may settle slightly, improving the chance of success on the next attempt).
- Increasingly popular in Hong Kong and globally as it avoids radiation entirely.
- Ultrasound is now the intervention of choice for guidance [2].
- Warm normal saline is infused per rectum under gravity (height of the saline bag provides the hydrostatic pressure, typically hung ~100 cm above the patient).
- The USG operator watches the intussusception reduce in real-time — the "target sign" progressively disappears, and eventually free fluid is seen flowing into the terminal ileum.
- Advantages over fluoroscopy: No radiation, real-time monitoring of bowel wall viability (Doppler), better visualisation of complete reduction, ability to detect residual intussusception or lead points.
| Criteria | Explanation |
|---|---|
| Confirmed intussusception on USG | Diagnosis must be certain before attempting |
| No signs of peritonitis | Peritonitis suggests perforation or necrosis → surgery needed |
| No pneumoperitoneum on erect CXR | Perforation is an absolute contraindication to enema |
| Haemodynamically stable after resuscitation | Unstable child → surgery |
| Duration ideally < 48 hours | Longer duration → higher risk of necrosis → lower success rate |
| No suspected pathological lead point | Lead points will cause recurrence; need surgical excision |
| Contraindication | Rationale |
|---|---|
| Pneumoperitoneum (perforation) | Insufflation of air/fluid through a perforated bowel → faecal peritonitis or tension pneumoperitoneum |
| Peritonitis / necrosis [4] | Necrotic bowel cannot safely be "pushed back" — it will perforate during reduction. Needs resection. |
| Haemodynamic instability / septic shock | Child is too unstable for a controlled enema procedure; needs laparotomy |
| Recurrent intussusception with suspected lead point | Reduction alone will not be curative; the lead point needs surgical excision |
| Factor | Consideration |
|---|---|
| Duration > 48 hours | Lower success rate, higher complication risk, but not an absolute contraindication |
| Very young infant (< 3 months) | Higher likelihood of a pathological lead point; lower success rate |
| Ileo-ileal intussusception | Less likely to respond to non-operative reduction [2] — the enema pressure cannot effectively reach the small bowel |
| Absent Doppler flow on USG | Suggests ischaemia — may proceed cautiously but have very low threshold for surgery |
| Complication | Incidence | Details |
|---|---|---|
| Bowel perforation | < 1% [2]; Cx: bowel perforation, tension pneumoperitoneum [4] | Risk factors include age < 6 months, long duration of symptoms and higher pressure during reduction [2]. Presents with sudden clinical deterioration, abdominal distension, desaturation. If pneumatic reduction → tension pneumoperitoneum requiring immediate needle decompression (large-bore needle in RUQ) followed by emergency laparotomy. |
| Recurrence | ~5% [4] | Due to residual bowel oedema acting as a transient lead point. Most recurrences happen within 72 hours. Recurrent episodes can be managed with repeat enema reduction (success rate is similar). Multiple recurrences should prompt investigation for a pathological lead point. |
Post-reduction management: Observation with hospitalisation for 12–24 hours [2]:
| Aspect | Details | Rationale |
|---|---|---|
| Hospitalisation | Observe in hospital for 12–24 hours minimum | Monitor for recurrence and complications |
| NG tube | Nasogastric suction is maintained until bowel function has returned and patient has passage of a bowel movement [2] | Ensure bowel function recovers before feeding |
| Feeding | Gradual introduction of clear fluids → milk/diet as tolerated | Prevents vomiting from feeding too early |
| Fever | Patient usually presents with fever after successful reduction due to bacterial translocation or release of endotoxin or cytokines [2] | Reassure parents — post-reduction fever is expected and self-limiting. However, persistent high fever may indicate incomplete reduction or complication. |
| Recurrence monitoring | Possibility to develop recurrent intussusception due to residual bowel inflammation which may itself act as pathological lead point [2] | Educate parents on symptoms to watch for; seek urgent medical attention if symptoms recur |
4. Surgical Management
Surgical reduction: indicated if [4]:
- Failed pneumatic reduction (after up to 3 attempts)
- Peritonitis / necrosis
- Suspected pathological lead points
Additional surgical indications [2]: 4. Suspected intussusception who is critically ill [2] 5. Suspected bowel perforation [2] 6. Refractory to non-operative reduction [2] 7. Post-operative (ileo-ileal) intussusception — not amenable to enema reduction 8. Adult intussusception — adults usually require formal resection to r/o CA [5]
| Approach | Details |
|---|---|
| Laparotomy (traditional) | Right transverse or midline incision. Allows full exploration of the abdomen, manual reduction, assessment of bowel viability, and resection if needed. Remains the standard in many centres, especially in emergency settings. |
| Laparoscopy | Increasingly used in stable patients with uncomplicated intussusception. Advantages: smaller incisions, faster recovery, better cosmesis. Limitations: may not be feasible if significant distension or adhesions; requires experienced laparoscopic surgeon. Convert to open if needed. |
Manual reduction at operation is attempted in most cases but resection with primary anastomosis may be needed if manual reduction is not possible or a lead point is identified [2].
The operative steps follow a logical sequence:
-
Operative decompression (always performed first):
- Milk SB content in retrograde manner to stomach → insert orogastric tube for aspiration → replace aspirated volume as measured [13].
- This decompresses the dilated proximal bowel, improving surgical access and reducing the risk of post-operative ileus.
-
Manual reduction (Hutchinson's manoeuvre):
- The surgeon applies gentle, sustained retrograde pressure on the intussuscipiens (the distal "receiving" bowel) to push the intussusceptum back out — like squeezing toothpaste back into the tube.
- Critical rule: Never PULL on the intussusceptum (this will tear the oedematous, friable bowel). Always PUSH from below.
- Continue squeezing gently until the intussusceptum is fully delivered back through the ileocaecal valve.
-
Assessment of bowel viability after reduction:
- Inspect the reduced bowel for colour (pink = viable; dark purple/black = necrotic), peristalsis, mesenteric pulsations.
- Wrap in warm saline-soaked packs and wait 10–15 minutes to reassess if borderline.
-
Decision regarding resection:
| Scenario | Action |
|---|---|
| Bowel is viable, no lead point | Reduction alone is sufficient. Close the abdomen. |
| Bowel is viable but lead point identified | Reduce the intussusception, then resect the lead point (e.g., Meckel's diverticulectomy, polypectomy, segmental resection) with primary anastomosis |
| Bowel is necrotic or irreducible | Resection with primary anastomosis [2][13]. The non-viable segment is resected and a primary end-to-end or end-to-side anastomosis is performed. In rare cases of severe contamination/peritonitis, a temporary stoma may be necessary (ileostomy) with delayed anastomosis. |
-
Incidental appendicectomy: Some surgeons perform a prophylactic appendicectomy during the procedure, as the caecum is already mobilised. This is not universally practised.
-
Histological examination: All resected specimens (bowel, lead points) should be sent for histology to exclude lymphoma, GIST, or other pathology.
| Aspect | Details |
|---|---|
| NPO until resolution | Continue NPO, NG decompression until bowel function returns (passage of flatus/stool) [13] |
| IV fluid/electrolytes | Continue IV maintenance fluids; give Ringer's lactate/NS ± K⁺ supplements and correct acidosis [13] |
| Antibiotics | Continue IV antibiotics for 3–5 days (longer if peritonitis or bowel resection performed) |
| Nutritional support | If prolonged NPO (> 5–7 days), consider parenteral nutrition. Enteral feeding is always first choice if GI tract can be used safely [14]. Resume enteral feeds as soon as bowel function recovers. |
| Wound care | Standard surgical wound care; watch for wound infection |
| Follow-up | Outpatient review at 1–2 weeks; histology results if resection performed |
The approach in adults is fundamentally different [5]:
| Principle | Details |
|---|---|
| Assume pathological lead point | Adults: ALWAYS associated with pathological lead-points (usually intraluminal lesions in SB), e.g., polyp, submucosal lipoma, Meckel's diverticulum, GIST, carcinoma [5] |
| CT first | CT abdomen with contrast is first-line (not USG) — characterise the lead point, assess for malignancy, stage disease |
| Surgical resection | Adults usually require formal resection to r/o CA [5]. Non-operative reduction is NOT appropriate because: (1) the lead point will cause recurrence; (2) malignancy must be excluded by histology; (3) reducing a tumour may risk seeding. |
| Oncological principles | If malignancy is suspected, resection should follow oncological principles (adequate margins, lymph node harvest, en bloc resection of involved mesentery). |
| Situation | Management |
|---|---|
| Typical infant, no complications | Resuscitate → USG confirms → pneumatic/hydrostatic enema reduction (75–95% success) → observe 12–24h |
| Failed enema reduction (×3) | Surgical reduction ± resection |
| Peritonitis / perforation / shock | Emergency laparotomy — do NOT attempt enema |
| Suspected pathological lead point | Surgical exploration and resection |
| Recurrent intussusception | First recurrence: repeat enema reduction is reasonable. Multiple recurrences: investigate for lead point → surgical exploration |
| Post-operative (ileo-ileal) | Surgical reduction (enema cannot reach small bowel) |
| Adult | CT staging → formal surgical resection to r/o malignancy |
High Yield Summary
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Resuscitate first: "Drip and suck" — NPO, IV fluids (NS/Ringer's lactate), NG decompression, prophylactic antibiotics, correct electrolytes [8][13].
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First-line treatment: Fluoroscopic/USG-guided pneumatic (or hydrostatic) reduction — success rate 75–95% [4]. USG is now the intervention of choice for guidance [2].
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Pneumatic reduction technique: 18–22 Fr Foley catheter, maintain pressure ~100–120 mmHg × 3 min, observe for gush of air into terminal ileum [4].
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Absolute contraindications to enema reduction: peritonitis/necrosis, pneumoperitoneum (perforation), haemodynamic instability, suspected pathological lead point.
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Surgical indications: (1) Failed pneumatic reduction; (2) Peritonitis / necrosis; (3) Suspected pathological lead points [4].
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Surgical approach: Manual reduction (Hutchinson's manoeuvre — PUSH, don't PULL) → assess viability → resection with primary anastomosis if necrotic or irreducible [2][13].
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Post-reduction: Observe 12–24h; expect post-reduction fever (bacterial translocation); NG suction until bowel function returns; recurrence rate ~5–10% [2][4].
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Adults: always formal surgical resection to r/o CA — non-operative reduction is NOT appropriate [5].
Active Recall - Management of Intussusception
References
[2] Senior notes: felixlai.md (Intussusception — Treatment section) [4] Senior notes: maxim.md (Intussusception table — Management) [5] Senior notes: Ryan Ho GI.pdf (p134 — adult intussusception management; p139 — surgical management of IO) [8] Senior notes: felixlai.md (Supportive management of IO — NPO, IV fluid, NG tube, antibiotics, pain relief) [13] Senior notes: Ryan Ho GI.pdf (p138–139 — Supportive management and surgical management of IO) [14] Senior notes: Ryan Ho Fluids and Nutrition.pdf (p9 — Enteral feeding indications)
Complications of Intussusception
Complications of intussusception can be organised into two broad categories: (A) complications of the disease itself (i.e., what happens if intussusception is not reduced in time, or progresses), and (B) complications of treatment (i.e., iatrogenic complications from enema reduction or surgery). Understanding these from first principles requires tracing the pathophysiological cascade back to the fundamental problem: mesenteric compression by the telescoped bowel.
A. Complications of the Disease (Untreated / Delayed Intussusception)
The natural history of untreated intussusception follows a predictable, stepwise progression driven by mesenteric vascular compromise:
Why it happens: The trapped mesentery between the intussusceptum and intussuscipiens undergoes progressive vascular compression. Veins (low-pressure, thin-walled) occlude first → venous congestion and oedema → if untreated, the swelling eventually compresses arteries (high-pressure, thick-walled) → arterial ischaemia → transmural necrosis (gangrene) [2][8].
Clinical features suggestive of strangulation [8]:
- Clinical signs: Fever, tachycardia, peritoneal signs (guarding, rigidity, rebound tenderness)
- Clinical symptoms: Continuous or worsening abdominal pain (loss of the classic pain-free intervals — the pain becomes constant because the ischaemia is now continuous, not just during peristaltic waves)
- Biochemical: Leucocytosis, metabolic acidosis, raised lactate → intestinal ischaemia [8]
- Radiological: Pneumatosis intestinalis (gas within the bowel wall from gas-producing bacteria infiltrating necrotic tissue), portal venous gas (gas entering mesenteric venous drainage and travelling to the portal system — an ominous sign), bowel wall thickening, reduced or lack of bowel wall enhancement on CT [8][15]
Significance: Morbidity and mortality are dependent on duration of ischaemia and its extent. Any length of ischaemic bowel can cause significant systemic effects secondary to sepsis and dehydration [8]. This is why early diagnosis and treatment are critical.
Prognosis of intestinal obstruction: Mortality 2% (non-strangulated) vs 10–30% (strangulated) [13].
Why it happens: Transmural necrosis weakens the bowel wall → the necrotic segment gives way → intestinal contents (faeces, bacteria, gas) spill into the peritoneal cavity.
Consequences:
- Faecal peritonitis: Spillage of enteric bacteria (E. coli, Bacteroides, Enterococcus) into the sterile peritoneal cavity triggers a massive inflammatory response → peritonitis [2].
- Pneumoperitoneum: Free gas visible under the diaphragm on erect CXR, or as Rigler's sign (both sides of bowel wall visible) on supine AXR [15].
- Septic shock: Bacterial contamination → systemic inflammatory response → multi-organ dysfunction.
Clinical features: Sudden worsening of pain (which may paradoxically briefly "improve" as the distended bowel decompresses on perforation — a false reassurance), followed by signs of generalised peritonitis (board-like rigidity, absent bowel sounds, fever, tachycardia, hypotension) [8].
Perforation = Absolute Contraindication to Enema Reduction
If perforation is suspected clinically or confirmed on erect CXR (pneumoperitoneum), do NOT attempt enema reduction — proceed directly to emergency laparotomy. Insufflation of air or fluid through perforated bowel would cause massive contamination of the peritoneal cavity or life-threatening tension pneumoperitoneum.
Why it happens: Follows from two mechanisms:
- Perforation → direct faecal contamination of peritoneum (see above).
- Bacterial translocation → even without frank perforation, the ischaemic, oedematous bowel wall loses its barrier function → bacteria and endotoxins translocate across the mucosa into the mesenteric lymphatics and portal circulation → bacteraemia and endotoxaemia [2].
Pathophysiology of sepsis from bowel ischaemia: Endotoxin (lipopolysaccharide from Gram-negative bacteria) triggers a cytokine cascade (TNF-α, IL-1, IL-6) → systemic vasodilation, capillary leak, myocardial depression → septic shock → multi-organ dysfunction (renal failure, DIC, ARDS).
Clinical features: High fever, tachycardia, hypotension, altered consciousness, poor capillary refill, oliguria. In infants, sepsis may present subtly with lethargy, poor feeding, and temperature instability (hypothermia as well as hyperthermia).
Why it happens: The intestinal obstruction component of intussusception causes fluid and electrolyte losses through multiple mechanisms [8]:
| Mechanism | Explanation |
|---|---|
| Vomiting | Proximal bowel dilatation → reverse peristalsis → loss of gastric acid (H⁺, Cl⁻), water, K⁺, Na⁺ |
| Reduced oral intake | Pain, nausea, and anorexia prevent the child from feeding |
| Third-space losses | Oedematous bowel wall transudates fluid into the bowel lumen and peritoneal cavity — this fluid is "sequestered" and functionally lost from the intravascular compartment |
| Defective intestinal absorption | The oedematous bowel wall cannot absorb luminal fluid normally |
Electrolyte consequences:
- Hypokalaemia: Loss of K⁺ in vomitus + metabolic alkalosis shifts K⁺ intracellularly + renal K⁺ wasting from RAAS activation (hypovolaemia → aldosterone → Na⁺ reabsorption and K⁺ secretion in collecting duct)
- Hypochloraemia: Loss of HCl in vomiting
- Metabolic alkalosis: Loss of H⁺ in vomiting (high SBO/gastric outlet pattern)
- Metabolic acidosis (late): If ischaemia develops → lactic acidosis overrides the alkalosis
- Hyponatraemia: Dilutional (from inappropriate ADH secretion in the setting of hypovolaemia) and loss in vomitus
Why it happens: If extensive bowel necrosis has occurred by the time of surgery, a large segment of bowel may need to be resected. In neonates and infants, the total small bowel length is shorter to begin with (~200–250 cm at birth), so losing even a moderate segment represents a proportionally larger loss.
Definition: Short bowel syndrome occurs when the remaining functional small bowel is insufficient to maintain adequate nutrient and fluid absorption (generally < 100 cm in children, or < 30 cm of jejunum + ileum if the ileocaecal valve is lost).
Consequences: Malabsorption, failure to thrive, dependence on parenteral nutrition, micronutrient deficiencies. Loss of the terminal ileum specifically impairs bile salt reabsorption (→ fat malabsorption, steatorrhoea) and vitamin B12 absorption.
Relevance to intussusception: This complication underscores the importance of early diagnosis and non-operative reduction — the longer the delay, the more bowel may need to be resected.
B. Complications of Treatment
| Complication | Incidence | Mechanism | Management |
|---|---|---|---|
| Bowel perforation | < 1% [2] | Excessive pressure on an already weakened, oedematous bowel wall causes it to rupture. Risk factors include age < 6 months, long duration of symptoms and higher pressure during reduction [2]. | Pneumatic reduction: perforation → tension pneumoperitoneum [4]. Immediate management: large-bore needle decompression (18G needle in RUQ subdiaphragmatic area to release trapped air), followed by emergency laparotomy, bowel resection, and washout. Hydrostatic reduction: perforation → fluid peritonitis. Immediate laparotomy required. Pneumatic technique is more advantageous if perforation occurs [2] — air is less irritating to the peritoneum than barium and tension pneumoperitoneum can be rapidly decompressed. |
| Recurrence | ~5% [4] | Possibility to develop recurrent intussusception due to residual bowel inflammation which may itself act as pathological lead point [2]. Most recurrences occur within 72 hours of reduction, though can occur weeks later. | First recurrence: repeat enema reduction is appropriate (success rate is similar). Second or third recurrence: strongly consider surgical exploration to rule out a pathological lead point (Meckel's diverticulum, polyp, lymphoma). |
| Incomplete reduction | Variable | The intussusception is partially but not completely reduced — a small residual "nubbin" of invagination may remain at the ileocaecal valve. | Re-attempt reduction. If persistent, surgical exploration. Some very small residual ileo-ileal intussusceptions may resolve spontaneously. |
| Post-reduction fever | Common | Patient usually presents with fever after successful reduction due to bacterial translocation or release of endotoxin or cytokines [2]. The ischaemic bowel wall allows passage of bacterial products into the bloodstream even after successful reduction. | Usually self-limiting (resolves within 24–48 hours). Monitor closely — persistent high fever may indicate incomplete reduction, perforation, or secondary infection. |
Tension Pneumoperitoneum — A Life-Threatening Emergency
If perforation occurs during pneumatic reduction, air escapes into the peritoneal cavity under pressure → tension pneumoperitoneum. This causes abdominal distension, splinting of the diaphragm, respiratory compromise, and cardiovascular collapse (compression of IVC → reduced venous return). Immediate needle decompression in the RUQ is required, followed by emergency laparotomy. This is why a surgeon must always be on standby during enema reduction.
| Complication | Mechanism | Prevention/Management |
|---|---|---|
| Wound infection | Contamination of the surgical wound by enteric organisms, especially if bowel was necrotic or perforated | Prophylactic IV antibiotics; meticulous wound care; delayed primary closure if heavily contaminated |
| Anastomotic leak | Following bowel resection with primary anastomosis, the join may fail to heal — especially if performed on oedematous, ischaemic, or poorly perfused bowel ends | Ensure well-vascularised, healthy bowel margins at anastomosis; tension-free suture; adequate nutrition post-operatively. Presents with fever, peritonitis, faecal drainage from wound/drain. Management: emergency re-laparotomy, washout, diversion (stoma). |
| Post-operative ileus | Normal post-operative temporary cessation of bowel motility due to handling of the bowel, anaesthesia, and inflammation | Expected and self-limiting (usually resolves in 2–5 days). NG decompression, IV fluids, NPO until bowel function returns (passage of flatus/stool). Prolonged ileus (> 5 days) warrants investigation for mechanical obstruction or intra-abdominal sepsis. |
| Adhesive small bowel obstruction | Intra-abdominal adhesions form as part of the healing process after any laparotomy → can cause SBO months to years later | This is a long-term risk of any abdominal surgery. Lifetime risk of adhesive SBO after childhood laparotomy is ~5–15%. Minimised by gentle tissue handling, avoiding unnecessary peritoneal disruption, and laparoscopic approach where possible. |
| Post-operative intussusception | Uncoordinated peristalsis during post-operative recovery can cause a new, usually ileo-ileal intussusception | Occurs in 1–5% of children after abdominal surgery (not specific to intussusception surgery). Usually ileo-ileal → not amenable to enema reduction → may require re-operation if does not resolve spontaneously. |
| Stoma-related complications (if stoma created) | If a stoma was necessary (e.g., in cases of severe peritonitis where primary anastomosis was unsafe): skin excoriation, prolapse, parastomal hernia, high-output stoma, electrolyte derangement | Specialist stoma nurse care; adequate fluid and electrolyte replacement; planned stoma reversal when patient recovered |
If a pathological lead point was the cause of intussusception, the complications of the lead point itself must be considered:
| Lead Point | Specific Complications |
|---|---|
| Meckel's diverticulum | GI bleeding (from ectopic gastric mucosa), Meckel's diverticulitis (mimics appendicitis), recurrent intussusception if not resected, Littre's hernia |
| Lymphoma (e.g., Burkitt) | If intussusception was the presenting feature of lymphoma, the child needs full oncological staging and treatment. Delay in diagnosis of the underlying malignancy is a significant risk. |
| Polyps (e.g., Peutz-Jeghers) | Recurrent intussusception if polyps are not removed. Peutz-Jeghers syndrome carries a lifetime cancer risk (GI, breast, pancreatic, ovarian) requiring surveillance. |
| HSP | Ongoing intestinal vasculitis, renal involvement (IgA nephropathy), recurrent intussusception if the bowel wall haematoma recurs |
| Scenario | Outcome |
|---|---|
| Early diagnosis + successful enema reduction | Excellent prognosis. Near-zero mortality. Full recovery within days. |
| Delayed presentation but reducible | Good prognosis if reduced before necrosis develops |
| Strangulated/necrotic bowel requiring resection | Mortality 10–30% (strangulated) [13]. Higher morbidity including risk of short bowel syndrome, anastomotic leak, prolonged hospitalisation |
| Recurrence | ~5% recurrence rate [4]. Most resolve with repeat enema reduction. Multiple recurrences warrant investigation for lead point. |
| Adult intussusception | Prognosis depends on the underlying aetiology — if malignant, depends on stage and histology |
High Yield Summary
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Complications of the disease itself follow the cascade: venous congestion → oedema → arterial ischaemia → necrosis → perforation → peritonitis → sepsis → multi-organ failure and death.
-
Strangulation is the most feared complication. Clinical features: constant pain (loss of pain-free intervals), fever, tachycardia, peritoneal signs, leucocytosis, raised lactate / metabolic acidosis [8]. Radiological signs: pneumatosis intestinalis, portal venous gas, lack of bowel wall enhancement [8][15].
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Perforation during enema reduction occurs in < 1% of cases [2]. Risk factors: age < 6 months, long duration of symptoms, high pressure during reduction [2]. If pneumatic → tension pneumoperitoneum requiring needle decompression then laparotomy [4].
-
Recurrence rate ~5% [4] — usually due to residual bowel inflammation acting as lead point [2]. First recurrence: repeat enema. Multiple: investigate for pathological lead point.
-
Post-reduction fever is expected — due to bacterial translocation / endotoxin release from previously ischaemic bowel [2]. Self-limiting; persistent fever warrants investigation.
-
Surgical complications: wound infection, anastomotic leak, post-operative ileus, adhesive SBO (long-term), post-operative intussusception (ileo-ileal).
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Mortality: 2% non-strangulated vs 10–30% strangulated intestinal obstruction [13]. Early diagnosis and reduction are key to minimising morbidity and mortality.
Active Recall - Complications of Intussusception
References
[2] Senior notes: felixlai.md (Intussusception — Treatment, Complications, Pathogenesis sections) [4] Senior notes: maxim.md (Intussusception table — Complications: bowel perforation, tension pneumoperitoneum, recurrence 5%) [5] Senior notes: Ryan Ho GI.pdf (p134) [8] Senior notes: felixlai.md (Complications of intestinal obstruction — Strangulation section) [13] Senior notes: Ryan Ho GI.pdf (p137–139 — Complications of IO, strangulation signs, prognosis) [15] Senior notes: felixlai.md (CT findings of complicated IO — pneumatosis intestinalis, portal venous gas, bowel wall changes)
Intestinal Obstruction
Intestinal obstruction is a partial or complete blockage of the small or large bowel that prevents the normal passage of intestinal contents, leading to proximal dilation, fluid accumulation, and potential ischemia.
Peritonitis
Peritonitis is inflammation of the peritoneum, typically caused by bacterial infection due to perforation of an abdominal viscus or contamination of the peritoneal cavity, presenting with severe abdominal pain, rigidity, and systemic sepsis.