GC016 Radiology Of Common Medical And Surgical Problems
Radiology of common medical and surgical problems encompasses the use of imaging modalities such as X-ray, ultrasound, CT, and MRI to diagnose, evaluate, and guide management of frequently encountered clinical conditions across medical and surgical disciplines.
Radiology of Common Medical and Surgical Problems
This lecture, delivered by Dr Elaine Lee (Clinical Associate Professor, HKU Radiology), is a case-based review that walks you through common medical and surgical conditions — pancreatitis, lobar collapse/lung mass, appendicitis, and intussusception — to teach you when and why to choose a particular imaging modality, what findings to look for, and how to interpret those findings in the clinical context. The overarching principle is that imaging should always be guided by clinical reasoning: you form a working diagnosis first, then select the modality that best answers your clinical question in the clearest, fastest, safest, and cheapest way [1][2].
Learning Objectives (from slide 2):
Review of imaging features of common medical and surgical conditions [1]
Revisit the approach to imaging; selection of most appropriate imaging modality [1]
How it fits into exams: This lecture is a perennial favourite for both MCQ and SAQ questions. Past papers have directly examined appendicitis imaging (2016 Q9), pancreatitis investigations (2019 Q5), AAA imaging (2017 Q6), and modality selection principles (2021 Q1, Q81, Q82). Expect a clinical vignette → "what is the diagnosis?" → "what imaging?" → "what do you see?" → "what are the complications?"
Before diving into cases, understand why each modality exists and when it is best suited:
| Modality | Physics | Best For | Pros | Cons |
|---|---|---|---|---|
| Plain X-ray | 2D projection using X-rays | Bones, lung fields, bowel gas pattern, free air | Cheap, fast, universally available | Limited soft-tissue contrast, 2D superimposition, radiation |
| Ultrasound (USG) | Sound waves reflected by tissue interfaces | Superficial structures, paediatrics, gallbladder, appendix, obstetrics, breast | No radiation, cheap, real-time, portable | Operator-dependent, limited by body habitus/gas, poor penetration |
| CT | Cross-sectional X-ray with computer reconstruction | Bones + soft tissue, vascular (with contrast), abdominal emergencies | Excellent anatomical detail, fast, less operator-dependent, 3D reconstruction | Radiation, cost, contrast risk (nephrotoxicity, allergy) |
| MRI | Magnetic fields and radiofrequency pulses | Soft tissues (brain, spine, joints, pelvis), staging | Best soft-tissue contrast, no radiation | Expensive, slow, limited availability, CI in pacemakers/metallic implants |
| Nuclear Medicine / PET-CT | Radioactive tracers showing metabolic activity | Functional imaging (thyroid, bone mets, cancer staging) | Very sensitive for metabolic activity | Poor anatomical detail alone, radiation, expensive |
"The best modality is the one which can answer the clinical question in the clearest, fastest, safest and cheapest way." [2]
Exam Principle — Modality Selection
When a question asks "what is the most appropriate imaging investigation?", think: (1) What am I trying to answer? (2) What is the patient population (child → USG preferred to avoid radiation; pregnant → avoid radiation)? (3) Is there a contraindication to contrast (eGFR < 30 → avoid CT contrast, use V/Q scan for PE instead)? [3]
Case 1: Acute Pancreatitis
A 55-year-old man was admitted with severe upper abdominal pain and nausea. He had a history of alcohol abuse. O/E the epigastrium was tender with guarding. [1]
Acute pancreatitis [1]
Why? The triad of (1) severe epigastric pain (often radiating to the back), (2) history of alcohol abuse (one of the two most common aetiologies alongside gallstones), and (3) epigastric tenderness with guarding is classic.
Serum amylase/lipase [1]
- Amylase ≥ 3× upper limit of normal is diagnostic. However, amylase can be normal in chronic pancreatitis (burned-out gland) or late presentation.
- Lipase is more sensitive and specific and stays elevated longer.
- Why these first? Because pancreatitis is fundamentally a clinical + biochemical diagnosis — imaging is NOT needed to make the initial diagnosis if symptoms and enzymes are concordant.
Inflammation of the pancreatic tissue → obstruction of small pancreatic ducts → leak of pancreatic juices to surrounding tissues → swollen oedematous pancreas with areas of haemorrhage and necrosis → peripancreatic fluid collection [1]
First-principles explanation: The pancreas produces powerful proteolytic enzymes (trypsin, elastase, phospholipase A2) that are normally activated only in the duodenum. In pancreatitis, premature intracellular activation of trypsinogen to trypsin triggers autodigestion. The inflammatory cascade causes:
- Oedema → the gland swells (interstitial oedematous pancreatitis)
- Necrosis → if blood supply is compromised or inflammation is severe, portions of parenchyma die (necrotizing pancreatitis)
- Peripancreatic fluid → enzyme-rich juice leaks into the retroperitoneal space and lesser sac
- Systemic response → cytokine storm can cause SIRS, organ failure
Interstitial oedematous vs. Necrotizing pancreatitis [1]
| Feature | Interstitial Oedematous | Necrotizing |
|---|---|---|
| CT enhancement | Pancreas enhances uniformly | Non-enhancing areas = necrosis |
| Fluid collections | Acute peripancreatic fluid collections (APFC) | Acute necrotic collections (ANC) |
| Late evolution | Pseudocyst (walled-off by fibrous capsule) | Walled-off necrosis (WON) |
| Prognosis | Usually self-limiting | Higher morbidity/mortality (infection of necrosis is key complication) |
Role of imaging:
- Confirm diagnosis if symptoms are atypical or serum amylase/lipase levels are less than expected
- Determine the cause of pancreatitis; exclude neoplasm or confirm presence of cholelithiasis
- Patient's condition does not improve (disease severity)
- Monitor evolution and complications [1]
This is extremely high-yield. The exam loves asking "when do you order a CT in pancreatitis?" The answer is NOT on Day 1 for a straightforward clinical presentation. CT is best performed 72–96 hours after symptom onset because necrosis takes time to evolve and may not be visible earlier.
Extrapancreatic spread of inflammation — fluid collection, obliteration of peripancreatic soft tissue & fascial thickening. Look for necrosis — non-enhancement (necrotising pancreatitis) with acute necrotic collections (ANC). [1]
Other complications: Walled off necrosis (WON), ascites, mesenteric involvement [1]
How to read the CT:
- Normal pancreas enhances homogeneously with IV contrast
- Non-enhancing areas ( > 30% of the gland) indicate significant necrosis
- Peripancreatic fat stranding = inflammation extending beyond the gland
- Fluid collections in the lesser sac, anterior pararenal space, paracolic gutters
High Yield — Pancreatitis Imaging Timeline
Do NOT routinely order CT on Day 1 of acute pancreatitis. CT is indicated when: (1) diagnosis is uncertain, (2) clinical deterioration (fever, rising WCC, organ failure), (3) to assess severity/complications after 72–96 hours. The reason is that necrosis may not be apparent on early CT, leading to underestimation of severity.
- 2019 SAQ Q5: 55-year-old lady, epigastric pain, amylase 1250 → Diagnosis = acute pancreatitis. Investigations to guide management = USS abdomen (gallstones?), CT abdomen (if deteriorating/complications), FBC, CRP, Ca²⁺, glucose, LDH (severity scoring). Common causes = gallstones, alcohol, idiopathic [4].
Case 2: Lobar Collapse / Lung Mass
A 44-year-old lady was referred to the OP department after a routine PA CXR showed an abnormality. She never smoked in her life but was treated for TB 10 years previously. [1]
Haziness in left lung → specifically LUL (left upper lobe) collapse [1]
Hazy or veil-like appearance "Tented" left hemidiaphragm Increase retrosternal density on lateral CXR Look for proximal obstructing lesion [1]
Why does this happen? When the LUL bronchus is obstructed, air distal to the obstruction is reabsorbed by the blood → the lobe deflates → it loses volume → surrounding structures shift toward the collapsed lobe:
- Elevated hemidiaphragm (or "tented")
- Mediastinal shift toward the side of collapse
- The collapsed lobe appears as a veil-like opacity because it is now a thin sheet of airless tissue draped over the mediastinum
A contrast CT scan of the thorax was performed. Bronchoscopy showed narrowing of the LUL bronchus without endobronchial lesion. BAL and sputum analysis revealed no cells or growth. TB culture was pending. [1]
CT: LUL collapse with narrowed LUL bronchus. No mediastinal masses or nodes. Rest of lungs are normal. [1]
LUL collapse secondary to TB stricture [1]
TB can cause bronchial stenosis through:
- Endobronchial TB → granulomatous inflammation of bronchial wall
- Healing with fibrosis → cicatricial stricture
- Extrinsic compression by calcified lymph nodes (less common)
In adults, lobar collapse on CXR should be [investigated] to exclude neoplastic lesion [1]
RUL collapse — Golden S-sign [1]
High Yield — Golden S-Sign
The Golden S-sign (also called the reverse S-sign of Golden) is seen with RUL collapse when a hilar mass causes the collapse. The lateral part of the minor fissure is elevated (due to volume loss), while the medial part is pushed down by the mass, creating an "S" or reverse "S" shape. This sign strongly suggests a central bronchogenic carcinoma causing the obstruction. Always think cancer in adult lobar collapse until proven otherwise!
| Lobe | CXR Signs | Key Associations |
|---|---|---|
| RUL | Golden S-sign, elevated minor fissure, tracheal deviation to right | Central bronchogenic carcinoma |
| RML | Loss of right heart border (silhouette sign), triangular opacity on lateral | RML syndrome (recurrent infection) |
| RLL | Triangular opacity behind heart, depressed right hilum, loss of right hemidiaphragm silhouette | Mucus plugging, post-op |
| LUL | Veil-like opacity, tented hemidiaphragm, increased retrosternal density on lateral | TB stricture, bronchogenic carcinoma |
| LLL | Triangular opacity behind heart, depressed left hilum, loss of left hemidiaphragm | Mucus plugging, post-op |
- 2016 SAQ Q5: 60-year-old man with mass in left upper zone → lung malignancy with hypercalcaemia (SCC → PTHrP), raised ALP (bone mets), raised creatinine (myeloma vs renal impairment) [5].
- 2021 MCQ Q82: CXR with bilateral perihilar consolidation, blunted costophrenic angles, cardiomegaly, Kerley B lines, upper lobe venous diversion → heart failure (not pneumonia or metastatic disease) [6].
Case 3: Acute Appendicitis
A 25-year-old law student was admitted with a few days of right lower abdominal pain. She was nauseous and feverish. O/E tender RLQ with guarding and febrile. [1]
Appendicitis [1]
Faecolith or scarring that occludes neck of appendix → closed-loop obstruction → bacterial infection and ulceration of wall which perforates → abscess formation or generalised peritonitis [1]
Most frequent condition requiring emergency surgery (80%). Produced by luminal obstruction, secondary distention, engorgement, edema and bacterial overgrowth. Peak frequency in children: 12–15 years of age. [1]
First-principles explanation: The appendix is a blind-ended tube. When the lumen is obstructed (by faecolith, lymphoid hyperplasia in children, rarely neoplasm in elderly), the mucosa continues to secrete mucus → intraluminal pressure rises → venous drainage is impaired → wall becomes ischaemic → bacteria translocate → inflammation (appendicitis). If untreated, the wall becomes gangrenous and perforates → either localized abscess (if omentum walls it off) or generalized peritonitis.
USG showed thickened appendix and normal right ovary [1]
Why USG first? In a young female patient, you also need to exclude ovarian pathology (torsion, ruptured cyst, ectopic pregnancy). USG is:
- No radiation (important in young/female of reproductive age)
- Can visualize both appendix and ovaries
- Real-time and can assess for graded-compression tenderness
Graded-compression technique Focal tenderness Lack of compressibility Transverse diameter ≥ 6mm Appendicolith Peri-caecal or peri-appendiceal fluid [1]
| USG Feature | Explanation |
|---|---|
| Graded compression | The transducer is pressed firmly over the RLQ to displace bowel gas; a normal appendix compresses flat, an inflamed one does not |
| Non-compressible | The wall is rigid due to oedema and inflammation |
| Diameter ≥ 6mm | Normal appendix is < 6mm outer wall-to-wall. An enlarged diameter indicates distension from obstruction |
| Appendicolith | A calcified faecolith causing the obstruction; appears as an echogenic focus with posterior acoustic shadowing |
| Periappendiceal fluid | Free fluid around the appendix indicates inflammation or microperforation |
| Increased colour Doppler flow | Hyperaemia of the wall (slide 35) indicates inflammation |
Appendix may be difficult to identify, mucosa disrupted. Phlegmon: inflammatory mass [1]
Why is the appendix hard to see after perforation? Because the wall has lost its integrity and the appendix "dissolves" into the surrounding inflammatory mass (phlegmon). The phlegmon is a mass of inflamed omentum, bowel loops, and mesentery walling off the perforation.
CT Advantages:
- Less operator dependent
- Higher sensitivity than US
- Pooled sensitivity 94% (US 88%)
- Pooled specificity 95% (US 94%)
- Indications: Obese patients, delineate disease extent in perforated appendicitis, guide abscess drainage
- Non-visualisation of the appendix on CT has a high negative predictive value of 98.7% [1]
High Yield — USG vs CT for Appendicitis
USG is first-line, especially in children, young women, and thin patients. CT is used when: (1) USG is inconclusive, (2) patient is obese (ultrasound cannot penetrate), (3) perforation is suspected and you need to delineate the extent, (4) abscess drainage guidance is needed. Key stat: If CT does not show the appendix, the NPV is 98.7% — you can essentially rule out appendicitis.
- 2016 SAQ Q9: 7-year-old boy, fever, RLQ tenderness → (a) Appendicitis; (b) USG — reasons: no radiation (child), can assess appendix and exclude other causes, can show specific signs (thickened appendix, non-compressible, ≥ 6mm); (c) Thickened non-compressible appendix ≥ 6mm, appendicolith, periappendiceal fluid; (d) CT — especially useful in obese child [5].
Case 4: Intussusception
An 18-month-old baby girl was admitted with 1 day history of crying and being off her food. Her mother described episodes where she draws up her legs and cries. [1]
Dilated small bowel. A "tumour" or intussusceptum in the RUQ [1]
Classic clinical triad: acute abdominal colic, currant-jelly stools, a palpable abdominal mass (present in less than 50% of patients). Age: 6 months – 2 years. Mostly ileo-colic. [1]
Exam Trap — Classic Triad
The complete triad of abdominal colic + currant-jelly stool + palpable mass is present in less than 50% of patients. Do NOT wait for the full triad before suspecting intussusception. A child in the right age group with episodic crying, drawing up legs, and vomiting is enough to warrant USG.
Invagination or prolapse of a segment of bowel (intussusceptum) into the lumen of adjacent bowel (intussuscipiens) due to peristalsis. Major cause of SBO in children, less common in adults. In adults, 80% cases are due to polypoid tumour. Children — commonly near the ileocaecal valve. [1]
Why the ileocaecal region? The ileocaecal valve is a natural anatomical transition point where the narrow ileum meets the wider caecum. Enlarged Peyer's patches (from viral illness, e.g., adenovirus, rotavirus) act as a lead point, and normal peristalsis telescopes the ileum into the caecum.
Why currant-jelly stools? As the bowel is telescoped, the mesenteric vessels are compressed → venous congestion → mucosal ischaemia → bloody mucus mixed with stool = "currant jelly" appearance. This is a late sign indicating significant vascular compromise.
USG: Primary imaging modality for initial diagnosis. Sensitivity: 98–100%, Negative predictive value: 100%, Specificity: 88–100%, Alternative diagnosis. [1]
Why USG?
- No radiation in a paediatric patient
- Essentially perfect sensitivity (98–100%) → if you don't see it on USG, it's not there
- Can identify the classic signs AND can be used to guide therapeutic reduction
The target/doughnut sign (transverse view) and pseudokidney sign (longitudinal view):
Three-ring structure:
- Central ring: lumen and wall of intussusceptum
- Middle ring: mesenteric fat
- Outer ring: bowel wall of intussusceptum and intussuscipiens [1]
| Sign | View | Appearance | Explanation |
|---|---|---|---|
| Doughnut / Target sign | Transverse | Concentric rings | Cross-section through the telescoped bowel shows alternating layers of wall, mesentery, and wall |
| Pseudokidney sign | Longitudinal | Kidney-shaped mass | The hyperechoic mesenteric fat (like renal sinus) is surrounded by hypoechoic bowel wall (like renal cortex) |
The intussusception was reduced with water under ultrasound control [1]
Post-reduction — fluid filled bowel [1]
How does this work? Under USG (or fluoroscopic) guidance, liquid (water/saline) or air is introduced per rectum. The hydrostatic or pneumatic pressure pushes the intussusceptum back out of the intussuscipiens. This is a non-surgical therapeutic procedure with success rates of ~80–95%.
Contraindications to enema reduction:
- Peritonitis (perforation)
- Free intraperitoneal air
- Hemodynamic instability / shock
- Signs of bowel necrosis
In these cases → surgical reduction (manual or resection if gangrenous bowel).
| Feature | Children | Adults |
|---|---|---|
| Most common type | Ileocolic | Small bowel–small bowel |
| Lead point | Usually none (idiopathic; enlarged Peyer's patches) | 80% have a pathological lead point (polyp, tumour, Meckel's diverticulum) |
| Management | Non-operative reduction (enema) first | Surgery (because of high likelihood of tumour) |
| Age | 6 months – 2 years | Any age |
This table synthesizes the lecture's approach across all four cases and integrates commonly tested scenarios from supporting GC material:
| Condition | First-Line Imaging | Why | When to Escalate to CT/MRI |
|---|---|---|---|
| Acute pancreatitis | Usually clinical + amylase/lipase; USG for aetiology (gallstones) | Diagnosis is biochemical; USG checks for gallstones | CT if deteriorating, complications suspected, or diagnosis uncertain (after 72–96h) |
| Lobar collapse (adult) | PA CXR | Screening, readily available | Contrast CT thorax to exclude bronchogenic carcinoma; bronchoscopy |
| Appendicitis | USG (graded compression) | No radiation, assesses appendix + ovary in females | CT if USG inconclusive, obese patient, or to delineate complicated/perforated disease |
| Intussusception (child) | USG | No radiation, near-perfect sensitivity | CT rarely needed; if diagnosis is clear, proceed to therapeutic enema under USG/fluoroscopy |
| Gallstones / cholecystitis | USG | Gallbladder is superficial, excellent for stones | CT/MRCP if CBD stones suspected or complications |
| Bowel obstruction | AXR (supine ± erect) | Shows dilated loops, air-fluid levels, transition point | CT for cause and complications |
| Pneumoperitoneum | Erect CXR | Free gas under diaphragm (Rigler's sign on AXR) | CT if CXR negative but clinical suspicion high |
| Aortic dissection | CXR (widened mediastinum) → CT aortogram | CXR screening; CT is diagnostic gold standard | CTA with pre- and post-contrast |
| PE | CTPA | High sensitivity and specificity | V/Q scan if eGFR < 30 or contrast allergy; DVT Doppler if pregnant |
| Breast lump | USG (< 35y) or mammogram (≥ 35y) | Age-dependent breast density affects mammogram sensitivity | MRI for staging, high-risk screening |
| Pelvic mass | Pelvic USG | First-line, no radiation, excellent for uterine/ovarian pathology | MRI for characterisation and staging |
Additional High-Yield Points from Supporting GC Material
When reading any CXR, use the ABCDE approach:
- A — Airway: tracheal deviation, main bronchi
- B — Bones: ribs, clavicles, scapulae, spine (fractures, lytic lesions)
- C — Cardiac: heart size (CT ratio < 0.5 on PA film), mediastinal contour
- D — Diaphragm: costophrenic angles blunted (effusion), free air under diaphragm
- E — Everything else: lung fields (consolidation, masses, collapse), soft tissues, lines/tubes
Bilateral perihilar consolidation, blunting of costophrenic angles, cardiomegaly, Kerley B lines, upper lobe venous diversion → Heart failure [6]
Mnemonic: ABCDE of heart failure CXR:
- A — Alveolar oedema (bat-wing pattern)
- B — Kerley B lines (interstitial oedema, interlobular septal thickening)
- C — Cardiomegaly (CT ratio > 0.5)
- D — Upper lobe Diversion (cephalization of vessels)
- E — Pleural Effusion (blunted costophrenic angles)
Percutaneous transhepatic biliary drainage (PTBD) for malignant biliary obstruction, abscess drainage (e.g., appendix abscess), embolization for bleeding [8]
From 2021 MCQ Q2: 50-year-old man with painless jaundice, pruritus, weight loss, pancreatic head mass on USG → PTBD to relieve biliary obstruction [6].
| Trap | Correct Reasoning |
|---|---|
| Ordering CT on Day 1 of pancreatitis | CT is not routine on Day 1; biochemical diagnosis first; CT at 72–96h if deteriorating |
| Choosing CT over USG for paediatric appendicitis | USG is first-line in children (no radiation); CT only if USG inconclusive or child is obese |
| Confusing lobar collapse with pleural effusion | Collapse: structures shift toward the opacity. Effusion: structures shift away from the opacity (or no shift if small) |
| Missing the Golden S-sign as a sign of malignancy | Golden S-sign on RUL collapse = central bronchogenic carcinoma until proven otherwise |
| Assuming intussusception triad is always present | Classic triad present in < 50%; do not delay imaging |
| Choosing MRI as first-line for acute abdomen | MRI is slow and expensive; CT or USG is preferred for acute surgical conditions |
| Non-visualization of appendix on CT = inconclusive | Non-visualization on CT has NPV of 98.7% → essentially rules out appendicitis |
Past-Paper Style Stems and Markscheme Points
Q1. A 55-year-old man with alcohol abuse presents with severe epigastric pain. Amylase is 1500 U/L. When is CT abdomen indicated?
- Answer: CT is NOT needed for initial diagnosis (clinical + biochemical). Indicated when: (1) diagnosis uncertain / atypical presentation, (2) clinical deterioration (fever, organ failure), (3) assess severity and complications (necrosis, abscess, WON), (4) guide intervention (e.g., drainage). Best performed ≥ 72–96 hours from onset.
Q2. Name 4 CT findings of necrotizing pancreatitis.
- Answer: (1) Non-enhancing areas of pancreatic parenchyma (necrosis), (2) peripancreatic fluid collections / ANC, (3) obliteration of peripancreatic fat planes / fascial thickening, (4) mesenteric involvement / ascites. Late: WON with wall enhancing around necrotic collection.
Q3. What CXR signs suggest LUL collapse? What must be excluded in adults?
- Answer: Veil-like/hazy opacity in left upper zone, "tented" left hemidiaphragm, increased retrosternal density on lateral CXR, ± mediastinal shift to left. Must exclude: bronchogenic carcinoma (CT thorax + bronchoscopy).
Q4. A 7-year-old boy presents with RLQ pain and fever. Name the most appropriate imaging and 3 reasons.
- Answer: USG. Reasons: (1) No ionizing radiation (important in child), (2) Can directly visualize appendix (non-compressible, ≥ 6mm), (3) Can exclude other diagnoses (mesenteric adenitis, ovarian pathology in girls), (4) Can detect complications (perforation, abscess).
Q5. Describe 3 USG criteria for diagnosing appendicitis.
- Answer: (1) Non-compressible appendix, (2) transverse diameter ≥ 6mm, (3) appendicolith, (4) periappendiceal/pericaecal fluid, (5) increased colour Doppler flow, (6) focal tenderness at probe site.
Q6. An 18-month-old presents with episodic crying and draws up legs. Describe the imaging approach.
- Answer: USG abdomen (first-line). Look for target/doughnut sign (transverse) and pseudokidney sign (longitudinal). Sensitivity 98–100%. If confirmed and no contraindications (perforation, peritonitis, shock), proceed to hydrostatic/pneumatic reduction under USG or fluoroscopic guidance.
Q7. Why is CT preferred over USG in an obese patient with suspected appendicitis?
- Answer: USG has limited penetration in obese patients due to subcutaneous fat attenuating the ultrasound beam. CT is less operator-dependent and has higher pooled sensitivity (94% vs 88%) and specificity (95% vs 94%). CT can also better delineate the extent of disease in perforation and guide abscess drainage.
High Yield Summary
1. Pancreatitis: Diagnosis is clinical + amylase/lipase. CT at 72–96h if deteriorating → look for non-enhancing necrosis, peripancreatic fluid, ANC. Late complications: WON, abscess, mesenteric involvement.
2. Lobar Collapse: In adults, ALWAYS exclude malignancy. Know the CXR signs for each lobe (especially Golden S-sign for RUL). Follow up with contrast CT + bronchoscopy.
3. Appendicitis: USG first (especially children/young females) — non-compressible, ≥ 6mm, appendicolith, periappendiceal fluid. CT if inconclusive/obese/complicated. Non-visualization on CT → NPV 98.7%.
4. Intussusception: Classic triad present < 50%. USG sensitivity 98–100% → target sign, pseudokidney sign. Therapeutic reduction with hydrostatic/pneumatic enema. In adults, suspect tumour as lead point.
5. Modality Selection Principle: Answer the clinical question in the clearest, fastest, safest, and cheapest way. USG for paediatrics/superficial/no radiation. CT for complex/obese/acute surgical. MRI for soft tissue/staging.
Active Recall - Radiology of Common Medical and Surgical Problems
[1] Lecture slides: GC 016. Radiology of Common Medical and Surgical Problems.pdf (slides 1–49) [2] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p5 — imaging modalities table and selection principle) [3] Senior notes: Block A - Chest Pain - Department of Radiology.pdf (CXR approach, aortic dissection, CTPA) [4] Past papers: 2019 Fourth Summative SAQ.pdf (Q5 — pancreatitis) [5] Past papers: 2016 Fourth Summative SAQ.pdf (Q5 — lung mass with biochemical abnormalities; Q9 — appendicitis imaging in a child) [6] Past papers: 2021 Fourth Summative Assessment MCQ.pdf (Q1 — mammogram; Q2 — PTBD; Q82 — heart failure CXR) [7] Lecture slides: GC 013. Emergency radiology.pdf (learning objectives — approach to emergencies and modality selection) [8] Lecture slides: IR 2025_VLau.pdf (interventional radiology scope and principles)
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