Lower Gi Bleed
Lower gastrointestinal bleeding is hemorrhage originating distal to the ligament of Treitz, most commonly from colonic sources such as diverticulosis, angiodysplasia, or colorectal neoplasms.
History Taking: Lower GI Bleed (LGIB)
This is the one complaint where you might need to resuscitate before you history-take. A patient passing large-volume bright red blood per rectum can be in hypovolaemic shock. Your first job is a quick "eyeball" assessment. [1][2]
- Is the patient haemodynamically stable? (BP, pulse, conscious level, capillary refill)
- Very severe: hypotension, tachycardia, agitation, confusion, drowsiness, coma [2]
- Moderate to severe: postural hypotension (indicates ≥20% reduction in blood volume) [2]
In your OSCE, you won't literally resuscitate the mannequin, but you should verbalise that you would assess haemodynamic stability first. This scores marks.
Cantonese phrasing:
- "你而家覺得頭暈嗎？企起身會唔會暈？" (Do you feel dizzy? Dizzy when standing up?)
- "你隻手腳有冇凍？" (Are your hands and feet cold?)
1. Characterise the Bleeding
This is the most important part of your history. The way blood appears tells you roughly where it comes from. [1][2][3]
| Finding | Likely Source | Cantonese |
|---|---|---|
| Blood mixed with faeces | Proximal to sigmoid (right colon) — faeces still fluid so blood mixes in [1][2] | 血同大便撈埋一齊 |
| Blood on surface of stools / streaking | Left colon / rectum — faeces already solid [1] | 血喺大便外面 |
| Blood on toilet paper only | Anorectal conditions — mild, close to anal margin [1][2] | 抹嘅時候先見到血 |
| Blood after defecation | Anus, e.g. haemorrhoids [2] | 屙完之後先滴血 |
| Blood by itself (torrential) | Diverticular disease, angiodysplasia, rectal varices [2] | 淨係出血，冇大便 |
| Melena (黑色、臭、稀) | Upper GI or right colon [2] | 大便黑色好似芝麻糊，好臭 |
Practical phrasing:
- "你見到嘅血係咩顏色？鮮紅色定暗紅色定黑色？" (What colour is the blood? Bright red, dark red, or black?)
- "血係混喺大便入面，定喺大便外面，定抹嘅時候先見到？" (Is the blood mixed in the stool, on the surface, or only on wiping?)
- "有冇試過淨係出血冇大便？" (Have you ever passed blood by itself without stool?)
Why the relationship of blood to stool matters
This single question narrows your differential enormously. Blood mixed with stool = proximal source (cancer, IBD, diverticular disease). Blood separate from stool = outlet-type (haemorrhoids, fissure). Blood by itself in large volume = vascular cause (diverticular, angiodysplasia). Examiners love this distinction. [1][2]
- "每次出幾多血？好似幾多？有冇成廁所都係血？" (How much blood each time? Has the toilet bowl been full of blood?)
- "出咗幾多次？幾時開始？" (How many times? When did it start?)
- "係持續出血定間歇性？" (Continuous or intermittent?)
Why this matters: Diverticular bleeding is classically painless, profuse haematochezia that stops spontaneously in 80–85% of cases but can be massive. [1][2] Angiodysplasia tends to be intermittent and less severe (venous bleeding). [1][2] Colorectal cancer tends to be low-grade, intermittent and may present with iron-deficiency anaemia rather than frank haematochezia. [4]
2. Associated GI Symptoms
- "你大便習慣有冇改變？有冇試過肚屙同便秘輪住嚟？" (Any change in bowel habits? Alternating diarrhoea and constipation?)
- "有冇痾黏液？" (Any mucus in stools?)
- "大便嘅粗幼有冇變？" (Has the calibre of your stool changed?)
- Why: Change in stool calibre is a red flag for obstructing colorectal lesion. [3]
- "肛門有冇痛？痕？有冇嘢突出嚟？" (Any pain/itchiness at the anus? Any lump coming out?)
- Perianal mass/pain → haemorrhoids (especially if thrombosed), perianal abscess [3]
- Pruritus → haemorrhoids (mucus secretion), threadworms
- Sense of prolapse → haemorrhoids
- "有冇嘔血？嘔啡色嘢？" (Any vomiting blood? Coffee-ground vomitus?)
- Why: 10–15% of haematochezia is actually from a massive upper GI bleed. Always consider this, especially if the patient is haemodynamically unstable. [2]
These are the questions examiners specifically look for. [3][5]
- Change in bowel habit (alternating diarrhoea/constipation) [3][5]
- Tenesmus [3][5]
- Mucus per rectum [3][5]
- Duration of bleeding [5]
- Blood mixed with stool [5]
- Melaena / altered blood / dark red / maroon-coloured [5]
- Older age (>50) [5]
- Constitutional symptoms: weight loss (體重有冇輕咗?), loss of appetite (冇胃口?), fatigue (成日好攰?) [2][3]
- Family history of colorectal cancer or polyposis syndromes [3][5]
- Symptoms of metastatic spread: jaundice (skin/eyes yellow), bone pain, persistent cough/SOB, intractable sacral pain [2]
Red Flag Checklist for PR Bleeding
If a patient is >50 years old with any change in bowel habit, weight loss, blood mixed with stool, or family history of CRC — this is a two-week-wait referral for colonoscopy. Students commonly forget to ask about family history and constitutional symptoms. Don't lose these easy marks. [5]
This is where you earn extra marks — showing the examiner you're thinking about specific diagnoses. [1][2][3]
| Differential | Key Differentiating Questions | Why It Matters |
|---|---|---|
| Diverticular disease (憩室病) | Painless profuse haematochezia? Self-limiting? Previous episodes? [1][2][3] | Commonest cause of LGIB (17–40%). Painless. Stops spontaneously 80–85%. Right-sided diverticula commoner in Asians. [1] |
| Angiodysplasia | Elderly? Hx of aortic stenosis? Hereditary haemorrhagic telangiectasia? CKD? [1][2] | Degenerative, venous bleeding, intermittent. Associations: Heyde syndrome (aortic stenosis), Osler-Weber-Rendu. [1][2] |
| Colorectal carcinoma | >50y? Change in bowel habit? Pencil-thin stools? Tenesmus? Weight loss? FHx? Smoker? Previous polyps? [2][3] | ~10% of PR bleed in >50y. Low-grade, intermittent bleeding. May present as iron-deficiency anaemia. [4] |
| IBD | Young patient? Bloody diarrhoea? Mucus? Extra-intestinal features (joint pain, skin rash, eye symptoms)? [2] | UC more commonly causes bleeding than Crohn's. Ask about extra-intestinal manifestations. [4] |
| Ischaemic colitis | CVS risk factors? Acute MI? Stroke? AF? Abdominal pain post-prandially? [2] | Classically LIF pain with bloody diarrhoea in elderly with vascular risk factors. |
| Infective colitis | Fever? Recent travel (TOCC)? Antibiotics (C. difficile)? Food history? Contacts? Immunosuppression (CMV)? [2][6] | Must exclude infectious causes before diagnosing IBD. |
| Haemorrhoids | Outlet-type bleeding? Blood on wiping/dripping after defecation? Constipation? Pregnancy? Perianal lump? [1][2][3] | Most common cause of LGIB in < 50y. Painless unless thrombosed. |
| Anal fissure | Severe sharp pain on defecation? Hx of constipation? [2] | Classic triad: pain, spasm, bleeding on defecation. |
| Radiation proctocolitis | Previous pelvic RT (cervical, prostate, rectal cancer)? Timing of symptoms relative to RT? [1][4] | Acute (< 6 weeks) or delayed ( > 9 months, can be >10 years). [4] |
| Post-polypectomy | Recent colonoscopy or polypectomy? [1][5] | Acute (arterial) or delayed (eschar slough) bleeding. Always ask! [1] |
| Meckel's diverticulum | Young patient? Painless bleeding? [1] | Rule of 2s. Important in paediatric/young adult LGIB. |
| Rectal varices | Known liver disease? Portal hypertension? [4] | Portosystemic shunt between superior and inferior rectal veins. Severe bleeding. [4] |
| GI endometriosis | Cyclical bleeding pattern? Young female? [3] | Bleeding in a cyclical manner → pathognomonic. [3] |
5. Targeted Systems Review
- AF, IHD, heart failure, aortic stenosis (Heyde syndrome), peripheral vascular disease
- Why: CVS risk factors → ischaemic colitis; HF → susceptible to fluid overload during resuscitation; aortic stenosis → angiodysplasia [2]
- SOB at rest or on exertion
- Why: Anaemia symptoms; cardiopulmonary disease → more susceptible to hypoxaemia [2]
- Easy bruising, prolonged bleeding from cuts, heavy periods
- Why: Underlying bleeding disorder may be the reason bleeding is disproportionate [7]
- Previous bleeding episodes — When? What investigation? What treatment? [5]
- Peptic ulcer disease — Could this be an upper GI source? [1]
- IBD — Known diagnosis? On treatment?
- Previous colonoscopy / polypectomy — When? Findings? [5]
- Chronic liver disease — Coagulopathy, varices [1]
- Heart failure or renal failure — Fluid management implications [2]
- Hereditary haemorrhagic telangiectasia — Angiodysplasia [1]
- Connective tissue disorders — Ehler-Danlos [7]
- Abdominal aortic aneurysm (AAA) repair with graft → DDx: aorto-enteric fistula (herald bleed → massive exsanguination) [1]
- Gastroenteric anastomosis → DDx: marginal ulcers [1]
- Previous colorectal surgery → anastomotic bleeding, altered anatomy
- Previous pelvic surgery → adhesions, radiation history
Don't Forget the Aorto-Enteric Fistula
Any patient with a history of AAA repair presenting with GI bleeding must be considered to have an aorto-enteric fistula until proven otherwise. This is a life-threatening emergency. Students almost always miss this. A "herald bleed" (small initial bleed) can precede catastrophic haemorrhage. [1]
This is consistently highlighted across all lecture slides and notes. [1][2][5]
| Drug Class | Relevance | Cantonese |
|---|---|---|
| NSAIDs | Peptic ulcers, small bowel ulcers, colitis [2][6] | 你有冇食止痛藥？ |
| Aspirin | ↑ bleeding risk, peptic ulcers [1] | 你有冇食薄血丸或者阿士匹靈？ |
| Antiplatelets (clopidogrel) | ↑ bleeding risk [1][2] | |
| Anticoagulants (warfarin, DOACs) | ↑ bleeding risk [1][2][5] | |
| Iron supplements | Can cause black stool (must distinguish from melena) [1] | 你有冇食鐵丸？ |
| Antibiotics | C. difficile-associated colitis [6] | 最近有冇食過抗生素？ |
| Traditional Chinese medicine | May contain steroids → GI ulceration [1] | 有冇食中藥？ |
| Steroids | ↑ ulcer risk |
- Allergies: "你有冇對咩藥物敏感？" (Any drug allergies?)
- Colorectal cancer — First-degree relative with CRC → significantly elevated risk [3][5]
- Familial polyposis syndromes (FAP, Lynch syndrome)
- IBD — Family predisposition
- Bleeding disorders — Haemophilia, von Willebrand disease [7]
"你屋企人有冇人試過大腸癌或者腸瘜肉？" (Has anyone in your family had bowel cancer or polyps?)
| Domain | Questions | Why It Matters |
|---|---|---|
| Smoking | 你有冇食煙？食咗幾耐？每日幾多支？ | Risk factor for CRC and peptic ulcers [1] |
| Alcohol | 你飲唔飲酒？飲幾多？ | Chronic liver disease → varices, coagulopathy [1] |
| Diet | High red/processed meat, low fibre | CRC risk factors |
| Sexual history | If appropriate — MSM, receptive anal intercourse | Proctitis (gonorrhoea, HSV, chlamydia) [6] |
| Travel history (TOCC) | 最近有冇去旅行？去邊度？ | Endemic areas for parasitic infections (amebiasis) [6] |
| Occupation | Prolonged sitting/standing | Haemorrhoid risk |
| Functional baseline | ADLs, mobility, exercise tolerance | Pre-morbid fitness affects surgical candidacy |
These findings should prompt immediate escalation to a senior clinician/surgeon:
- Haemodynamic instability — Hypotension (SBP < 90), tachycardia (> 100), confusion, syncope [2]
- Massive ongoing haematochezia — Not settling, requiring transfusion
- Suspected aorto-enteric fistula — History of AAA graft + GI bleed [1]
- Signs of peritonism — Guarding, rebound tenderness → perforation/ischaemic bowel
- Massive transfusion requirement — >6 units pRBC [2]
- Anticoagulant use with uncontrolled bleeding [2]
- Suspected upper GI source — Haematemesis, coffee-ground vomitus, haemodynamic instability disproportionate to PR bleeding [2]
Common Student Mistakes
- Forgetting to exclude upper GI bleed — 10–15% of haematochezia is from massive UGIB. Always ask about haematemesis, coffee-ground vomitus, and melena. [2]
- Not asking about the relationship of blood to stool — This is the single most localising question and students routinely skip it.
- Ignoring drug history — NSAIDs, antiplatelets, and anticoagulants are consistently tested. [1][2][5]
- Not asking about recent procedures — Post-polypectomy bleeding is an important and easily missed cause. [1][5]
- Forgetting iron supplements — Black stool from iron ≠ melena. Ask specifically. [1]
- Not asking about AAA repair — Aorto-enteric fistula is rare but lethal and always asked in exams. [1]
- Skipping constitutional symptoms and family history — These are the CRC red flags examiners specifically look for. [5]
- Assuming haemorrhoids in a young patient without exclusion of other causes — Haemorrhoids are common but should be a diagnosis of exclusion in someone with red flags.
- Not checking haemodynamic status first — In an OSCE, verbalise: "Before taking a detailed history, I would assess haemodynamic stability."
- "75% of lower GI bleeding stops spontaneously" [2] — This is a favourite exam fact. It means that most LGIB is self-limiting, but you still need to find the cause.
- Right-sided diverticula are more common in Asians (cf. left-sided in Western populations) and have a higher risk of haemorrhage. [1] — HKU loves this.
- Hb does NOT reflect acute blood loss — It takes ≥24 hours for haemodilution to occur. A normal Hb in the ED does NOT mean the patient hasn't bled significantly. [2]
- Colour of blood is a rough guide only — Fresh PR blood (鮮紅色) = distal to splenic flexure; Dark PR blood (暗紅色) = proximal to splenic flexure. [3]
- Diverticular bleeding occurs in the absence of diverticulitis — A common misconception. Bleeding and inflammation are separate complications. [1]
- Colonoscopy diagnostic yield = 75–90% and should be performed early. [2]
- 99mTc-labelled RBC scan is more sensitive than angiography for GI bleeding (min bleeding rate 0.1–0.4 vs ≥0.5–1 mL/min) and can detect intermittent bleeding with delayed images up to 24h. [8]
Mr Chan is a 68-year-old gentleman who presented 2 days ago to Queen Mary Hospital with a 3-day history of painless, profuse, bright red per-rectal bleeding. He describes passing large volumes of fresh blood by itself without stool on approximately 6 occasions. He denies any abdominal pain, change in bowel habit, tenesmus, mucus per rectum, or constitutional symptoms such as weight loss or loss of appetite. There is no haematemesis or coffee-ground vomitus. He reports feeling light-headed on standing and has had one syncopal episode.
His past medical history is significant for hypertension, hyperlipidaemia, and type 2 diabetes mellitus. He had a right hemicolectomy 5 years ago for a benign adenomatous polyp. He has no history of inflammatory bowel disease, liver disease, or previous GI bleeding.
His past surgical history includes the right hemicolectomy as mentioned, and an open appendicectomy in childhood. He has had no aortic surgery.
His regular medications include aspirin 80 mg daily, atorvastatin 40 mg daily, metformin 500 mg BD, and amlodipine 5 mg daily. He has no known drug allergies.
His family history is notable for a brother diagnosed with colorectal carcinoma at age 72. There is no family history of inflammatory bowel disease or polyposis syndromes.
Socially, Mr Chan is a retired bus driver. He is an ex-smoker with a 30 pack-year history, having quit 10 years ago. He drinks alcohol socially, approximately 2 units per week. He is independent in all activities of daily living and has a good exercise tolerance, able to climb 2 flights of stairs without limitation.
In summary, Mr Chan is a 68-year-old gentleman with cardiovascular risk factors, on aspirin, presenting with acute, painless, profuse haematochezia with haemodynamic compromise including syncope. The leading differential diagnosis is diverticular bleeding given the painless, profuse nature and his age. However, given his family history of colorectal carcinoma and personal history of adenomatous polyp, malignancy must be excluded. I would like to discuss his resuscitation plan, the need for urgent colonoscopy, and whether we should consider a CT angiogram given his haemodynamic instability.
Active Recall - History Taking
High Yield Summary
Lower GI bleed = bleeding distal to ligament of Treitz. Most common presentation is haematochezia. 75% stops spontaneously.
Key history framework: (1) Assess haemodynamic stability FIRST. (2) Characterise the bleeding — nature, colour, relationship to stool, volume, timing. (3) Associated GI symptoms — bowel habit change, pain, anorectal symptoms. (4) Red flags for CRC — age >50, change in bowel habit, constitutional symptoms, family history. (5) Always exclude UGIB (10–15% of haematochezia). (6) Drug history — NSAIDs, antiplatelets, anticoagulants, iron, antibiotics, TCM. (7) Surgical history — AAA repair (aorto-enteric fistula), recent polypectomy. (8) Comorbidities — liver disease (varices/coagulopathy), CKD (platelet dysfunction), CVS disease (ischaemic colitis), HF/RF (fluid overload risk).
Top differentials by age: < 50y = haemorrhoids, IBD, Meckel's. >50y = diverticular disease, angiodysplasia, colorectal carcinoma. All ages = infectious colitis, ischaemic colitis, post-procedure bleeding.
Three things students always forget: (1) Asking about relationship of blood to stool. (2) Excluding UGIB. (3) AAA graft history.
[1] Senior notes: felixlai.md (Lower GI bleeding, sections on differential diagnosis and history taking) [2] Senior notes: Ryan Ho GI.pdf (pp. 107–111, Approach to Lower GI Bleeding — History Taking, Causes, Investigations) [3] Senior notes: maxim.md (Section 4.2 LGIB, DDx table and Section 4.8 Diseases of anal canal) [4] Senior notes: Ryan Ho Fundamentals.pdf (pp. 281–286, Lower GI Bleeding causes and approach) [5] Lecture slides: GC 186. Lower and diffuse abdominal painfresh blood in stool.pdf (pp. 3, 4, 19, 38) [6] Senior notes: felixlai.md (Ulcerative colitis section — differential diagnosis including infectious colitis, radiation colitis, sexual history) [7] Senior notes: Ryan Ho Haemtology.pdf (p. 114, Approach to Bleeding Disorders — history taking) [8] Senior notes: Ryan Ho Diagnostic Radiology.pdf (p. 62, Red Blood Cell Scan for GI bleeding)
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