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Lower gastrointestinal bleeding
In acute rectal bleeding, stabilise and assess severity; an unstable patient has CT angiography to localise the bleeding and treat it by embolisation, and an upper source must be excluded; a stable low-risk patient can be discharged for a planned colonoscopy.
Why it matters in the exam
The typical question describes an older patient with painless fresh red blood per rectum — diverticular bleeding, the most common cause — and asks for the next test. In a patient with a shock index above 1 or instability, CT angiography locates active bleeding and guides embolisation; very urgent colonoscopy is not superior, and colonoscopy within 24 hours after bowel preparation suits a stable admitted patient.
Remember that about 10–15% of patients with red rectal blood and hypotension are actually bleeding from an upper source (duodenal ulcer); so early gastroscopy is considered in an unstable patient. The transfusion threshold is also tested — haemoglobin 7 g/dL, and 8 in a patient with cardiovascular disease — together with the risk tool: an Oakland score of 8 or less allows safe discharge for outpatient investigation.
Common causes differ by picture: diverticulum — heavy painless bleeding; angiodysplasia — recurrent bleeding in older patients; ischaemic colitis — abdominal pain followed by blood; haemorrhoids — fresh blood on the paper; inflammatory bowel disease; and cancer — mainly chronic bleeding with anaemia. As for anticoagulants: warfarin is stopped and reversed with prothrombin complex concentrate in life-threatening bleeding, and aspirin for secondary prevention is usually continued.
Key points
- The common cause — diverticulum, painless bleeding.
- Unstable — CT angiography and embolisation; consider an upper source.
- Stable — colonoscopy within 24 hours.
- Oakland of 8 or less — discharge for investigation.
- Transfusion threshold: 7 g/dL, and 8 in heart disease.
Summary table
| Cause | Picture | Test | Treatment |
|---|---|---|---|
| Diverticulum | Heavy painless bleeding, older patient | CT angiography or colonoscopy | Usually stops; embolisation or endoscopic therapy |
| Angiodysplasia | Recurrent bleeding, anaemia, older patient | Colonoscopy | Argon plasma coagulation |
| Ischaemic colitis | Abdominal pain then blood | CT, colonoscopy | Support, exclude full-thickness ischaemia |
| Upper source | Red blood with shock, high urea | Gastroscopy | Endoscopic therapy |
| Haemorrhoids | Fresh blood on the paper, stable | Rectal examination and anoscopy | Conservative |
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Sources
- ACG Clinical Guideline: Management of Patients With Acute Lower Gastrointestinal Bleeding, 2023 — Risk assessment, CTA, colonoscopy timing
- British Society of Gastroenterology guidelines on the diagnosis and management of acute lower gastrointestinal bleeding, 2019 — Oakland score and transfusion
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 11th edition (2021) — Gastrointestinal bleeding
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.