PassFinals
Colorectal Surgery

Intestinal Ischaemia

Inadequate blood supply to the gut, spanning three entities that differ in vessel, tempo and danger: acute mesenteric ischaemia (a small-bowel emergency), chronic mesenteric ischaemia (intestinal angina from symptomatic mesenteric arterial disease), and ischaemic colitis (usually a low-flow colonic injury); telling them apart drives urgency.

In a nutshell

Intestinal ischaemia has three forms: acute mesenteric ischaemia (SMA occlusion, small-bowel emergency, pain out of proportion, high mortality), chronic mesenteric ischaemia (postprandial pain and weight loss from atherosclerosis), and ischaemic colitis (low-flow colonic injury, bloody diarrhoea, usually self-limiting). Distinguishing them sets the urgency.

Classic presentation

Sudden severe abdominal pain out of proportion in an AF patient (acute mesenteric ischaemia); postprandial pain with weight loss (chronic); or crampy left-sided pain then bloody diarrhoea (ischaemic colitis).

Key points

  • Acute mesenteric ischaemia is a small-bowel emergency: pain out of proportion, urgent CT angiography, high mortality.
  • Chronic mesenteric ischaemia is intestinal angina: postprandial pain, food fear and weight loss from multi-vessel atherosclerosis.
  • Ischaemic colitis is a low-flow injury of the colonic watershed zones, usually self-limiting.
  • A normal lactate early does not exclude acute mesenteric ischaemia.
  • Atrial fibrillation points to an embolic SMA occlusion.

First-line investigation

CT angiography of the mesenteric vessels, with serum lactate to gauge infarction.

Management

Identify the dangerous phenotype

  • Pain out of proportion, peritonism, shock or bleeding with low-flow physiology should trigger the acute mesenteric-ischaemia pathway and immediate senior multidisciplinary escalation.1,3

Image and classify

  • Use urgent biphasic CT angiography for acute presentations; use fasting duplex and then CTA for suspected chronic mesenteric ischaemia, and CT with safe limited endoscopy for ischaemic colitis.1,3,2

Treat acute and chronic arterial disease

  • Acute disease needs urgent revascularisation and resection of non-viable bowel; symptomatic chronic disease needs specialist mesenteric revascularisation, usually endovascular when suitable.1,3

Support ischaemic colitis

  • Uncomplicated ischaemic colitis is usually supported with fluids, electrolyte correction, early nutrition when safe and severity-guided antimicrobials; peritonitis, perforation, gangrene or deterioration require surgery.2,5,4

Treat cause and surveil

  • Address embolic, venous, low-flow and atherosclerotic causes, arrange post-revascularisation clinical and imaging follow-up, and involve nutritional or intestinal-failure services when bowel length is reduced.1,3,4

Exam traps

  • Do not confuse ischaemic colitis (low-flow, colon, usually self-limiting) with acute mesenteric ischaemia (SMA occlusion, small bowel, high mortality).
  • Pain out of proportion to a soft abdomen is the early warning of acute mesenteric ischaemia.
  • A normal early lactate is falsely reassuring in acute mesenteric ischaemia.
  • Weight loss with postprandial pain is chronic mesenteric ischaemia, not simply functional dyspepsia.

Illustrations

Ischaemic colitis on contrast CTMulti-planar contrast CT showing a long segment of thickened, oedematous colon in ischaemic colitis, one of the major clinical patterns of intestinal ischaemia.Hellerhoff, Wikimedia Commons · CC-BY-SA-4.0

Key sources

  1. ESVS 2025 Guidelines on Diseases of the Mesenteric and Renal Arteries and Veins (Current specialist vascular guideline covering chronic and acute arterial mesenteric ischaemia, non-occlusive disease and mesenteric venous thrombosis; includes diagnostic imaging, specialist-centre care, revascularisation, antibiotics, anticoagulation and follow-up.)
  2. BMJ clinical update: Ischaemic colitis (UK clinical update covering urgent admission, contrast CT, endoscopic confirmation, supportive treatment, surgical indications, antimicrobial uncertainty and follow-up for ischaemic colitis.)
  3. World Society of Emergency Surgery: Acute mesenteric ischaemia updated guidelines (International emergency-surgery guideline used because there is no dedicated NICE or UK national acute-mesenteric-ischaemia guideline; covers acute diagnosis, resuscitation, antibiotics, urgent surgery, revascularisation and second-look assessment.)
  4. BNF online: current anticoagulant, analgesic and antimicrobial prescribing (Use the current BNF and local surgical, vascular and antimicrobial protocols for drug selection, dosing, renal adjustment, contraindications, interactions, duration and monitoring; no fixed regimen is reproduced here.)
  5. NICE NG89: Venous thromboembolism in over 16s (NICE VTE-prevention guidance relevant to peri-operative risk assessment and prophylaxis when safe; it is not a disease-specific treatment guideline for intestinal ischaemia.)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.