Key Facts

Ischaemic colitis is the most common form of intestinal ischaemia. It usually presents in elderly patients with cardiovascular risk factors. The vast majority of cases are non-gangrenous and self-limiting with supportive care.

Epidemiology

Incidence ~16-22 per 100,000 per year; increasing with aging population. Accounts for 1 in 2000 hospital admissions. Mean age at presentation ~70 years. Female slight predominance. Accounts for ~50% of all mesenteric ischaemia.

Aetiology

• Non-occlusive (most common): reduced colonic perfusion in low-flow states (hypotension, cardiac failure, post-cardiac surgery, dehydration)
• Small vessel disease: diabetes, vasculitis, amyloidosis, radiation
• Occlusive: IMA thrombosis/embolism (rare), aortic surgery (IMA ligation), aortic dissection
• Medications: digoxin, vasopressors, oestrogens, cocaine, NSAIDs
• Other: hypercoagulable states, long-distance running ("runner's colitis")

Pathophysiology

The colon receives blood supply from the SMA (right colon) and IMA (left colon/rectum). Watershed areas (splenic flexure, rectosigmoid junction) are most vulnerable to low-flow ischaemia. Reduced perfusion → mucosal ischaemia → oedema, haemorrhage → if severe → transmural infarction → gangrene → perforation. The rectum is relatively spared due to dual blood supply (IMA + internal iliac).

Typical Presentation

• Sudden-onset crampy LIF/lower abdominal pain
• Bloody diarrhoea (bright red or maroon) — usually within 24 hours of pain onset
• Urgency to defaecate
• Mild abdominal tenderness (usually LIF)
• Low-grade fever

Gangrenous/Severe

• Severe abdominal pain with peritonitis
• Systemic sepsis (fever, tachycardia, hypotension)
• Absent bowel sounds
• Rapidly deteriorating clinical picture

Red Flags

• Peritonitis (guarding, rebound) — gangrenous colitis, possible perforation
• Haemodynamic instability
• No improvement after 2-3 days of supportive care
• Recurrent episodes (consider underlying vascular disease or hypercoagulable state)

Bedside

• A-E assessment: haemodynamic status
• DRE: blood on glove
• ABG/VBG: lactate (raised if severe), metabolic acidosis (gangrenous disease)

Bloods

• FBC: leucocytosis
• CRP: raised (may be markedly elevated in gangrenous disease)
• Lactate: raised in severe/gangrenous disease
• U&Es: dehydration, AKI
• LDH: may be raised
• Stool MC&S + C. diff toxin: exclude infective colitis

Imaging

• CT abdomen with IV contrast: first-line — segmental colonic wall thickening ("target sign" or "double halo sign"), pericolonic stranding, in a watershed distribution; no involvement of rectum (distinguishes from UC); may show pneumatosis in gangrenous disease
• AXR: non-specific; may show thumbprinting (mucosal oedema)

Endoscopy

• Flexible sigmoidoscopy/colonoscopy: gold standard for diagnosis (once stable); findings:
  • Segmental involvement with sharp demarcation between ischaemic and normal mucosa
  • Oedematous, haemorrhagic, friable mucosa
  • Coagulative necrosis ("single stripe sign" — linear ulceration along antimesenteric border)
  • Biopsy: mucosal necrosis, haemosiderin-laden macrophages, crypt withering
  • Avoid air insufflation if gangrenous disease suspected (risk of perforation)

Non-pharmacological

• Supportive care (non-gangrenous): IV fluids, bowel rest (clear fluids initially), monitor closely
• Cardiac optimisation: correct hypotension, optimise cardiac output
• Stop offending medications: vasoconstrictors, NSAIDs, oestrogens

Pharmacological

• Antibiotics: if signs of sepsis or gangrenous disease — piperacillin-tazobactam 4.5 g TDS or co-amoxiclav 1.2 g TDS + metronidazole 500 mg TDS
• VTE prophylaxis: LMWH (patients are at risk of DVT/PE)
• Manage cardiovascular risk factors: statins, antihypertensives, antiplatelet therapy as appropriate

Surgical/Interventional

• Emergency colectomy: for gangrenous colitis, perforation, or clinical deterioration despite maximal medical therapy; usually segmental resection with end stoma (Hartmann's procedure)
• Second-look laparotomy: may be needed at 24-48 hours to reassess bowel viability

Referral Criteria

• All suspected ischaemic colitis: surgical and gastroenterology review
• ITU/HDU: gangrenous disease or haemodynamic instability
• Follow-up colonoscopy: 6-8 weeks after episode to confirm resolution and exclude underlying pathology (CRC)

Non-gangrenous ischaemic colitis: 80-85% of cases resolve with supportive care within 1-2 weeks. Mortality for non-gangrenous disease is ~5%. Stricture formation occurs in ~10-15% as a late complication (may need surgical resection). Gangrenous ischaemic colitis: mortality 50-65%. Recurrence rate ~10%. Right-sided ischaemic colitis has worse prognosis than left-sided (often reflects more severe cardiovascular disease or mesenteric ischaemia).

Non-gangrenous vs Gangrenous Ischaemic Colitis

Watershed Areas of the Colon