Ischaemic colitis

Introduction

Ischaemic colitis occurs when there is a temporary or sustained reduction in blood flow to the colon, leading to mucosal injury and inflammation. It most commonly affects watershed areas of the colon, such as the splenic flexure and rectosigmoid junction, which are more susceptible to hypoperfusion. The condition is often transient and self-limiting, but severe cases can lead to bowel necrosis or perforation.

Peak Incidence

• Most commonly affects individuals aged 60 to 80 years.
• Risk factors include hypotension, dehydration, atherosclerosis, cardiac failure, and vasoactive drug use (e.g. diuretics, digoxin).

Pathophysiology

• Reduced perfusion leads to ischaemia of the colonic wall, especially in areas with limited collateral circulation.
• Prolonged or severe ischaemia may result in transmural infarction, necrosis, and potential perforation.
• Restoration of blood flow often leads to recovery, unless complications such as gangrene develop.

Symptoms

Classical Presentation

• Sudden onset of crampy lower abdominal pain, typically in the left lower quadrant
• Urgency to defecate
• Bloody diarrhoea or haematochezia
• Symptoms often self-resolve within 2–3 days

Severe or Gangrenous Colitis

• Persistent or worsening abdominal pain
• Fever
• Systemic signs such as confusion or hypotension may indicate progression

Signs

Local Signs

• Abdominal tenderness
• Reduced or absent bowel sounds (ileus)
• Distension, guarding, or rebound tenderness – suggestive of peritonitis

Systemic Signs

• Features of hypovolaemic shock – e.g. tachycardia, hypotension, dry mucous membranes
• Fever and elevated inflammatory markers may indicate sepsis

Diagnosis

Blood Tests

• FBC – Raised white cell count; possible anaemia
• U&Es – May show hyponatraemia or signs of dehydration
• ABG – May reveal metabolic acidosis
• Lactate – Elevated, indicating tissue hypoperfusion
• LDH – May be raised due to cell injury

Imaging

• CT Abdomen (first-line)
  • Thumbprinting due to submucosal oedema or haemorrhage
  • Bowel wall thickening and peri-colic fat stranding
• Abdominal X-ray
  • May show thumbprinting in moderate cases
  • Used to assess for perforation or toxic megacolon

Complications

• Gangrenous colitis – Transmural infarction and bowel necrosis
• Perforation – May result in peritonitis and sepsis
• Stricture formation – From chronic inflammation and scarring
• Fistula formation – Rare but possible
• Sepsis – From bacterial translocation or perforation
• Recurrence – Common in patients with ongoing risk factors
• Toxic megacolon – Severe colonic dilatation with systemic toxicity

Management

Mild to Moderate Disease

• Address underlying cause (e.g. dehydration, hypotension)
• Bowel rest – Keep the patient nil by mouth
• Intravenous fluids
• Broad-spectrum antibiotics
• Analgesia – Avoid NSAIDs

Severe Disease or Complications

• Surgical intervention if:
  • Evidence of perforation
  • Gangrene seen on imaging or colonoscopy
  • Persistent bleeding or stricture causing obstruction
• ICU transfer for unstable patients:
  • Vasopressors, ventilatory support, and aggressive fluid resuscitation

Chronic or Recurrent Disease

• Modify risk factors to prevent recurrence:

  • Smoking cessation
  • Optimise blood pressure and cardiac function
  • Manage atherosclerosis, arrhythmias, and volume status
  • Consider statins for hypercholesterolaemia