Mesenteric ischaemia

Introduction

Mesenteric ischaemia refers to a reduction in blood supply to the intestines, which impairs the delivery of oxygen and nutrients to the bowel wall. This leads to tissue hypoxia, necrosis, and, if left untreated, bowel infarction. It is a potentially life-threatening condition and is classified into acute mesenteric ischaemia (AMI) and chronic mesenteric ischaemia (CMI).

Peak Incidence

• Both acute and chronic mesenteric ischaemia most commonly occur in individuals over the age of 60.

Pathophysiology

• Acute mesenteric ischaemia is usually caused by:
  • Arterial embolism (e.g. from atrial fibrillation).
  • Arterial thrombosis (usually in atherosclerotic vessels).
  • Non-occlusive ischaemia (e.g. due to hypotension or shock).
  • Venous thrombosis (less common).
• Chronic mesenteric ischaemia results from progressive atherosclerotic narrowing of mesenteric arteries, typically affecting at least two of the major mesenteric vessels (e.g. coeliac, superior mesenteric, and inferior mesenteric arteries).

Symptoms

Acute Mesenteric Ischaemia

• Sudden onset of severe abdominal pain – Pain is often disproportionate to physical findings.
• Nausea and vomiting.
• Diarrhoea – May become bloody if bowel necrosis develops.
• Abdominal distension – In later stages with infarction or ileus.

Chronic Mesenteric Ischaemia

• Postprandial abdominal pain – Typically begins 10–30 minutes after eating and resolves within a few hours.
• Weight loss – Due to “food fear” from recurrent pain.
• Nausea and bloating – Related to delayed gastric emptying and reduced gut perfusion.

Signs

Acute Mesenteric Ischaemia

• Generalised or periumbilical tenderness.
• Reduced or absent bowel sounds – Suggests infarction.
• Guarding or rebound tenderness – Suggests peritonitis.
• Shock – Tachycardia, hypotension, cold extremities, or altered mental status.

Chronic Mesenteric Ischaemia

• Mild abdominal tenderness.
• Abdominal bruit – May be heard over the epigastrium due to turbulent flow in narrowed vessels.
• Cachexia – From prolonged malnutrition.

Diagnosis

Acute Mesenteric Ischaemia

• CT angiography (CTA) – First-line and gold standard.
  • Can identify vascular occlusion, bowel wall thickening, pneumatosis intestinalis, and mesenteric oedema.
• ECG – May show atrial fibrillation (risk factor for embolic cause).
• Blood tests:
  • Elevated lactate – Marker of tissue hypoxia and poor perfusion.
  • Leucocytosis – Suggests systemic inflammation or sepsis.
  • Metabolic acidosis – Due to lactic acid accumulation.

Chronic Mesenteric Ischaemia

• CT angiography (CTA) – Preferred imaging to assess atherosclerotic narrowing.
• Doppler ultrasound – May show high-velocity flow in narrowed mesenteric arteries.
• MR angiography (MRA) – Useful alternative if CTA is contraindicated (e.g. due to renal impairment or contrast allergy).

Complications

Acute Mesenteric Ischaemia

• Bowel infarction – Leading to sepsis, peritonitis, and multi-organ failure.
• Bowel perforation – From transmural necrosis.
• Septic shock – Due to bacterial translocation.

Chronic Mesenteric Ischaemia

• Malnutrition and cachexia – From reduced oral intake.
• Bowel obstruction – Due to fibrosis or extensive vascular insufficiency.

Management

Acute Mesenteric Ischaemia

• Initial resuscitation:
  • IV fluids – To restore perfusion.
  • Broad-spectrum antibiotics – To prevent or treat sepsis.
• Anticoagulation – To prevent further thrombus formation (e.g. with heparin).
• Emergency laparotomy – Indicated if there are signs of peritonitis or bowel infarction.
• Endovascular options (if patient is haemodynamically stable):
  • Mechanical thrombectomy or embolectomy.
  • Angioplasty ± stenting.
  • Catheter-directed thrombolysis (e.g. with alteplase) or vasodilators (e.g. papaverine).

Chronic Mesenteric Ischaemia

• Lifestyle changes:

  • Smoking cessation.
  • Dietary optimisation and nutritional support.

• Pharmacological treatment:

  • Statins – To reduce atherosclerotic progression.
  • Antiplatelet therapy – To reduce the risk of thrombosis (e.g. aspirin).

• Revascularisation:

  • Endovascular therapy (first-line) – Angioplasty with or without stenting.
  • Surgical bypass – Reserved for patients who fail endovascular management or in cases of extensive vascular disease.