Makindo Medical Notes

🌡️ Intestinal Ischaemia refers to insufficient blood flow to the small or large intestine, causing tissue hypoxia, cellular injury, and if untreated, necrosis. It is a life-threatening emergency with mortality rates >50% if diagnosis is delayed. Early recognition is crucial — especially in elderly patients with cardiovascular risk factors or acute abdominal pain “out of proportion” to clinical findings.

📖 Types of Intestinal Ischaemia

• Acute Mesenteric Ischaemia (AMI) ⚡ – sudden interruption of blood supply, usually superior mesenteric artery (SMA).
• Chronic Mesenteric Ischaemia (CMI) 🕰️ – gradual narrowing due to atherosclerosis → “abdominal angina”.
• Ischaemic Colitis 💢 – most common form; often due to watershed hypoperfusion in colon (splenic flexure, rectosigmoid junction).
• Non-Occlusive Mesenteric Ischaemia (NOMI) 💊 – seen in critically ill patients with low cardiac output or vasopressors.
• Mesenteric Venous Thrombosis (MVT) 🩸 – clot in mesenteric veins impairs venous outflow, leading to oedema and infarction.

🧬 Pathophysiology

• Arterial occlusion (embolus, thrombosis) → reduced perfusion → tissue hypoxia → necrosis within hours.
• Venous thrombosis → congestion, oedema, ↓ arterial inflow → ischaemia.
• Hypoperfusion/shock → “watershed” areas vulnerable (splenic flexure, rectosigmoid junction).
• Ischaemia–reperfusion injury: restoration of flow releases ROS and inflammatory mediators → worsening injury and systemic sepsis.

⚠️ Causes & Risk Factors

• 💔 Cardiovascular: AF, recent MI, heart failure, valvular disease (embolic risk).
• 🩸 Vascular: atherosclerosis, aneurysms, arterial dissection, hypercoagulable states.
• 💊 Iatrogenic: vasopressors, digoxin, ergotamine, oral contraceptives.
• 🧪 Haematological: thrombophilias, polycythaemia vera, protein C/S deficiency.
• 🚑 Systemic: shock, sepsis, dehydration, major surgery (esp. cardiac/AAA repair).

🩺 Clinical Features

• Acute Mesenteric Ischaemia:
  • Severe sudden abdominal pain 🔥 “out of proportion” to exam.
  • Early: minimal tenderness, soft abdomen.
  • Later: peritonitis, shock, bloody stools.
• Ischaemic Colitis:
  • Crampy LLQ pain + bloody diarrhoea.
  • Common in elderly with vascular disease.
• Chronic Mesenteric Ischaemia:
  • “Abdominal angina”: postprandial pain 30–60 min after meals.
  • Fear of eating → weight loss, malnutrition.
• Mesenteric Venous Thrombosis: Subacute pain, diarrhoea ± GI bleeding, slower onset than arterial AMI.

🔎 Investigations

• 🧪 Bloods: ↑ Lactate, metabolic acidosis, leukocytosis, ↑ D-dimer (nonspecific).
• 📷 Imaging:
  • CT Angiography – gold standard for AMI (shows arterial occlusion, bowel wall changes, pneumatosis, portal venous gas).
  • CT abdomen/pelvis – venous thrombosis, colitis.
  • Doppler US – useful in chronic disease.
• 💉 Endoscopy: can help confirm ischaemic colitis (pale mucosa, petechiae, ulceration).

📊 Differential Diagnosis of Acute Abdomen

🛠️ Management

Principle: Resuscitate, restore perfusion, treat underlying cause, and resect necrotic bowel if present.

• 🔄 Resuscitation: ABC, high-flow O₂, IV fluids (avoid over-resuscitation in NOMI), NG tube decompression, urinary catheter.
• 🩸 Anticoagulation: Heparin for mesenteric venous thrombosis or arterial occlusion awaiting intervention.
• 💊 Broad-spectrum antibiotics: Cover gut flora (e.g. piperacillin-tazobactam or carbapenem).
• 🚑 Surgical / Endovascular:
  • Open embolectomy or thrombectomy (SMA embolus).
  • Bypass graft or stenting (chronic occlusive disease).
  • Resection of necrotic bowel with second-look laparotomy in 24–48h.
• 💊 Supportive: Avoid vasoconstrictors if NOMI; optimise cardiac output.

📉 Prognosis

• Mortality in acute mesenteric ischaemia remains high (50–80%), largely due to diagnostic delay.
• Ischaemic colitis often self-limiting but can progress to gangrene if severe.
• Chronic mesenteric ischaemia carries better prognosis if treated with revascularisation.

📚 Clinical Pearls

• 🚨 Acute mesenteric ischaemia = pain out of proportion to exam until late peritonitis develops.
• 💉 Always consider CT angiography early in elderly with sudden severe abdominal pain.
• ⚡ Ischaemia–reperfusion injury worsens outcomes → anticipate metabolic acidosis and systemic inflammatory response.
• 🩸 Heparinisation is vital in suspected thrombotic/embolic causes unless contraindicated.
• 👨‍⚕️ Early surgical consult is life-saving.