Makindo Medical Notes

⚠️ Toxic Megacolon is a potentially lethal complication of severe colitis, defined radiologically by a transverse colon diameter >6 cm with systemic toxicity. Physical findings may be blunted in patients with inflammatory bowel disease who have received high-dose steroids.

📖 About

• Represents the end-point of severe colitis, with dilated, atonic colon and systemic toxicity.
• A colorectal surgeon should review patients with acute severe UC early in admission.
• Mortality remains high, especially if perforation occurs.

🧬 Aetiology

• Acute colonic distension with loss of tone.
• Severe transmural inflammation → damage extends into smooth muscle, impairing peristalsis.
• Ileus worsens dilatation, leading to a vicious cycle.
• Deep mucosal ulceration predisposes to perforation.

⚡ Causes

• Inflammatory bowel disease (Ulcerative Colitis > Crohn’s).
• Infective colitis – especially C. difficile pseudomembranous colitis.
• Ischaemic colitis, radiation colitis.

🩺 Clinical Features

• Systemically unwell: fever, tachycardia, dehydration, shock.
• Abdominal distension, tenderness, pain.
• Signs of perforation: rigid abdomen, rebound tenderness, peritonitis.
• Patients with steroids may have attenuated clinical signs despite severe disease.

🔍 Differentials of Colonic Dilatation

• Hirschsprung’s disease – usually systemically well.
• Idiopathic megacolon / chronic constipation – well, chronic course.
• Ogilvie syndrome (acute colonic pseudo-obstruction) – well, often postoperative/medication-related.
• Large bowel obstruction (cancer, volvulus, strictures).

🧪 Investigations

• Bloods: FBC, U&E, CRP, group & save, clotting.
• AXR: Mid-transverse colon >6–7 cm, loss of haustra, mucosal oedema, absence of faeces.
• CT Abdomen: Confirms dilatation, assesses complications (perforation, abscess).
• Endoscopy: Avoided due to perforation risk.

⚕️ Management – MDT with Surgeons & Gastroenterology

• General Support: ABC, IV fluids, nil by mouth, NG tube aspiration, analgesia, ITU/HDU if unstable.
• Medical: – IV corticosteroids (methylprednisolone). – Stop opioids, loperamide, NSAIDs, and anticholinergics. – VTE prophylaxis, nutritional support, antibiotics if infection suspected. – Twice daily monitoring of abdominal girth.
• IBD-related: If no response to IV steroids after 3–5 days → Ciclosporin or Infliximab may avoid colectomy.
• C. difficile: Oral/NG vancomycin ± IV metronidazole. Consider colonoscopic decompression or intracolonic vancomycin in refractory cases. IVIG infusion is a salvage therapy.
• Surgical: Urgent colorectal review. Options: subtotal or total colectomy ± ileostomy if perforation, necrosis, or failed medical therapy.

📚 References

• BSG Guidelines: Acute Severe Ulcerative Colitis
• Toxic Megacolon – StatPearls

3 Clinical Cases — Toxic Megacolon 🚨🧻

• Case 1 — Ulcerative colitis complication 🩸: A 28-year-old man with known extensive ulcerative colitis presents with abdominal distension, severe pain, fever (39°C), and tachycardia. Abdomen: tender, tympanic. AXR: transverse colon dilated to 8.5 cm. Teaching: Inflammatory bowel disease (especially UC) is a classic cause of toxic megacolon. Management: urgent IV steroids, fluids, broad-spectrum antibiotics, and surgical review. Risk of perforation is high if untreated.
• Case 2 — Infective trigger (C. difficile) 🦠: A 74-year-old woman on recent broad-spectrum antibiotics develops profuse diarrhoea, abdominal distension, and hypotension. AXR: gross colonic dilatation, particularly in the right colon. Stool toxin positive for Clostridioides difficile. Teaching: Severe C. diff infection can precipitate toxic megacolon. Management: stop inciting antibiotics, give oral vancomycin ± IV metronidazole, supportive care, and early surgical input if deterioration.
• Case 3 — Crohn’s disease flare 🌿: A 35-year-old woman with known Crohn’s colitis presents with abdominal pain, high fever, and progressive distension. CXR: dilated colon with loss of haustrations, no free air. Teaching: Though less common than UC, Crohn’s colitis can cause toxic megacolon. The systemic toxicity (fever, tachycardia, shock) plus dilated colon >6 cm defines the diagnosis. Requires ICU-level support, steroids, antibiotics, and urgent surgical involvement.