ICU ·

Toxic megacolon and acute severe colitis

Also known as Toxic megacolon · Acute severe ulcerative colitis (ASUC) · Fulminant colitis · C. difficile colitis · Pseudomembranous colitis · Toxic dilation of the colon · Truelove-Witts severe UC · Subtotal colectomy · Infliximab rescue · Cyclosporine rescue · CONSTRUCT trial

Toxic megacolon is a life-threatening complication of severe colonic inflammation characterised by non-obstructive colonic dilatation greater than 6 cm with systemic toxicity (fever, tachycardia, leucocytosis, anaemia). The classic causes are ulcerative colitis and Clostridium difficile colitis; other infectious causes include Salmonella, Shigella, Campylobacter, CMV and E. coli O157, and ischaemic colitis is also recognised. Diagnosis rests on clinical toxicity plus plain abdominal radiography, with CT an alternative that adds information. Management is interdisciplinary from the outset: fluid and electrolyte correction, broad-spectrum antibiotics including metronidazole (with enteral vancomycin for pseudomembranous colitis), corticosteroids for inflammatory causes, and subtotal colectomy with terminal ileostomy for perforation, peritonitis, massive haemorrhage or failed medical therapy. In acute severe ulcerative colitis, day-3 objective reassessment (stool count and CRP) drives escalation to infliximab or ciclosporin rescue.

Checked against its sources on 5 Sept 2026