Ulcerative Colitis

🧭 When to suspect

Ulcerative colitis (UC) is a chronic, relapsing–remitting inflammatory bowel disease in which continuous mucosal inflammation extends proximally from the rectum for a variable distance – from proctitis alone, through left-sided disease, to extensive colitis / pancolitis. Inflammation is confined to the colon and is limited to the mucosa and submucosa, which is what distinguishes it from the transmural, patchy, mouth-to-anus pattern of Crohn's disease.

Suspect UC in anyone with diarrhoea containing visible blood or mucus persisting for more than 6 weeks, typically with rectal urgency, tenesmus, and crampy left lower quadrant pain. Nocturnal diarrhoea and rectal bleeding point strongly to organic disease and help separate UC from irritable bowel syndrome; a raised faecal calprotectin supports inflammation and is the key primary-care test for triaging who needs gastroenterology referral. Be alert to extra-intestinal manifestations – arthropathy, erythema nodosum, episcleritis/uveitis, aphthous ulcers – which may precede or accompany bowel symptoms.

The two key clinical skills in primary care are twofold: assess disease severity using the Truelove and Witts' criteria, and never miss acute severe colitis or toxic megacolon, which are medical emergencies. Drug choice for induction and maintenance is then driven largely by disease extent.

An acute severe flare – ≥ 6 bloody stools per day with any systemic feature – mandates emergency admission for intravenous corticosteroids, not outpatient management.

Source: NICE NG130 · NICE DG11 · BSG IBD 2025