Key Facts

Ulcerative colitis is a chronic relapsing-remitting inflammatory bowel disease characterised by diffuse mucosal inflammation of the colon, always involving the rectum and extending proximally in a continuous fashion.

Epidemiology

UK prevalence is approximately 240 per 100,000 (higher than Crohn's). Incidence is ~10-12 per 100,000 per year. Peak onset 15-25 years (second smaller peak at 55-65). Equal sex distribution. More common in non-smokers and ex-smokers (smoking is paradoxically protective). Higher in Northern European, North American, and Jewish populations.

Aetiology

• Genetics: >200 susceptibility loci; HLA-DRB1; IL-10; weaker genetic component than Crohn's
• Smoking: paradoxically PROTECTIVE; disease often presents/flares after smoking cessation
• Appendicectomy: protective effect (~70% reduced risk)
• Microbiome: reduced diversity, decreased Firmicutes
• Environmental: stress, NSAIDs, infections can trigger flares

Pathophysiology

UC involves a dysregulated mucosal immune response with Th2 polarisation (IL-5, IL-13 predominant). Epithelial barrier dysfunction allows bacterial translocation, triggering NF-κB-mediated inflammation. Unlike Crohn's, inflammation is confined to the mucosa and submucosa, with crypt abscesses and goblet cell depletion being characteristic histological findings. Continuous inflammation from the rectum proximally (no skip lesions) distinguishes UC from Crohn's colitis.

Mild UC

• <4 bloody stools/day
• No systemic features
• Normal inflammatory markers

Moderate UC

• 4-6 bloody stools/day
• Mild systemic features
• Mildly raised CRP

Acute Severe UC (Truelove & Witts Criteria)

• ≥6 bloody stools/day PLUS ≥1 of:
  • Pulse >90 bpm
  • Temperature >37.8°C
  • Hb <105 g/L
  • ESR >30 mm/hr or CRP >30 mg/L
• Medical emergency — requires hospital admission

Extra-Intestinal Manifestations

• Similar to Crohn's but PSC is more common in UC (up to 5%)
• Erythema nodosum, pyoderma gangrenosum, anterior uveitis
• Peripheral arthropathy, sacroiliitis/AS
• VTE risk increased (especially during flares)

Red Flags

• Acute severe UC (Truelove & Witts criteria)
• Toxic megacolon (colonic dilatation >6 cm + systemic toxicity)
• Perforation (acute abdomen, free air)
• Massive haemorrhage

Bedside

• Stool: faecal calprotectin (>200 strongly suggests IBD), stool cultures + C. difficile toxin (exclude infective cause)
• Abdominal X-ray: if acute severe UC — assess for toxic megacolon (>6 cm), mucosal islands, free air

Bloods

• FBC: anaemia, raised platelets
• CRP/ESR: disease activity (raised CRP is poor prognostic marker in acute severe UC)
• Albumin: low in severe disease (prognostic)
• U&Es, LFTs: baseline; LFTs for PSC screening
• TPMT/NUDT15: before thiopurines

Imaging

• AXR: toxic megacolon assessment in acute severe UC
• CT abdomen: if complications suspected (perforation, abscess)

Special Tests

• Colonoscopy + biopsies: gold standard — continuous inflammation from rectum, loss of vascular pattern, mucosal erythema/friability, pseudopolyps
  • Histology: crypt abscesses, crypt architectural distortion, goblet cell depletion, chronic inflammatory infiltrate
• Flexible sigmoidoscopy: safer than full colonoscopy in acute severe UC
• Travis (Oxford) criteria: for predicting steroid failure in acute severe UC — day 3: stool frequency >8/day OR CRP >45 mg/L + stool frequency 3-8/day → 85% risk of colectomy

Non-pharmacological

• MDT approach: gastroenterologist, IBD nurse, dietitian, surgeon
• VTE prophylaxis: LMWH for all inpatients with active UC
• Nutritional support: iron replacement, dietitian review

Pharmacological

• Inducing remission (mild-moderate):
  • 5-ASA (mesalazine): topical (rectal foam/suppository) for proctitis; oral mesalazine 2.4-4.8 g/day for more extensive disease (NICE NG130)
  • If 5-ASA insufficient: oral prednisolone 40 mg/day tapering over 8 weeks
• Acute severe UC (inpatient):
  • IV hydrocortisone 100 mg QDS + VTE prophylaxis + stool chart + daily bloods
  • Assess response at day 3 (Travis/Oxford criteria)
  • If failing IV steroids: rescue therapy — infliximab 5 mg/kg IV (ACT 1/2 trials) OR ciclosporin 2 mg/kg/day IV (Lichtiger protocol)
  • If rescue fails: emergency subtotal colectomy
• Maintaining remission:
  • 5-ASA (mesalazine): first-line maintenance; oral ± topical
  • Thiopurines: azathioprine 2-2.5 mg/kg/day — if steroid-dependent or frequent relapse
  • Biologics: infliximab, adalimumab, vedolizumab (anti-α4β7), tofacitinib (JAK inhibitor), upadacitinib, ozanimod (S1P modulator) — for moderate-severe refractory UC

Surgical/Interventional

• Proctocolectomy + ileal pouch-anal anastomosis (IPAA/J-pouch): curative; gold standard elective surgery
• Subtotal colectomy + end ileostomy: emergency operation for toxic megacolon, perforation, or failed medical rescue
• Subsequent completion proctectomy ± IPAA
• Pouchitis: common complication of IPAA (up to 50%) — treat with metronidazole 400 mg TDS or ciprofloxacin 500 mg BD

Referral Criteria

• All IBD to gastroenterology
• Urgent surgical review: acute severe UC failing medical therapy, toxic megacolon
• Colorectal cancer surveillance from 8 years post-diagnosis

UC follows a relapsing-remitting course. ~50% are in remission at any time. 20% will require colectomy within 10 years of diagnosis. Acute severe UC carries ~1% mortality with modern management. Toxic megacolon has ~5-10% mortality. Colorectal cancer risk is increased after 8-10 years of extensive colitis (~1% per year cumulative risk in pancolitis). Regular surveillance colonoscopy reduces cancer mortality. Proctocolectomy is curative but IPAA-related complications (pouchitis, reduced fertility in women) must be considered.

Truelove & Witts Severity Classification

Acute Severe UC Management Timeline