Ulcerative colitis
Definition and epidemiology
Ulcerative colitis (UC) is a chronic, relapsing-remitting, non‑infectious inflammatory disorder confined to the large bowel. It causes continuous, superficial (mucosal) inflammation beginning in the rectum and extending proximally for a variable distance; it does not extend beyond the ileocaecal valve. There are bimodal incidence peaks at approximately 15-25 years and 55-65 years.
Pathology (key features)
- Mucosa: erythematous, friable, bleeds easily; widespread superficial ulceration.
- Pseudopolyps: islands of regenerating mucosa.
- Histology: crypt architectural distortion, neutrophil crypt abscesses, depletion of goblet cells.
- Depth of inflammation: typically limited to mucosa and submucosa; transmural disease suggests Crohn’s disease.
- Granulomas are unusual and should prompt consideration of alternative diagnoses.
Risk factors and important associations
- Positive family history increases risk.
- Smoking appears protective against developing UC (contrasts with Crohn’s disease).
- Appendicectomy in childhood may be protective.
- NSAIDs can precipitate or worsen disease activity.
- Primary sclerosing cholangitis (PSC) is strongly associated with UC.
- Active UC confers an increased venous thromboembolism (VTE) risk (≥2× general population), highest during flares - perform inpatient VTE risk assessment and provide prophylaxis when appropriate (NICE QS201).