Pathophysiology
Clinical meaning
Ulcerative colitis involves continuous mucosal inflammation starting at the rectum and extending proximally. Driven by Th2 cytokine response (IL-5, IL-13) with neutrophilic crypt abscesses. Always involves rectum (vs Crohn which can skip). 5-ASA (mesalamine) is first-line for mild-moderate disease. Biologics (infliximab, vedolizumab) for moderate-severe. Increased colorectal cancer risk after 8-10 years requiring surveillance colonoscopy.