Bloody diarrhea with urgency — ulcerative colitis; colonoscopy confirms continuous inflammation. UC (continuous mucosal — rectum upward: bloody diarrhea, urgency, tenesmus): 5-ASA (mesalamine) + steroids for flares, biologics (infliximab) for severe; cancer surveillance colonoscopy. Crohn's (skip lesions, transmural — anywhere mouth to anus: pain, fistulas, strictures; steroids, azathioprine, anti-TNF). Celiac (gluten — tTG-IgA positive, villous atrophy: gluten-free diet). IBS (functional — Rome: pain + altered bowels, no alarm features: fiber, antispasmodics, reassurance). The bloody urgency is inflammatory — alarm features forbid the IBS label.