A 28-year-old male presents with recurrent bloody diarrhea, tenesmus, and crampy lower abdominal pain for 4 months. Colonoscopy reveals continuous, circumferential mucosal erythema, loss of vascular pattern, and friability extending from the anal verge up to the splenic flexure, with abrupt transition to normal mucosa. Biopsies show crypt architectural distortion, cryptitis, and crypt abscesses confined to the mucosa and submucosa. What is the most likely diagnosis?
- ACrohn disease
- BIschemic colitis
- CCeliac disease
- DUlcerative colitis