A 34-year-old woman with an 11-year history of ulcerative colitis presents with a 6-week flare characterized by 8 bloody stools per day, weight loss, and elevated inflammatory markers (CRP 62, fecal calprotectin 2,400). Ileocolonoscopy reveals the pattern marked **A** in the diagram: continuous inflammation from the rectum with loss of normal vascular pattern, friability, contact bleeding, and scattered inflammatory pseudopolyps. The terminal ileum is normal. Biopsies confirm ulcerative colitis without dysplasia. Based on the endoscopic findings at location **A**, which of the following best describes the key distinguishing feature of ulcerative colitis compared to Crohn disease?
A. Segmental involvement of the colon with sparing of the rectum and preservation of normal vascular pattern
B. Discontinuous skip lesions with cobblestoning and transmural inflammation involving the terminal ileum
C. Patchy inflammation with granulomas and fissuring ulcers extending through all layers of the bowel wall
D. Continuous mucosal inflammation starting in the rectum and extending proximally without skip areas
Explanation
Why "Continuous mucosal inflammation starting in the rectum and extending proximally without skip areas" is right
The pattern marked A demonstrates the pathognomonic feature of ulcerative colitis: continuous mucosal inflammation originating in the rectum and extending proximally in an uninterrupted manner. The clinical vignette explicitly documents continuous inflammation from the rectum through the sigmoid, descending colon, and transverse colon with loss of vascular pattern, friability, and contact bleeding—hallmarks of UC. Histology confirms crypt distortion, basal plasmacytosis, and a chronic lamina propria infiltrate without transmural involvement, granulomas, or skip areas, which are the defining pathologic distinctions of UC from Crohn disease. This continuous pattern is the key diagnostic criterion that anchors the Montreal classification (E1 proctitis, E2 left-sided colitis, E3 pancolitis) and guides surveillance and treatment intensity. [Sleisenger and Fordtran 11e Ch 116; ECCO UC Guidelines 2022]
Why each distractor is wrong
"Discontinuous skip lesions with cobblestoning and transmural inflammation involving the terminal ileum": This describes Crohn disease, not ulcerative colitis. Skip lesions and terminal ileal involvement are characteristic of Crohn disease, which is marked by transmural inflammation and granulomas—features explicitly absent in this patient's biopsies.
"Patchy inflammation with granulomas and fissuring ulcers extending through all layers of the bowel wall": This is a description of Crohn disease pathology. Granulomas and transmural inflammation are not features of UC; the inflammation in UC is limited to the mucosa and submucosa.
"Segmental involvement of the colon with sparing of the rectum and preservation of normal vascular pattern": This contradicts the endoscopic findings at A, which show continuous inflammation starting at the rectum with loss of vascular pattern. UC always involves the rectum and extends proximally without sparing.
High-YieldNEET PG
Ulcerative colitis = continuous mucosal inflammation from rectum proximally, no skip areas, no transmural disease, no granulomas; Crohn disease = skip lesions, transmural, granulomas, can involve any part of GI tract including terminal ileum.
Sleisenger and Fordtran 11e Ch 116; ECCO UC Guidelines 2022; AGA Guidelines on UC 2020
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