Crohn's Disease vs Ulcerative Colitis: High-Yield Robbins Comparison
High-Yield Clinical Pearls & Exam Keys
Crohn's Disease is transmural (can cause fistulas, strictures, and fissures), whereas Ulcerative Colitis is mucosal & submucosal.
Non-caseating granulomas are pathognomonic for Crohn's Disease (found in ~35% of biopsy specimens). They are NEVER seen in UC.
Ulcerative Colitis always starts in the rectum and spreads contiguously proximal without skip lesions; Crohn's disease exhibits 'Skip lesions' predominantly at the terminal ileum.
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Crohn's Disease Macroscopic Clues
Skip lesions with cobblestone mucosal appearance
Creeping fat on serosal surface
Transmural inflammation leading to strictures ('String sign of Kantor')
Diagnostic Matrix: Crohn's Disease vs Ulcerative Colitis
| Feature | Crohn's Disease | Ulcerative Colitis |
|---|---|---|
| Site of Involvement | Any part of GI tract (Mouth to Anus); Terminal Ileum most common | Limited to Colon & Rectum (Rectum always involved) |
| Distribution Pattern | Skip lesions (Discontinuous) | Continuous & Contiguous from rectum upwards |
| Depth of Inflammation | Transmural (All layers involved) | Mucosa and Submucosa only (Superficial) |
| Granulomas | Non-caseating granulomas present (~35%) | Absent |
| Complications | Strictures, Bowel obstruction, Fistulas, Perianal fissures | Toxic Megacolon, Massive Hemorrhage, Higher risk of Colorectal Carcinoma |
| Radiology (Barium) | String sign of Kantor (narrowed ileum), Cobblestoning | Lead-pipe appearance (loss of haustrations), Collar-button ulcers |
| Smoking Correlation | Smoking increases risk & worsens flares | Smoking is strangely protective / ceases symptoms |
| Serological Marker | ASCA positive (Anti-Saccharomyces cerevisiae) | p-ANCA positive (Perinuclear ANCA) |
Interactive Clinical Vignette Practice
Live Rule-Out EngineA 26-year-old female presents with recurrent crampy right lower quadrant pain, low-grade fever, and weight loss. Colonoscopy reveals discrete linear ulcers separated by normal mucosa in the ileocecal region. Biopsy of an ulcer base reveals non-caseating epithelioid granulomas. The diagnosis is:
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