Inflammatory Bowel Disease (IBD)
IBD consists of two distinct idiopathic inflammatory conditions: Crohn’s disease and Ulcerative Colitis. Differentiating between these two is a staple of medical board examinations.
1. Comparative Pathology
| Feature | Crohn Disease | Ulcerative Colitis |
|---|---|---|
| Distribution | Anywhere (mouth to anus); “skip lesions”. | Colon only; continuous starting from the rectum. |
| Inflammation | Transmural (entire wall). | Mucosal and submucosal. |
| Histology | Non-caseating granulomas. | Crypt abscesses; no granulomas. |
| Gross Appearance | “Cobblestone” mucosa, creeping fat. | “Lead pipe” colon (loss of haustra). |
2. Exam Must-Knows
- Extra-intestinal Manifestations: Both are associated with uveitis, erythema nodosum, pyoderma gangrenosum, and ankylosing spondylitis.
- Specific Associations:
- Crohn: Malabsorption (B12/bile salt deficiency), kidney stones (calcium oxalate), fistulas.
- Ulcerative Colitis: Primary Sclerosing Cholangitis (p-ANCA positive), toxic megacolon.
Pathology Board Hint: For board exams, remember: Crohn = Cobblestone, Creeping fat, Caseating (non-caseating) granulomas, Transmural. UC = Ulcerative (continuous), Crypt abscesses, Lead pipe, Primary Sclerosing Cholangitis.