Crohn Disease
Crohn’s disease is a chronic inflammatory bowel disease that can affect any part of the gastrointestinal tract, from the mouth to the anus, and is characterized by transmural inflammation.
1. Pathological Hallmarks
| Finding | Description |
|---|---|
| Skip Lesions | Discontinuous areas of inflammation separated by normal bowel. |
| Non-caseating Granulomas | The hallmark histological finding (present in ~35% of cases). |
| Transmural Inflammation | Affects all layers of the bowel wall, leading to fissures, fistulas, and abscesses. |
| Creeping Fat | Mesenteric fat wraps around the inflamed bowel surface. |
2. Clinical Manifestations
- Right Lower Quadrant (RLQ) Pain: The most common site is the terminal ileum.
- Malabsorption: Specifically, B12 (terminal ileum involvement) and bile acids (leading to steatorrhea).
- Kidney Stones: Increased oxalate absorption (calcium oxalate stones) due to calcium binding with fat in the gut.
- Fistula Formation: Transmural involvement allows for bowel-to-bowel, bowel-to-bladder, or perianal fistulas.
Pathology Board Hint: For board exams, remember that Crohn’s is associated with granulomas and transmural inflammation. If you see a “cobblestone” mucosal appearance and a patient with recurrent right lower quadrant pain and weight loss, prioritize Crohn’s disease over UC.