A 28-year-old woman from Delhi presents with a 6-month history of bloody diarrhea (8–10 stools/day), left lower abdominal pain, and tenesmus. She has lost 4 kg. On examination, she is afebrile, BP 110/70 mmHg, and has mild left lower quadrant tenderness. Colonoscopy reveals continuous mucosal inflammation, friability, and ulceration limited to the colon, with rectal involvement. Biopsy shows crypt distortion and crypt abscess formation. What is the most likely diagnosis?

Explanation

## Diagnosis: Ulcerative Colitis ### Clinical Presentation This patient presents with the classic triad of ulcerative colitis (UC): 1. Bloody diarrhea with frequent stools 2. Continuous left lower abdominal pain and tenesmus 3. Constitutional symptoms (weight loss) ### Endoscopic Findings **Key Point:** The colonoscopic appearance is pathognomonic for UC: - **Continuous mucosal inflammation** (no skip lesions) - **Friability and ulceration** - **Rectal involvement** (always present in UC) - **Limited to the colon** (does not extend beyond the ileocecal valve) ### Histopathological Features **High-Yield:** The biopsy findings confirm UC: - Crypt distortion - Crypt abscess formation - Mucosal and submucosal inflammation - ~~Transmural involvement~~ (this is Crohn disease) - ~~Granulomas~~ (absent in UC; present in ~30% of Crohn disease) ### Differential Features: UC vs Crohn Disease | Feature | Ulcerative Colitis | Crohn Disease | | --- | --- | --- | | **Distribution** | Continuous, colon only | Skip lesions, any part of GI tract | | **Depth** | Mucosal/submucosal | Transmural | | **Rectal involvement** | Always | Variable | | **Fistulas/strictures** | Absent | Common | | **Granulomas** | Absent | ~30% | | **Bloody stools** | Common | Less common | **Clinical Pearl:** Rectal involvement is a hallmark of UC; its absence should prompt consideration of Crohn disease. ### Why Not the Other Options? **Infectious colitis (Shigella):** Would show acute inflammation without crypt distortion; no chronic changes; self-limited course; stool culture/PCR would be positive. **Irritable bowel syndrome:** No mucosal inflammation, ulceration, or histologic changes; colonoscopy is normal; no weight loss or systemic features. [cite:Harrison 21e Ch 297]