A 28-year-old woman from Delhi presents with a 6-month history of bloody diarrhoea, abdominal cramping, and weight loss of 4 kg. She reports 6–8 stools per day with blood and mucus. On examination, she is afebrile, has mild left lower quadrant tenderness, and no perianal findings. Laboratory investigations show haemoglobin 9.2 g/dL, albumin 3.1 g/dL, and elevated CRP. Colonoscopy reveals continuous inflammation limited to the colon with friable, granular mucosa and crypt abscesses on histology. No skip lesions are identified. What is the most likely diagnosis?

Explanation

## Diagnosis: Ulcerative Colitis ### Clinical Presentation **Key Point:** Ulcerative colitis (UC) presents with bloody diarrhoea, abdominal pain, and systemic features (anaemia, hypoalbuminaemia, elevated inflammatory markers). This patient's 6-month history of mucopurulent bloody stools with constitutional symptoms is typical of UC. The absence of perianal disease and the continuous nature of inflammation are hallmark features. ### Endoscopic & Histological Findings | Feature | Ulcerative Colitis | Crohn Disease | |---------|-------------------|----------------| | **Distribution** | Continuous, colon only | Skip lesions, any part of GI tract | | **Depth** | Mucosa + submucosa | Transmural | | **Crypt changes** | Crypt abscesses, distortion | Granulomas (non-caseating) | | **Perianal disease** | Absent | Present (fistulas, skin tags) | | **Cobblestoning** | Absent | Present | **High-Yield:** UC is always confined to the colon and rectum; involvement is continuous without skip lesions. Crypt abscesses are characteristic. ### Pathological Hallmarks 1. **Mucosal inflammation** — limited to mucosa and submucosa (not transmural) 2. **Crypt abscesses** — neutrophil infiltration into crypts 3. **Crypt distortion** — loss of normal architecture 4. **Continuous distribution** — no skip lesions 5. **Absence of granulomas** — distinguishes from Crohn disease **Clinical Pearl:** The presence of crypt abscesses on histology is a key diagnostic criterion for UC; granulomas would suggest Crohn disease instead. ### Why This Patient Has UC, Not Crohn Disease - **Continuous inflammation** (not patchy/skip lesions) - **Colon-only involvement** (Crohn can affect any part of GI tract) - **No perianal disease** (common in Crohn) - **Crypt abscesses** (UC hallmark; Crohn has non-caseating granulomas) [cite:Robbins 10e Ch 17]