Key Takeaways
- Clinical Bottom Line
- Iatrogenic Pharmacological Colitis
Clinical Bottom Line
| Offending Agent | Primary Medical Indication | Endoscopic Presentation |
|---|---|---|
| Sevelamer (Renvela) | Non-calcium phosphate binder for chronic kidney disease (CKD). | “Fish-scale” or rusty, brown crystalline deposits firmly embedded in mucosal ulcerations. |
| Kayexalate (SPS) | Treatment of profound hyperkalemia. | Induces massive, ischemic intestinal necrosis (Kayexalate-induced colonic necrosis). |
Iatrogenic Pharmacological Colitis
While Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are the most notorious pharmacological agents for inducing gastrointestinal ulceration, endoscopists must maintain a high index of suspicion for specialized crystal-induced mucosal injuries, particularly in the nephrology cohort.
The Sevelamer Signature
Sevelamer is a widely prescribed resin used to control serum phosphorus levels in dialysis patients. Because it is a non-absorbable polymer, it transits the entire GI tract intact. In a subset of patients, the drug physically precipitates into sharp, two-toned “fish-scale” crystals that physically embed into the mucosal wall of the stomach or colon. This mechanically induces severe focal ulcerations, ischemia, and chronic pseudopolyps. The endoscopic visual is frequently misinterpreted as a standard inflammatory or infectious colitis until the pathologist expressly identifies the pathognomonic broad, overlapping crystalline structures within the biopsy specimens.
Clinical guidelines summarized by the Gastroscholar Research Team. Last updated: 2026. This article is intended for physicians.
