Colonic Mass Secondary to Sevelamer-Associated Mucosal Injury

In patients with chronic kidney disease, sevelamer is used to treat hyperphosphatemia; the mechanism of action is intestinal binding of phosphate and subsequent fecal clearance. Known gastrointestinal (GI) side effects include nausea, vomiting, diarrhea, dyspepsia, and, more rarely, abdominal pain and constipation.1 A 42-year-old woman with hyperphosphatemia secondary to end-stage renal disease was being treated with 800 mg sevelamer every 8 hours. She presented with left lower quadrant abdominal pain and watery diarrhea. Stool cultures and polymerase chain reaction were negative for Clostridium difficile infection. Esophagogastroduodenoscopy revealed grade D esophagitis (histochemical staining was negative for cytomegalovirus, herpes simplex virus, and sevelamer crystals) and a 3-cm hiatal hernia but was otherwise normal. Colonoscopy showed a 6 cm, fungating, oozing mass in the proximal sigmoid colon with no evidence of obstruction (Figure 1). Biopsy of the mass showed necrotic tissue with bacterial overgrowth. Acid-fast and periodic acid-Schiff stain highlighted eosinophilic fish-scale crystals consistent with sevelamer deposition (Figure 2).2 After sevelamer was discontinued, repeat colonoscopy at 3 months showed normal pink mucosa with healthy blood vessels throughout the entire colon (Figure 3)