When the Crystals Do Not Align: A Rare Case of Sevelamer-Induced Colonic Ulceration and Crystal Deposition

Introduction: Sevelamer is a commonly used non-calcium-based phosphate-binding agent designed to reduce serum phosphate levels in patients with end-stage kidney disease (ESKD). Severe gastrointestinal injury induced by Sevelamer is uncommon but noteworthy. We present a rare case of Sevelamer-induced colonic ulceration with crystal deposition and colitis. Case Description: A 64-year-old male with a history of heart failure with reduced ejection fraction, coronary artery disease, ESKD on intermittent hemodialysis, and a previous cerebrovascular accident was admitted for acute hypoxic respiratory failure and septic shock. His hospital course was complicated by atrial flutter, which required a heparin drip that was discontinued after he developed melena with severe anemia. A gastroenterology consultation led to a colonoscopy with biopsy, which revealed a fragment of granulation tissue with ulceration containing Sevelamer crystals consistent with Sevelamer-induced colitis. There were no chronic ischemic changes in the intact colonic mucosa, suggesting the possibility of acute ischemia or Sevelamer-related injury. Consequently, Sevelamer was discontinued. Due to the worsening of his comorbid conditions, the patient was transitioned to comfort care, and dialysis was withdrawn. Discussion: Crystal deposition by ion-exchange resins like Sevelamer can result in inflammation, mucosal damage, and ulceration. While Sevelamer is generally well tolerated while causing mild gastrointestinal side effects such as nausea, vomiting, constipation, flatulence, and diarrhea, cases of more severe gastrointestinal mucosal injury have been associated with its use. Albeit rare, Sevelamer-induced colitis should be included in the differential diagnosis of gastrointestinal bleeding in patients with ESKD. This case contributes to the growing evidence of significant gastrointestinal complications related to Sevelamer.