S1747 An Unusual Suspect: Sevelamer Induced Ischemic Colitis

Abstract

Introduction: Renal failure is associated with a host of electrolyte imbalances of which hyperphosphatemia is an important complication. Sevelamer is a phosphate binder used to help excrete excess phosphate in feces in patients with end stage renal disease. Though rarely reported, sevelamer administration has been associated with the development of ischemic colitis. We present the case of a 57yo male who presented with right lower quadrant pain and was subsequently diagnosed with right sided ischemic colitis associated with sevelamer administration. Case Description/Methods: A 57yo male with a past medical history significant for end stage renal disease on dialysis, end stage heart disease with left ventricular assist device on coumadin, morbid obesity, type 2 diabetes mellitus and a surgical history significant for remote appendectomy and partial sigmoid colon resection presented in the setting of weeklong unremitting and sharp right lower quadrant abdominal pain. At presentation, the patient was hemodynamically stable. Laboratory evaluation was significant for a WBC of 15.72 109/L, hemoglobin of 10.2 g/dl , platelets 210 109/L. Electrolytes were within normal limits, BUN 39 mg/dL, creatinine 7.93 mg/dL, and LDH 141 U/L. CT abdomen and pelvis with contrast was concerning for colitis involving the cecum and proximal ascending colon [Figure 1]. Colonoscopy revealed cecal mucosa grossly consistent with ischemic colitis [Figure 1]. Biopsies of the affected area identified ischemic-like changes with the presence of sevelamer crystals [Figure 1]. Follow up CT angiogram ruled out mesenteric ischemia. Further review of the patient’s medications revealed that the patient was on sevelamer therapy and it was subsequently discontinued. Discussion: Sevelamer is a rare nidus for gastrointestinal lesions first described in 2008. Most commonly, lesions present as erosions and ulcerations or pseudo inflammatory polyps with a predisposition for the colon. Histological findings involve crystal identification inside mucosa or around epithelial surface in irregular shapes with a broad and curved mosaic pattern described as “fish scale”. On H&E staining, the crystals appear two toned with bright pink linear accentuations and rusty yellow background. It is believed that diabetic patients and those with chronic constipation are more likely to be at risk for sevelamer toxicity as slower colonic transit time increases the risk for the sevelamer crystals, excreted in feces, to develop crystalline concretions.Figure 1.: A). Endoscopic image of eight-centimeter polyp in situ B). Endoscopic image showing encapsulation of polyp via snare C). Endoscopic image demonstrating scar after polypectomy D). Resected eight-centimeter polyp Figure 2. E) and F). Transverse and coronal sections of the CT scan of the abdomen/pelvis demonstrating a 3-cm focal enhancing lesion at the junction of the descending and sigmoid colon with associated intussusception.