Deposition of Sevelamer crystals in gastrointestinal tract and lung parenchyma: A rare autopsy finding

Abstract Introduction/Objective Sevelamer carbonate is a non-calcium-based phosphate binder used for the management of hyperphosphatemia in patients with end stage renal disease. The well-known side effects of sevelamer include nausea, vomiting and abdominal pain. However, there are few case reports which described the deposition of sevelamer crystals in the gastrointestinal tract causing mucosal injury, pseudotumor or obstruction. Methods/Case Report We hereby present a case of a 43-year-old decedent female with past medical history of seizures, hypertension, cocaine use, type B aortic dissection status post thoracic endovascular aortic repair, total arch replacement, reconstruction of innominate, carotid, and subclavian artery who presented with hematochezia concerning for possible aorto-esophageal fistula on 10/06/2022 and acute kidney injury. Imaging showed a thrombus in mid-esophagus, blood in trachea and narrowing of the left main stem bronchus. Labs revealed worsening of BUN and creatinine and up trending hyperphosphatemia and therefore sevelamer carbonate via nasogastric route was started on 10/13/22. Unfortunately, the patient’s hospital course was complicated, and she passed away on 11/14/2022. At autopsy, the deceased had gross evidence of acute lung injury with diffuse alveolar hemorrhage, aorta-bronchial ruptured aneurysm defect and aorto-esophageal fistulas. On histopathological examination, the stomach, small and large bowel showed autolysis, necrosis, and numerous rectangular shaped, non-polarizable crystals. The crystals with characteristic morphology of “fish scale” with hues of pink in the center and yellow to orange in the periphery were identified as sevelamer crystals. Interestingly, crystal deposition was also identified in lung parenchyma and rarely in aortic wall and the fistula. Results (if a Case Study enter NA) NA Conclusion As one of the more commonly used resins in end stage kidney disease, gastrointestinal adverse effect of sevelamer carbonate is often underrecognized. Our case report heightens the awareness of the characteristic morphology of this biologically inert agent, sevelamer to those who are unaware of their morphology. This case also highlights the adverse effect of sevelamer in all patients presenting with gastrointestinal symptoms, such as gastrointestinal bleeding and abdominal pain with the use of sevelamer.