Lessons of the month 3: Duodenal perforation after polystyrene sulfonate.

Ion-exchange resins, sodium or calcium polystyrene sulfonate, are commonly used medications for management of hyperkalaemia. However, the drug can be associated with serious bowel injury. We report a case of a renal transplant recipient who developed duodenal ulcer perforation secondary to the use of calcium polystyrene sulfonate. Characteristic eosinophilic non-polarisable rhomboid shaped crystals were evident in the affected area of ulceration on histologic examination in addition to features of cytomegalovirus inclusions. We also hypothesised that gastroparesis secondary to autonomic dysfunction could have led to prolonged luminal contact time with polystyrene, further predisposing to bowel injury. © Royal College of Physicians 2020. All rights reserved.