A Case of Yellow Granuloma Appendicitis with Calcium Polystyrene Sulfonate Deposition

Abstract

A 72-year-old man with chronic renal failure caused by underlying diabetic nephropathy and a single kidney (after right kidney removal) was being monitored in the Department of Nephrology. For hyperkalemia associated with these conditions, he was taking calcium polystyrene sulfonate (CPS) regularly. The patient noticed that his stool was black and contained blood, and abdominal computed tomography (CT) showed a mass lesion at the tip of the appendix. Abdominal contrast ultrasonography showed a saccular dilatation at the tip of the appendix with a multilocular structure with contrast enhancement of the mucosa. There was no significant uptake in the appendix on positron-emission tomography CT (PET-CT). Myxoma of the appendix was therefore diagnosed, and ileocecal resection was performed. Histopathological examination showed yellow granulomatous changes with CPS crystal deposition in the appendix. This is believed to be the first Japanese report of appendicitis of this histological type. The possibility of CPS-induced yellow granuloma appendicitis should be considered in the diagnosis and treatment of patients taking oral CPS, and it is important to obtain detailed medical and drug histories.