Colonic Necrosis Induced by Calcium Polystyrene Sulfonate

phy scan revealed thickening of the right colon wall, no free peritoneal fluid or evidence of pneumoperitoneum. The patient was admitted and 1 day later a colonoscopy was performed, showing a congestive and ulcerated mucosa in the right colon and a deep necrotic ulcer in the cecum, with a diameter of 40 mm (Fig. 1). Taking into account these findings, the main differential diagnosis was either ischemic colitis or infectious colitis. The patient started empiric antibiotic therapy and renal function was stabilized. Pathologic and microbiological examinations excluded infectious colitis, namely tuberculosis, cytomegalovirus or Clostridium difficile colitis. Biopsies from the cecal ulcer revealed necroinflammatory and granulation tissue containing basophilic-stained polystyrene sulfonate crystals (Fig. 2). Thus, the diagnosis of necrosis of the colon induced by CPS was considered. Six days after the admission, the patient experienced worsening of the abdominal pain. An abdominal ultrasound was performed the following day and revealed an abscess adjacent to the ulcer of the cecum (Fig. 3). The abscess may reflect a microperforation of the cecum that could be an iatrogenic event related to the colonoscopy or, less probably, a spontaneous event facilitated by the presence of the large ulcer and transmural necrosis. The microperforation was successfully managed with a single ultrasoundguided needle aspiration of the abscess and with conservative medical treatment. CPS was suspended, the patient started a more restrictive potassium diet, and the hemo