Kayexalate or Kalimate crystals: are they the culprits or the bystanders?

Sodium polystyrene sulfonate (Kayexalate) or its analog calcium polystyrene sulfonate (Kalimate) has long been used to treat hyperkalemia in patients with chronic kidney disease (CKD). Although the side effect was rare, there were many case reports in the literature. Its etiology remains unclear. Lillemoe et al., on five uremic patients who developed catastrophic colonic necrosis that was temporally associated with the use of Kayexalate in sorbitol, contributed to death in four of their patients. They further provided experimental evidence implicating sorbitol as the agent responsible for colonic necrosis in a rat model. In contrast to the results of aforementioned animal study, Ayoub et al., published another experimental study in rats, they demonstrated that sodium polystyrene sulfonate (SPS), not sorbitol, was the main culprit for colonic necrosis. Recently, we encountered three patients who had hyperkalemia and were on Kalimate in water. They underwent colonic and gastric biopsy because of developing gastrointestinal symptoms. Kalimate crystals were found in all biopsy specimen, admixed with inflammatory exudate, or standing along on the mucosa surface, without provoking inflammatory reaction. We reviewed the photographs in the published case reports, they were similar to ours. Therefore, we felt that those crystals were bystanders, not the culprits. We fell that SPS ion-exchange resins, if given in water, appears to be clinically effective and reasonably safe to treat hyperkalemia in patients with CKD.