Colon Necrosis Due to Sodium Polystyrene Sulfonate with and without Sorbitol: An Experimental Study in Rats

Abstract

Introduction: Based on a single rat study by Lillemoe et al, the consensus has been formed to implicate sorbitol rather than sodium polystyrene sulfonate (SPS) as the culprit for colon necrosis in humans treated with SPS and sorbitol. We tested the hypothesis that colon necrosis by sorbitol in the experiment was due to the high osmolality and volume of sorbitol rather than its chemical nature.

Methods: 26 rats underwent 5/6 nephrectomy. They were divided into 6 groups and given enema solutions under anesthesia (normal saline, 33% sorbitol, 33% mannitol, SPS in 33% sorbitol, SPS in normal saline, and SPS in distilled water). They were sacrificed after 48 hours of enema administration or earlier if they were very sick. The gross appearance of the colon was visually inspected, and then sliced colon tissues were examined under light microscopy.

Results: 1 rat from the sorbitol and 1 from the mannitol group had foci of ischemic colonic changes. The rats receiving SPS enema, in sorbitol, normal saline, distilled water, had crystal deposition with colonic necrosis and mucosal erosion. All the rats not given SPS survived until sacrificed at 48 h whereas 11 of 13 rats that received SPS in sorbitol, normal saline or distilled water died or were clearly dying and sacrificed sooner. There was no difference between sorbitol and mannitol when given without SPS.

Conclusions: In a surgical uremic rat model, SPS enema given alone or with sorbitol or mannitol seemed to cause colon necrosis and high mortality rate, whereas 33% sorbitol without SPS did not.

Fig 1. Pathologic findings of rats’ colon with the different enema solutions.

Fig 1a: Control rats with distal colon showing preserved crypt architecture and minimal inflammation. Fig 1b: Sorbitol (33%) with transmural necrosis showing trans-mural necrosis. Fig 1c: Mannitol (33%) with transmural ischemia. Fig 1d: SPS with sorbitol (33%) showing transmural infarction with crystal deposition. Fig 1e: SPS with normal saline with trans-mural ischemia and crystal deposition. Fig 1f: SPS with water showing sub-mucosal edema and crystal deposition in the serosa with accompanying acute inflammation. Hematoxylin-Eosin of cross-section of rat colons: images on the left panel (Fig 1a-f) represent original magnifications x40; images on the right panel (Fig 1a-f) represent original magnifications x200. Black arrows indicate magnified area.