Cautionary tale of how sodium polystyrene sulfonate caused gut necrosis: a case report

Hyperkalaemia is defined as having a serum potassium of equal to or greater than 5.5mmol/L. Six out of 100 people have hyperkalaemia,¹ with an incidence rate of one new case per 100 person-years.² Since two-thirds of hyperkalaemia occurred in the community,² most of them were managed by primary care providers.

Cation exchange resin (CER) is one of a few medical approaches in managing patients with hyperkalaemia. In New Zealand, one of the two choices of CER is sodium polystyrene sulfonate (SPS). As SPS goes through the intestine, the negative sulfonate ion exchanges its sodium with the higher affinity, positively charged potassium ion. The potassium-bound resin is then excreted via faeces, which results in the reduction of total body potassium. Resins have high water-binding capacity, causing constipation by dehydrating the faeces. Hence, co-administration of laxatives is advised.

While effective, administering CER carries a risk of adverse effects. Here, we present a case report involving a patient who developed significant complications as a result of CER use.

Case presentation

A female patient in her 70s presented with a 1-day history of bowel obstruction. She had a surgical background of low anterior resection with loop ileostomy performed 5 months prior for diverticular disease. Her medical background included intermittent hyperkalaemia without any evident renal disease; this was medically managed with 15g of SPS 3 times daily for 1 week per month, repeated over 3 consecutive months in the community. A computed tomography (CT) scan of her abdomen and pelvis indicated mechanical small bowel obstruction, likely of adhesional aetiology.

Initial management was conservative, consisting of nasogastric tube decompression and Gastrografin challenge. She subsequently required operative management for failure to progress and underwent laparotomy and adhesiolysis. This was a challenging operation noting dense inflammatory adhesions resulting in appendicectomy and ileal segmental resections.

On post-operative day 7, the presence of enteric contents in the drain prompted a repeat CT scan showing perforation of the small bowel. Consequently, she presented for a re-look, finding further patchy necrotic small bowel, which was resected.

View Figure 1.

The result was unfortunately 70cm of the functional small bowel. She required multidisciplinary care for short bowel syndrome, reliant on parenteral nutrition. Histological examination of tissues showed ischaemic necrosis, secondary to SPS resin, evidenced by the presence of numerous intramural resin crystals (see Figure 1).

Discussion

CER is commonly prescribed in both the inpatient and outpatient settings for hyperkalaemia management. The estimated incidence of gastrointestinal necrosis after CER administration ranges from 0.14 to 1.8%.^3–5

CER has been shown to injure the mucosa of the gastrointestinal tract.^6–8 Resin crystals may become embedded into the mucosa, causing localised inflammation and subsequent transmural perforation. Patients would often present with either intra-abdominal sepsis or bowel obstruction. There are no known risk factors increasing susceptibility to CER-induced gut necrosis. The mortality rate of CER-induced gut necrosis is estimated to be around 33%.⁹ Those who survive unfortunately suffer from high morbidity burden. Given the severity of this adverse reaction, this patient’s complication has been escalated through appropriate reporting channels. In this patient, with a Naranjo criteria score of 6 (Appendix Table 1),¹⁰ it is likely that SPS resin was the cause of her recurrent bowel necrosis.

This case highlights a serious complication in an everyday medication. It serves as a warning to suspect CER-induced ulcerative or ischaemic enterocolitis in patients presenting with an acute abdomen who have been given CER. Hence, CER should only be used in conjunction with other hyperkalaemia therapies.

Ethics

This study has received approval from the Health New Zealand Research Authorisation under the approval code of SRAF-2026-00039.

View Appendix.