An 80-Year-Old Man With Hematochezia and Hyperkalemia

Abstract

Question: An 80-year-old man with a history of colon cancer with previous resection and a primary anastomosis as well as chronic kidney disease presented to the emergency room with a presyncopal episode. On arrival, he was hypotensive, with a hemoglobin of 9.9 g/dL, blood urea nitrogen of 45 mg/dL, and creatinine of 1.9 mg/dL with a serum potassium of 6.0 mmol/L. The patient’s hyperkalemia was attributed to chronic kidney disease and was managed medically. After treatment for hyperkalemia, on the same day of admission, the patient developed bright red bleeding per rectum. The patient underwent colonoscopy on day 2 of admission, which showed internal hemorrhoids, as well as a dusky appearing mass at the rectosigmoid junction, 13 cm from the anal verge measuring 5 cm in length (Figure A). Biopsies of the mass were obtained, and histologic analysis of the biopsies is shown (Figure B). What is the etiology of these endoscopic and histologic findings? See the Gastroenterology web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI. Histology showed colonic mucosa with ischemic injury, ulceration, acute inflammatory exudates, absence of neoplastic cells, and the presence of sodium polystyrene sulfonate (SPS) crystals (highlighted in the rectangle in Figure B). Immunohistochemical stain for cytomegalovirus was negative (not shown). Upon review of the patient’s medications, 1 dose of SPS (Kayexalate) had been given on the first day of admission before the development of hematochezia. Owing to a suspected sampling error, the patient underwent repeat colonoscopy 5 days after the index endoscopy which showed notable regression of the previously seen pseudotumor (Figure C); biopsies of the remnant lesion showed persistent ischemic type injury with acute inflammatory exudates and SPS crystals (indicated by the blue arrow in Figure D). SPS is a potassium-binding resin used to treat acute hyperkalemia. SPS has been associated with gastrointestinal complications, including ischemic colitis, bleeding, and perforation.1Bui M. Chou S.Y. Faubert P. et al.Resin-induced colonic pseudotumor: rare complication from chronic use of potassium binders in a hemodialysis patient.Case Rep Nephrol. 2016; 20163692086PubMed Google Scholar Ischemic colitis with associated pseudotumor formation is a rare adverse event that can mimic a malignant process, and present as hematochezia or as a radiographically apparent colonic mass.1Bui M. Chou S.Y. Faubert P. et al.Resin-induced colonic pseudotumor: rare complication from chronic use of potassium binders in a hemodialysis patient.Case Rep Nephrol. 2016; 20163692086PubMed Google Scholar These pseudotumors are non-neoplastic, inflammatory, and necrotic lesions that have been reported to occur in the esophagus, colon, and in extraintestinal areas.2Chatila A.T. Bilal M. Merwat S. Kayexalate-induced colonic pseudotumor.Clin Gastroenterol Hepatol. 2019; 17: e73Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar,3Goh L.H. Wong J. Chng T.W. et al.Extra-intestinal sodium polystyrene sulfonate crystal-induced inflammatory pseudotumour in an asymptomatic haemodialysis patient.Int Urol Nephrol. 2021; 53: 1265-1266Crossref PubMed Scopus (1) Google Scholar Although the mechanism is unknown, it is proposed that SPS causes a shift in the osmotic load and, therefore, vascular redirection and then ulceration or ischemia.2Chatila A.T. Bilal M. Merwat S. Kayexalate-induced colonic pseudotumor.Clin Gastroenterol Hepatol. 2019; 17: e73Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar The characteristic pathologic finding includes a fish scale pattern seen on hematoxylin and eosin staining representing SPS crystals. SPS-induced pseudotumor formation does not seem to be dose dependent; investigators have reported the development of SPS-induced ischemic pseudotumor after a wide range of doses, ranging from merely 2 doses to scheduled administration up to 1 year.1Bui M. Chou S.Y. Faubert P. et al.Resin-induced colonic pseudotumor: rare complication from chronic use of potassium binders in a hemodialysis patient.Case Rep Nephrol. 2016; 20163692086PubMed Google Scholar, 2Chatila A.T. Bilal M. Merwat S. Kayexalate-induced colonic pseudotumor.Clin Gastroenterol Hepatol. 2019; 17: e73Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar, 3Goh L.H. Wong J. Chng T.W. et al.Extra-intestinal sodium polystyrene sulfonate crystal-induced inflammatory pseudotumour in an asymptomatic haemodialysis patient.Int Urol Nephrol. 2021; 53: 1265-1266Crossref PubMed Scopus (1) Google Scholar Recognition of this entity is therefore important irrespective of the SPS dose and duration to avoid unnecessary interventions.1Bui M. Chou S.Y. Faubert P. et al.Resin-induced colonic pseudotumor: rare complication from chronic use of potassium binders in a hemodialysis patient.Case Rep Nephrol. 2016; 20163692086PubMed Google Scholar SPS-induced ischemic pseudotumor regresses with discontinuation of the drug. This case highlights the potential for mistaking SPS-induced pseudotumor formation for malignancy. In addition, in the absence of a dose response, a single dose of SPS can lead to the development of ischemic pseudotumor.