Colonic Mass Secondary to Sevelamer-associated Rectal Ulcer

The phosphorous balance is clinically important in increasing the long-term outcomes and preventing complications of end-stage renal disease. Sevelamer is a phosphate binder used widely to regulate hyperphosphatemia. On the other hand, gastrointestinal side effects increase with increasing sevelamer intake. A 29-year-old male with end-stage renal disease of IgA nephropathy on maintenance hemodialysis was admitted for diffuse alveolar bleeding and pneumonia. He presented with a low-grade fever and watery diarrhea tinged with blood. Initially, a Clostridioides difficile-associated diarrhea treatment was started with positive findings of Clostridioides difficile toxin and culture. Despite this, there was no improvement in the symptoms even with the appropriate antibiotic treatment. Computed tomography of the abdomen and pelvis revealed an occlusive mass in the rectum and secondary obstructive changes in the sigmoid colon. The initial suspicion was a malignancy or fungal infection. Sigmoidoscopy with a biopsy identified the mass as a lump of mucous material with the entire lumen covered with exudate. The subsequent histopathology examination revealed a colonic mucosal injury and characteristic ''fish scale"-like sevelamer crystals in the exudate. The diagnosis of a sevelamer-induced rectal ulcer was made. We report this case of a sevelamer-associated rectal ulcer of the sigmoid.