[A Case of Hyperammonemia Induced by 5‒FU in a Patient with Advanced Rectal Cancer].

A 74‒year‒old male was diagnosed with advanced rectal cancer with bowel obstruction, and abscess formation. After sigmoid colostomy, FOLFOXIRI plus bevacizumab as preoperative chemotherapy was initiated. On day 3, during continuous administration of 5‒fluorouracil(5‒FU), the patient developed impaired consciousness accompanied by convulsive seizures and conjugate deviation. Electroencephalography(EEG)revealed no epileptic discharges, and imaging studies revealed no abnormality. A blood test showed a high ammonia level of 367μmol/L. In the absence of prior liver disease, the cause was suspected to be due to high‒dose 5‒FU. Administration of lactulose was started. The ammonia level normalized and the consciousness recovered quickly by the following day. It was thought that chemotherapy would be difficult to continue, and 1 month later, robot‒assisted low anterior resection and ileostomy were performed. The patient was discharged home without complication on postoperative day 13. We report this case of advanced rectal cancer in which administration of high‒dose 5‒FU caused hyperammonemia accompanied by impaired consciousness, with a literature review.