[A case of metastatic colorectal cancer suffering from hyperammonemic encephalopathy induced by 5-FU, continuously treated with FOLFOX therapy].

We report a rare case of metastatic colorectal cancer who suffered from hyperammonemic encephalopathy induced by 5- FU and was continuously treated with FOLFOX therapy. A 50-year-old man with ileus was diagnosed with ascending colon cancer Stage IV, and a right hemicolectomy was performed. Postoperative chemotherapy with modified FOLFOX6 was performed. Complications of nausea and vomiting were seen on day 2 , with confusion and cognitive disturbances on day 3 . None of the other radiographic examinations provided an explanation for his symptoms. Laboratory examination revealed hyperammonemia, so branched-chain amino acid solutions and high-volume drip infusion were started for its treatment. His symptoms entirely disappeared on day 4. We changed to chemotherapy for FOLFOX4 using branched-chain amino acid solutions and drip infusion. The tumor marker level normalized following two courses, and CT following ten courses showed that the size of the lung metastasis and abdominal lymph node had reduced significantly. The patient is currently receiving FOLFOX4.