Fluorouracil (5-FU) is one of key therapeutic drugs for many solid tumors, including head and neck cancer. Pneumatosis intestinalis and portal venous gas, while being rare adverse effects of 5-FU administration, could prove fatal. Hyperammonemia is also one of the serious adverse effects of 5-FU. Herein, we report the case of a patient with hypopharyngeal cancer who developed both portal venous gas and hyperammonemia during 5-FU chemotherapy.
A 79-year-old man with a few months’ history of difficulty in swallowing was referred to our hospital. Upper gastrointestinal endoscopy and tissue biopsy revealed squamous cell carcinoma and the patient was diagnosed as having locally advanced hypopharyngeal cancer, cT4aN0M0. He was initiated on neoadjuvant chemotherapy with carboplatin (CBDCA) and 5-FU on day 1. On the day 3, he presented with consciousness disturbance and Kussmaul breathing. Upper gastrointestinal endoscopy revealed pneumatosis intestinalis under the gastric mucosa and abdominal computed tomography revealed portal venous gas. At the same time, blood test revealed hyperammonemia. As we considered these events to be serious adverse effects of 5-FU, we discontinued the 5-FU infusion and started the patient on treatment with antibiotics and a proton-pump inhibitor. The general condition of the patient gradually improved under careful observation, and the patient eventually showed complete recovery. In clinical settings, it is important to have a high index of suspicion for serious adverse effects of 5-FU, such as pneumatosis intestinalis, portal venous gas, and hyperammonemia.
