A 71-year-old man developed hepatic portal venous gas (HPVG) while receiving carboplatin and paclitaxel; constipation due to morphine was also considered to have contributed.The man, who had stage IV non-small cell lung cancer, began receiving zoledronic acid and a time-released formulation of morphine [dosage and route not stated] to treat bone metastases and associated pain. After starting morphine, he developed a side-effect of ileus-like severe constipation [duration of treatment to reaction onset not stated]. He also received chemotherapy consisting of carboplatin and paclitaxel [dosages and routes not stated]. On day 29 of chemotherapy, he developed a slight pain in his upper abdomen and abdominal fullness. He also had symptoms relating to chemotherapy, including nausea, appetite loss and decreased physical activity. Ultrasonography revealed hyperechoic fine particles in the portal vein, and an abdominal CT revealed gas in the peripheral part of his liver. He was diagnosed with HPVG. He had a strong desire to defecate, and after defecation, his abdominal symptoms markedly improved.The man received a nasogastric tube and antibacterials, while oral intake of food or liquid was prohibited. The following day, his abdominal pain almost completely resolved, and subsequent CT and ultrasound imaging revealed complete resolution of gas in the liver. Chemotherapy with carboplatin and paclitaxel was withdrawn, and pemetrexed was started; HPVG did not recur.Author comment: "[W]e speculate that chemotherapy agents, severe constipation caused by the effect of opiate analgesic, and the decreased physical activity (an adverse effect of chemotherapy) worked cooperatively as the causes of HPVG in the present case. Constipation was considered to have played an especially important role in the development of HPVG in our case." Sakamoto A, et al. Hepatic portal venous gas in a patient undergoing chemotherapy for non-small cell lung cancer.