Chylous ascites is ascitic fluid with a milky appearance that is rich in triglycerides. The disorder is rare, with a reported frequency of 1 in 20 000 hospital admissions. The most common cause is an intra-abdominal malignancy, usually advanced gastric or pancreatic cancer. The typical mechanism involves obstruction or malignant infiltration of lymphatic channels with the subsequent development of a lymphatic fistula that communicates with the peritoneal cavity. Non-malignant causes of chylous ascites include cirrhosis, tuberculosis, filariasis, abdominal trauma, abdominal surgery and abdominal irradiation. In cirrhosis, the mechanism for chylous ascites might involve increases in lymphatic flow leading to increases in pressure and the rupture of small lymphatic channels. The investigations illustrated below were from a 60-year-old woman who presented with epigastric pain, abdominal fullness and weight loss. She had hepatitis C and had previously had a cholecystectomy. A computed tomography scan showed ascites and a mass near the hilum of the liver consistent with cholangiocarcinoma. An ascitic tap revealed milky fluid with a triglyceride level of 285 mg/dL (3.2 mmol/L). Ascitic fluid cytology was positive for malignant cells. Her serum triglyceride level was 60 mg/dL (0.7 mmol/L) and she had an elevated serum concentration of the tumor marker, Ca19.9. An upper gastrointestinal endoscopy showed multiple white dots in the second part of the duodenum (Fig. 1). Histological evaluation of duodenal biopsies revealed mild inflammation and dilated submucosal lymphatics. A lymphangiogram was performed by injecting 99mTc-labeled human serum albumin into both feet. At 10 min, the label was detected in the mid-abdomen (anterior and posterior views) and, at 4 h, there was partial obstruction of abdominal lymphatic channels (Fig. 2). Some of the label leaked into the peritoneal cavity and was subsequently absorbed into the general circulation. An autopsy at 5 months after the initial presentation confirmed the presence of widespread cholangiocarcinoma.