Acute renal failure in obstructive jaundice in cholangiocarcinoma. This study was aimed at defining the natural history of renal failure in obstructive jaundice due to cholangiocarcinoma, which is an important health problem in northeastern Thailand. Sixty-four patients among a total of 130 patients with obstructive jaundice secondary to cholangiocarcinoma who developed acute renal failure were studied retrospectively. Analysis was made with respect to clinical features, laboratory findings, and outcome. The development of renal failure before surgery was observed in all patients. It was nonoliguric in 80% and was associated with severe jaundice, gram-negative infection (42%), hypotension (31%), hypoproteinemia (30%), hyponatremia (56%), and hypokalemia (63%). The mean duration of renal failure was 2 weeks. All patients underwent surgery for the relief of jaundice. Seventy-seven percent of the patients survived and had recovery of renal function after the relief of jaundice. Twenty-three percent of the patients died of infection. Clinical data highlight the higher serum bilirubin levels and the frequent occurrence of hyponatremia, hypokalemia, and hypotension in renal failure. Their possible roles in contributing to the development of renal failure are discussed. 