Ascites dynamics in cirrhosis. Proposal and validation of a methylene blue dilution test

In order to investigate ascites dynamics, we examined a simple compartmental model based on the analysis of the peritoneal clearance rate of methylene blue in 58 patients with cirrhosis and ascites. After abdominal injection of 10-50 mg methylene blue, the ascitic concentration of the dye progressively decreased, following an exponential trend. The dye distribution volume (7.1 + 0.61, mean + SE) and its peritoneal clearance (87.6 + 5.0 ml/min) were determined by mathematical analysis. The accuracy of volume determinations was controlled in 5 subjects by total paracenteses. In 6 patients, methylene blue clearances were also compared with free-water peritoneal clearances, estimated by a deuterium oxide dilution technique. The decrease in the ascitic concentrations of both tracers followed a corresponding exponential decay in all patients, and the parameters of ascites dynamics determined by the two techniques (peritoneal volumes and clearance values) showed no statistical difference. We therefore suggest the use of the methylene blue dilution test to estimate free-water transperitoneal dynamics, which may be useful in the evaluation and control of cirrhotic patients with ascites.