Pathogenesis of ascites in mice with peritoneal carcinomatosis.

For clarification of the mechanisms underlying formation of malignant ascites, alterations in lymphatic transport from the peritoneal cavity and in peritoneal capillary permeability to protein were studied sequentially in mice inoculated ip with Ehrlich-Lettre ascites tumor cells. All animals developed detectable ascites within 5-7 days of the injection. Diaphragmatic and retrosternal lymph vessels became radiopaque within 30 hours of the ip injection of radiopaque contrast material in control animals without ascites and in 12 experimental mice receiving contrast material 1-3 days after injection of tumor cells. No lymph vessels were opacified in 3 of 4 animals when contrast material was injected on day 5 or in any animal receiving contrast material on or after day 7 following the tumor cell injection. We determined alterations in peritoneal capillary permeability in the second group by measuring the concentration of iv injected Evans blue dye in eluates of sections of peritoneum and contiguous underlying tissue removed 3 hours after injection of dye. Permeability averaged 1.5 times normal (P = 0.02) by day 3 after tumor cell injection, 2 times normal by day 5, and 3 times normal by day 7; it remained at the final level. Although lymph drainage became impaired within 24 hours of the detection of ascites, a progressive increase in capillary permeability began 2 days earlier and was probably the predominant alteration in pathogenesis of the effusion.