Role of diaphragmatic, visceral, and parietal pathways in peritoneal fluid absorption in rat peritoneal dialysis

Assessment was made of the contribution of lymphatic and nonlymphatic fluid absorption to net fluid loss from the peritoneal cavity. Diaphragmatic, visceral, and parietal pathways in lymphatics and nonlymphatics were examined using a rat model with adhesion of the diaphragm to the liver, evisceration, these two procedures in combination, and without treatment. In each of these cases, six rats were used, each dialyzed for 180 min with Krebs-Ringer solution. The peritoneal net fluid absorption rate (PNFAR) was determined based on the disappearance of 125I-bovine serum albumin (BSA) from the peritoneal cavity and the lymphatic absorption rate (LAR), was based on the appearance of this albumin in the blood. Seventy-eight percent of net fluid loss occurred via the nonlymphatic pathway, primarily through parietal and visceral absorption; and the remaining 22% through the lymphatics, the main pathway being the subdiaphragmatic lymphatics. Nonlymphatic fluid absorption would thus appear to be a major route of fluid loss from the peritoneal cavity in rat peritoneal dialysis.