Kinetics of peritoneal fluid absorption in patients with chronic renal failure.

Previous measurements of fluid absorption from the peritoneal cavity were made after a single injection of a protein-bound marker by following changes in the concentration of the marker with time. Absorption of the marker substance itself had to be estimated. The present study measured absorption of peritoneal fluid by more direct methods. 1.5 to 2.1 L of 0.9% saline, along with 10 muCi of RISA were infused into the abdomens of nine chronic renal failure patients through peritoneal dialysis catheters. Initial paritoneal fluid volumes were determined by dilution. After 7 hr, a second dose of RISA (5 muCi) was infused, and volumes in the peritoneal cavity were again determinted by dilution of the increment dose. At 8 hr, an attempt was made to recover the RISA remaining in the peritoneal cavity by draining and repeatedly flushing that space. The amount of RISA recovered was used to calculate independently the amounts of RISA and fluid which had been absorbed during the 8 hr period. There was good agreement between peritoneal fluid volumes calculated at 7 and 8 hr by these and other techniques. By 7 hr, 23.8% +/- 10.9 S.D. of the initial peritoneal fluid volume ahd been absorbed. The amount of RISA absorbed during the same period was 17.3% +/- 4.9 of the initially administered dose. At 7 hr, only 23.7% +/- 6.3 of the absorbed RISA was in the plasma. The proposed techniques of volume measurement are valid and point to great variation among patients in the rate of fluid absorption from the peritoneal cavity.