RENAL LYMPHATIC FUNCTION FOLLOWING VENOUS PRESSURE ELEVATION

Abstract

The renal lymphatic system plays an important role in removing excess fluid from thekidneys. Unfortunately, the factors influencing lymphatic flow are difficult to measure. We used asimple model to represent renal lymphatics as a single pressure source (PL) pushing lymphthrough a single resistance (RL). In anesthetized dogs, we cannulated renal lymphatics andmeasured lymph flow rate (QL) as we varied pressure (PO) at the outflow end of the lymphatics.There was no significant change in QL as we increased PO from -5 to 0 cm H2O. In other words,there was a plateau in the QL vs. PO relationship. At higher PO's, QL decreased linearly withincreases in PO. From this linear relationship, we calculated RL as - PO/ QL and we took PL asthe PO at which QL = 0 µl/min. At baseline, RL = 0.34 ± 0.14 (SD) cm H2O "min/µl and PL = 8.2 ±4.4 cm H2O. When we increased renal venous pressure (PV) from baseline (3.5 ± 3.0 cm H2O),the plateau in the QL vs. PO relationship extended to higher PO's, RL decreased, and PL increased.Renal interstitial fluid volume and interstitial pressure increased following elevation of PV. Theextension of the QL vs. PO plateau with increasing PV suggests that renal interstitial pressure maypartially collapse intrarenal collecting lymphatics which may compromise lymph flow.