Effect of Renal Venous Occlusion on Intrarenal Pressure.

Abstract

When the renal vein is completely occluded, the intrarenal pressure increases about 3-fold, being elevated to the simultaneous pressure in the vein on the renal side of the occlusion. Usually this pressure is somewhat less than the simultaneous diastolic blood pressure. When the vein is partially occluded, intrarenal pressure does not change until the simultaneous pressure in the vein on the renal side of the occlusion rises to the original intrarenal pressure. At this point, as the occlusion is increased, the 2 pressures rise together and always have the same value. The hypothesis is proposed that the pressure inside the renal peritubular capillaries, venules, uriniferous tubules and lymphatics is normally just above intrarenal pressure, i.e., at 25 mm. Hg. The authors suppose that just as these vessels leave the renal parenchyma the pressure in them abruptly declines toward zero, and this situation permits reabsorption to take place, freed from the influence of random or pathological fluctuations in vena cava pressure. Oncotic pressures and cellular metabolic processes, therefore, are presumed to be the primary determinants of differential reabsorption.