The renal cortical lymphatic system in dogs with unimpeded lymph and urine flow.

The distribution and extent of the lymphatic circulation in the renal cortex was analyzed in three dogs under conditions of unimpeded lymph and urine flow. The kidneys were drip fixed with acrolein in vivo, and cortical tissue strips were prepared for light and electron microscopic examination. Analysis of 90 tissue strips revealed 38 cortical lymphatics, one third of which were intralobular in position. The intralobular lymphatic capillaries were related primarily to tubules, afferent arterioles, or renal corpuscles. The remainder of the lymphatics were located in interlobular connective tissue areas in association with the interlobular blood vessels. Interlobular lymphatics had a surface area twice that of intralobular vessels. Stereological analysis was used to estimate the volume density of the components of the renal cortex. The volume density of lymphatics was found to be 0.0014, but because of the relative infrequency of lymphatics, this value was considered to be approximate. The volume density data for non-lymphatic renal components were found to be in close agreement with published data. From these volume density values it was concluded that the volume of cortical lymph in a functioning dog kidney is equivalent to about 1% of the volume of blood in the cortical peritubular capillaries.