Renal medullary lymphatics: microradiographic, light, and electron microscopic studies in pigs.

Although renal cortical lymphatics have been extensively studied, the existence of renal medullary lymphatics has not been well documented. We studied renal microlymphatics in pig kidneys by retrograde ureteral injection of barium-sulfate-gelatin-saline mixture. Lymphatics filled as a result of forniceal rupture and interstitial extravasation. Microradiographs were correlated with histology and electron microscopy. We traced renal microlymphatic vessels from the arcuate level not only into the cortex but also into the pyramidal region, and therefore concluded that medullary lymphatics existed.