The kidneys are given to Venus in the western scheme, the reasoning being that they are paired and balanced, that they regulate the fluids and salts of the body, and that they lie in the region of the loins governed by Venus-ruled Libra. In the Chinese scheme the kidney, shen, belongs to the water phase, is paired with the bladder, stores the jing or essence inherited at conception and expended through life, governs birth, growth, reproduction and ageing, produces marrow and fills the brain, and is associated with fear and with the ears. The Chinese kidney is thus far more than a filtering organ; it is closer to a theory of constitutional vitality, and the mismatch with the anatomical kidney is one of the standard difficulties in translating Chinese medical texts.
Ayurveda treats the kidneys, vrikka, as principally governed by Apana Vata, the downward-moving vata subtype seated in the pelvis that governs the elimination of urine as well as of stool and the processes of menstruation and childbirth. Hebrew tradition gives the kidneys, kelayot, a role distinct from both: in the Psalms and in Jeremiah God is repeatedly described as the one who tries or tests the heart and the reins, an old English word for kidneys, treating the organ as an inward seat of conscience and hidden intention that only God can examine, a moral rather than a medical or elemental reading of the pair.
Sources Christian AstrologyWilliam Lilly with The Roots of Ayurveda: Selections from Sanskrit Medical WritingsDominik Wujastyk