^ http://purl.obolibrary.org/obo/BTO_0000671

1: One of a pair of vertebrate organs situated in the body cavity near the spinal column that excrete waste products of metabolism, in humans are bean-shaped organs about 4 1/2 inches (11 1/2 centimeters) long lying behind the peritoneum in a mass of fatty tissue, and consist chiefly of nephrons by which urine is secreted, collected, and discharged into a main cavity whence it is conveyed by the ureter to the bladder. 2: Any of various excretory organs of invertebrate animals. [ From_Merriam-Webster's_Online_Dictionary_at_www.Merriam-Webster.com:http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=kidney ]