[The dichotomous distribution of the renal calices]

The analysis of the caliceal cavities of 30 pairs of Kidneys shows a dichotomous distribution of two types: cranio-caudal for the major calices, ventro-dorsal for the minor ones. The dichotomous organization does not result from the initial division of the ureteral bud: but it should depend upon the renal arteries growth commanding a new caliceal pattern during the morphogenesis of the Kidney.