Embryologic basis for lower ureteral anomalies: a hypothesis.

A hypothesis for the embryogenesis of lower ureteral anomalies invokes variations in location and number of ureteral buds on the mesonephric duct. Such vagaries determine the length of the common nephric duct and the time of meeting of the ureteral bud (or buds) with the urogenital sinus. These factors in turn affect the density of the mesenchymal tissue and its mass in relation to the adjoining structures and, ultimately, the musculature of the trigone as well as the level of the ureteral hiatus and the musculature of the bladder base. Primary reflux, ureteral ectopy, ureteral duplication, ureterocele, functional ureteral obstruction, and congenital strictures are viewed and possibly explained in the light of the embryonal variations mentioned.