Ectopic budding of the ureter from the Wolffian duct is the first ontogenic misstep that leads to many-if not all-congenital anomalies of the kidney and urinary tract (CAKUT). The ectopia results in hypoplastic kidney, ectopia of ureterovesical orifice, urinary outflow obstruction and/or reflux. Studies in several mutant mouse models have verified that ectopic ureteric budding indeed precedes formation of CAKUT. Often, the genes involved in navigating ureteric budding to the correct site also regulate later ontogenic events of the kidney and urinary tract. The wide spectrum of CAKUT, for example, multicystic dysplastic kidney, megaureter and atretic ureter, portray the additional important functions of these same genes that are activated at multiple sites and stages during the normal morphogenesis of the kidney and urinary tract

Ectopia of the initial ureter is the first ontogenic mis-step that leads to many congenital anomalies of the kidney and urinary tract (CAKUT). The ectopia results in hypoplastic kidney, ectopia of the ureteral orifice, urinary outflow obstruction and/or reflux. Recent studies on several mutant mouse models verified that ectopic ureteral budding indeed occurs prior to the formation of CAKUT. Often, the genes involved in navigating the site of ureteral budding also regulate later ontogenic processes of the kidney and other urinary tract systems. These additional functions of the genes underlie the wide spectrum of CAKUT, as the genes are expressed at multiple sites at multiple ontogenic stages, and regulate the morphogenesis of the many portions of the excretory system through their distinctive cellular functions.

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