Embryology, Kidney, Bladder, and Ureter

The development of the urinary tract begins with the formation of the nephrogenic cord in week four, along which the pronephros, mesonephros and metanephros form. Although the metanephric kidneys act as functional excretory units as early as week eleven, nephrogenesis is not complete until week thirty-two when multiple branching events have formed one to three million collecting tubules. Complex orchestrated interactions between various embryonic tissues, the mesonephric duct, ureteric bud, and metanephric blastema ensure the correct development of the urinary tract. Disruptions to these intricate signaling pathways, either genetic or environmental, result in congenital abnormalities of the kidney and urinary tract (CAKUT) including renal agenesis and dysplasia, multicystic dysplastic kidney disease and polycystic kidney disease.