Clinical implications of genitourinary embryology

This review focuses on recent advances in molecular embryology of the upper and lower urinary tract with an emphasis on clinical correlation in order to gain a better understanding for the mechanism of congenital anomalies.Normal morphogenesis of the kidney, ureteral bud differentiation, ureteropelvic junction formation, and bladder and trigone development are regulated by complex epithelial-mesenchymal signaling events. Failure of these signaling events to occur at specified times results in developmental anomalies. Immunohistochemical staining using animal and human tissues provides insights into the timing of various signaling events during development. Murine knockout models examine the role of various signaling molecules in genitourinary organogenesis. Lineage studies map the fate of cells in developing genitourinary tissues. Some of the most important findings include the role of bone morphogenetic protein-4 in morphogenesis of the kidney, the importance of the mesenchyme associated with the proximal and distal segments of the ureter in directing differentiation, the role of bone morphogenetic protein-4 signaling in smooth muscle formation at the ureteropelvic junction, and the predominant contribution of bladder smooth muscle in forming the trigone.Recent studies have begun to unravel the complex molecular and cellular mechanisms for many common congenital anomalies of the genitourinary tract. A more precise understanding of these developmental events may provide insights into normal and abnormal development.