Embryology of the urinary tract and prenatal diagnosis of congenital obstructive anomalies.

: Fetal malformations within the urinary tract are frequently detected during sonographic examination in the second and third trimester of pregnancy. Detection has been facilitated by a continued evolution of new technological equipment and by increased knowledge regarding the existence of direct sonographic patterns (kidneys) and/or indirect sonographic patterns (amniotic fluid volume). A wide range of variability and severity of such malformations has been noted, from the so-called "functional" types which disappear spontaneously after birth, to those requiring postnatal surgery, as well as those with fatal prognosis. Due to the complexity of the embryological development of the fetal urinary system, the pathogenesis of such malformations is still not well known. The main stages of development of the urinary tract in the embryo were studied in 156 cases involving urinary tract obstructions. Follow-up was strictly adhered to until the postnatal outcome. Sonographic patterns representative of this pathology were studied in order to verify if a correct diagnosis and an accurate definition of the prognosis could be arrived at using the data.