Evaluation of prenatally diagnosed hydronephrosis by morphometric measurements of the kidney.

A large number of hydronephrotic kidneys (108) were diagnosed prenatally in 69 infants between 1987 and 1991 and subsequently confirmed postnatally. Prenatal morphometric measurements were done in order to find reliable parameters for the detection of a group at risk for surgical treatment. A second aim of the study was to describe the natural history and management of hydronephrosis detected prenatally. We devised a classification of postnatal obstructive uropathy using ultrasonography and the renal scan. Accordingly, we classified the patients as having mild, moderate or severe hydronephrosis. A renal pelvic antero-posterior diameter (APD) of 9 mm or more, and a pelvic-to-renal APD ratio of 0.45 before 32 weeks of gestation and 0.52 thereafter, were found to be useful for the detection of severe outcome. Our new parameter, a pelvic-to-renal volume ratio of greater than 0.08, can also be used for this purpose.