Prenatal diagnosis of urinary tract malformations

Oligohydramnios, abnormal kidneys or an abnormal bladder, separately or in combination, are the usual ultrasonographic signs that call attention to an anomaly of the fetal urinary tract. After briefly outlining the normal anatomic features, the author elaborates on these three major signs and discusses bilateral renal agenesis, paradoxic polyhydramnios, obstructive and nonobstructive hydronephrosis, renal cystic disease and urethral obstruction. Radiologists who perform obstetric ultrasonography must be familiar with the general pathophysiologic principles that pertain to the fetal urinary tract, as well as their ultrasonographic manifestations.