With the advent of the widespread use of prenatal ultrasound in clinical practice, urologic conditions are being diagnosed in many infants before birth. Because ultrasound is performed so commonly, the impact of these diagnoses has been considerable. It remains unclear however, whether this early diagnosis results in benefit to the neonate or merely increased anxiety over testing. In the majority of cases, the parents can be reassured that postnatal evaluation is all that is needed and that their infant will have a good prognosis.

Urologic anomalies are found in about 0.4% of pregnancies. Of these, hydronephrosis is found in about half (see Chapter 13).

Urologic findings may range from mild hydronephrosis, which is essentially a normal finding, to significant hydronephrosis resulting from any type of obstructive uropathy (see Chapter 13, Figs. 13-1, 13-2, and 13-3). In rare cases, renal tumors or congenital anomalies such as exstrophy and epispadias can be found.

After initial diagnosis, a more extensive ultrasound survey is performed to confirm the diagnosis, look for associated findings, and, in the case of renal anomalies, to monitor the amount of amniotic fluid. In rare cases, some intervention is warranted in utero, for example, aspiration of an enormous cystic mass or in very rare cases, placement of a vesicoamniotic shunt. It is very rarely indicated to deliver the baby early. In the overwhelming majority of cases, no intervention is needed before birth. In most, a postnatal evaluation is recommended. However, the overall benefits of prenatal diagnosis for genitourinary lesions are unproven.

A. Hydronephrosis

Easy diagnosis in utero. The following parameters are important.

1. The amount of amniotic fluid (correlates loosely with renal function).

2. Unilateral or bilateral (unilateral is less concerning due to normal contralateral kidney).

3. Evaluate the amount of hydronephrosis (generally by measuring the anterior posterior [AP] diameter of the renal pelvis). An AP diameter greater than 10 mm of the renal pelvis in the third trimester warrants a postnatal evaluation (see below).