Genitourinary Imaging Techniques

In the current era of pediatric uroradiology, use of nuclear medicine, ultrasonography, CT, and MRI has been valuable in the identification and management of genitourinary diseases. The characterization of the renal parenchyma did not occur in the past with retrograde pyelography and was limited with intravenous urography. Excellent information about the renal parenchyma and renal functionis currently attainable with current cross-sectional imagingtechniques that can identify tissue differentiation of lesions, distinguish dilatation of the pelvocalyceal system, and determine margins of the kidney and perirenal space. Invasive angiography is limited in application specifically to vascular diseases, although they are uncommon in childhood. Because of these newer techniques, intravenous urography has lost its position as the ‘‘cornerstone’’ of urinary tract imaging and is used mainly to identify pathologic conditions of the ureters. The indications for imaging usually depend on the presentation and age of the patient. In neonates the most common indication for an imaging procedure is the follow-up of an abnormality detected during prenatal sonography. Box 1 lists the more common imaging indications in neonates. The upper urinary tract and bladder can be visualized with sonography at 15 weeks’ gestation; the pelvis and corticomedullary differentiation is readily identifiable after 20 weeks’ of gestation. Newer transducers applied transrectally or transvaginally demonstrate these normal structures earlier and with better resolution. Prenatal identification of congenital renal abnormalities is not unusual because the incidence of congenital urinary tract abnormality is 2 per 1000 live births. The most common diagnosed abnormality in utero is an enlarged collecting system. Identifying