[Postnatal echography and cystography after prenatal diagnosis of minor dilatation of the kidney pelvis. Prospective study of 89 cases].

We evaluated postnatal management after the prenatal diagnosis of moderate dilatation of the renal pelvis (antero-posterior diameter superior to 1 mm per month of pregnancy and inferior to 15 mm at full term). Eighty-nine neonates who had a moderate dilatation in utero were evaluated by ultrasound and voiding cysto-urethrography. Ultrasound was performed between day 2 and day 7 in 83 cases, after day 7 in 6 cases. Voiding cysto-urethrography was performed during first month in 80 cases, after this period in 9 cases. Sixty-five neonates were shown to have a malformation of the urinary tract: reflux (n = 27), megaureter (n = 20), uretero-pelvic junction obstruction (n = 19), renal duplication (n = 7), posterior urethral valves (n = 2), horseshoe kidney (n = 1), ureteric cyst (n = 1). Reflux which is frequent in neonates with urinary tract infection, is the most frequent cause of moderate dilatation of the fetal renal pelvis. Combination of ultrasound and voiding cysto-urethrography in neonates allows a quick, full diagnosis. It helps rationalize the use of prophylactic antibiotic treatment.