Mild pyelectasis ascertained with prenatal ultrasonography is pediatrically significant

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Abstract
Isolated ‘mild renal collecting system dilatation’ (mild pyelectasis) is a common prenatal sonographic finding. An association between mild pyelectasis and fetal aneuploidy has been established, but in the absence of a concomitant anomaly, mild pyelectasis is usually regarded as benign and of no clinical consequence, and, follow‐up is often not obtained after the initial ascertainment. To test this, we investigated the relationship between mild pyelectasis and (1) progression to hydronephrosis; (2) postnatal vesicoureteral reflux (VUR.); and (3) postnatal surgery.Between 1 January 1992 and 1 January 1995, we performed 453 prenatal sonographic examinations of 306 patients with mild fetal pyelectasis and no other anomalies. During the course of a routine sonographic examination, we performed a detailed evaluation of the fetal genitourinary tract. Mild pyelectasis was defined as a pelvocalyceal fluid‐filled space with the smallest of two transverse perpendicular sonographic measurements of ≥ 4 mm and < 10 mm. Hydronephrosis was defined similarly, but with a measurement of ≥ 10 mm. Postnatal urological assessment was obtained with routine renal ultrasonography, and voiding cystourethrography (VCUG), measurement of 99mTc‐labelled diethylenetriamine pentaacetic acid (DPTA) mercaptacetyltriglycerine (MAG3), and intravenous pyelogram, as necessary.After exclusion criteria were applied, 294 (96%) patients with isolated fetal pyelectasis were considered. A total of 251 (82%) of these were followed with ultrasonography prenatally and during the postnatal period. Two or more prenatal examinations were carried out in 129 patients (51%) and in 35 (27%) of these cases the biometry progressed to frank hydronephrosis (> 10 mm). In only six (5%) of the cases followed prenatally did the measurement diminish to < 4 mm. We found a greater variability in prenatal renal biometry throughout gestation in infants found to have VUR, when compared with those who had no VUR. On postnatal follow‐up, 84 patients had VCUG. Sixteen of these patients (6% of all patients [16/251] and 19% [16/84] of those who had the test) were found to have an abnormal finding.Whereas the prenatal appearance of mild pyelectasis improved in only a small number of cases, we found that it progressed to hydronephrosis in 27% of cases. Postnatal evaluation found VUR to be common in apparent uncomplicated mild prenatal pyelectasis. Although postnatal surgery was necessary in only a small number of cases, surgical intervention was necessary in 33% (four of 12) of those with VUR. Copyright © 1997 International Society of Ultrasound in Obstetrics and Gynecology

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