MILD PYELECTASIS ASCERTAINED WITH PRENATAL ULTRASONOGRAPHY IS PEDIATRICALLY SIGNIFICANT

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 abse nce of a concomitant anomaly, mild pyelectasis is usually regarded as benign and of no clinical consequence, and follow-up is often not obta ined after the initial ascertainment. To test this, we investigated th e relationship between mild pyelectasis and (1) progression to hydrone phrosis; (2) postnatal vesicoureteral reflux (VUR); and (3) postnatal surgery. Between 1 January 1992 and 1 January 1995, we performed 453 p renatal sonographic examinations of 306 patients with mild fetal pyele ctasis and no other anomalies. During the course of a routine sonograp hic examination, we performed a detailed evaluation of the fetal genit ourinary tract. Mild pyelectasis was defined as a pelvocalyceal fluid- filled space with the smallest of two transverse perpendicular sonogra phic measurements of greater than or equal to 4mm and < 10 mm. Hydrone phrosis was defined similarly, but with a measurement of greater than or equal to 10 mm. Postnatal urological assessment was obtained with r outine renal ultrasonography, and voiding cystourethrography (VCUG), m easurement of Tc-99m-labelled diethylenetriamine pentaacetic acid (DPT A) mercaptacetyltriglycerine (MAG(3)), and intravenous pyelogram, as n ecessary. After exclusion criteria were applied, 294 (96%) patients wi th isolated fetal pyelectasis were considered. A total of 251 (82%) of these were followed with ultrasonography prenatally and during the po stnatal period. Two or more prenatal examinations were carried out in 129 patients (51%) and in 35 (27%) of these cases the biometry progres sed to frank hydronephrosis (> 10 mm). In only six (5%) of the cases f ollowed 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. O n 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 tes t) were found to have an abnormal finding. Whereas the prenatal appear ance 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 prena tal pyelectasis. Although postnatal surgery was necessary in only a sm all number of cases, surgical intervention was necessary in 33% (four of 12) of those with VUR.