ANTENATAL RENAL PELVIS DILATATION - A PREDICTOR OF VESICOURETERAL REFLUX

OBJECTIVE. The purpose of our study was to evaluate the role of antena tally diagnosed renal pelvis dilatation (RPD) as a predictor of vesico ureteral reflux (VUR) in infants. SUBJECTS AND METHODS. All cases of R PD (i.e., those with a renal pelvis diameter equal to or greater than 5 mm) detected on routine antenatal sonography at our institution over a 3-year period were followed throughout infancy with serial sonograp hic evaluation. Infants with moderate to severe RPD on the initial pos tnatal study (i.e., those with a renal pelvis diameter greater than 15 mm) were further evaluated with voiding cystography or nuclear scinti graphy (Tc-99m-2,3-dimercaptosuccinic acid or Tc-99m-benzoylmercaptoac etyltriglycerine). We have now reviewed all postnatal imaging on these infants. In addition, the records of all infants who presented to our institution with clinically symptomatic VUR during this same period h ave been retrieved. Antenatal sonograms were available for review in m ost of these cases. RESULTS. Seventy-six cases of RPD were detected on antenatal sonography at our institution over a 3-year period. Eight c ases were lost to follow-up in early infancy. The remaining 68 infants had serial sonography performed throughout infancy. Twenty-five infan ts showed no evidence of urinary tract dilatation on postnatal sonogra phy. Extrarenal pelves were present in eight cases, and 35 infants had moderate to severe RPD at 72 hr. On further evaluation of this last g roup with voiding cystography or nuclear scintigraphy, diagnoses were VUR (n = 6), pelvic-ureteric junction obstruction (n = 5), renal dyspl asia (n = 1), and congenital megaureter (n = 1). VUR was detected in f ive male infants and one female infant. Twenty-two infants with modera te to severe RPD had neither an obstructive uropathy nor VUR. During t his same period (July 1988-June 1991), 20 cases of VUR were detected a t our institution. Antenatal sonograms were available for review in 16 of these cases. These showed evidence of RPD in five fetuses, whereas the remaining 11 antenatal studies were unremarkable. Our results sho w the positive predictive value of RPD for VUR to be 17%. CONCLUSION. Antenatally detected RPD, in isolation, is a weak predictor of VUR. Po stnatal sonographic evaluation is, however, important in this group. F urther investigation of infants showing moderate to severe RPD in the neonatal period is merited, as such investigation will lead to early d etection of VUR in a significant number of cases (17% of RPD).