Urinary Reflux Screening in Infants with Prenatal Hydronephrosis

Abstract

Source: Szmanski KM, Al-Said AN, Pippi Salle JL, et al. Do infants with prenatal hydronephrosis benefit from screening for vesicoureteral reflux? J Urol. 2012; 188(2): 576– 581; doi: 10.1016/j. juro.2012.04.017Investigators at Montreal Children’s Hospital sought to determine the necessity of vesicoureteral reflux (VUR) screening in children with prenatally detected hydronephrosis (PHN). They report their experience with consecutive infants seen at their institution with postnatally confirmed PHN from 1998 to 2003. All patients with anatomic abnormalities of the urinary system were excluded from the analysis.At the authors’ institution, some children with low-grade hydronephrosis (grades I and II) underwent screening for VUR with a voiding cystourethrogram (VCUG) while others did not, partly determined by whether they were followed by a urologist or nephrologist. All patients with high-grade hydronephrosis (Grade III or higher) underwent VCUG screening. Medical records of all children with PHN were reviewed for presence of VUR diagnosed by VCUG, circumcision status, gender, exposure to antibiotic prophylaxis, and diagnosis of urinary tract infection (UTI). Children with low-grade PHN were compared to those with high-grade PHN (grades III and IV). The primary outcome measure was development of a symptomatic or febrile UTI, after accounting for gender, circumcision, and VUR.The study included 206 children with PHN, 148 with low-grade hydronephrosis and 58 with high-grade hydronephrosis. Of the 148 infants with low-grade hydronephrosis, 98 (66%) underwent a VCUG. Among the 155 children who underwent VCUG, the overall prevalence of VUR was 11%, and was not statistically different between those in the low-grade PHN group (9%) and those in the high-grade PHN group (14%). No UTIs were noted among patients with grade I hydronephrosis during 53 patient-years of follow-up. The incidence of UTI was 3.6 times higher among the high-grade PHN group (11.1 infections per 100 patient-years) than among the overall low-grade PHN group (3.52 infections per 100 patient-years). In multivariate analysis, UTI was significantly more likely among children with high-grade hydronephrosis than in children with low-grade hydronephrosis after correcting for gender and circumcision status. The association remained strong after also correcting for VUR status but was of borderline statistical significance (P = .053). Gender, circumcision, and VUR on antibiotic prophylaxis were not statistically significant independent risk factors for UTI.The authors conclude that children with low-grade hydronephrosis and anatomically normal upper urinary tracts do not benefit from VCUG screening, since UTI risk appears to be associated with hydronephrosis grade rather than VUR.Dr Shukla has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.PHN is the most common anomaly detected on routine prenatal sonography, seen in 1% to 3% of all pregnancies.1 The standard workup of children with a history of PHN has traditionally included a renal ultrasound and VCUG, but there is lack of consensus as to whether these studies are necessary since controlled trials with appropriately extended postnatal follow-up are lacking. The American Urological Association guidelines, based on a large meta-analysis of available literature, conclude that there is insufficient evidence to accurately assess the risk of UTI in children with a history of PHN, regardless of the presence of VUR.2 The Society of Fetal Urology similarly published a consensus statement recently that does not recommend VCUG as a routine element of the postnatal workup in all children with a history of PHN since the VUR diagnosed in these cases carries a high rate of spontaneous resolution and lower risk of UTI.3It is important to note that the investigators for this study excluded all children with anatomic abnormalities, and, therefore, children with the potential diagnosis of posterior urethral valve, ureterocele, ectopic ureter, or neurogenic bladder, for example, must be carefully investigated and the approach discussed here is not applicable. Many children with these anatomic abnormalities have low-grade or no hydronephrosis.Rigorously differentiating low-grade from high-grade hydronephrosis is a subjective dilemma. As confirmed in this study, children with high-grade hydronephrosis warrant a full evaluation with a postnatal renal ultrasound, VCUG, and perhaps a diuretic nuclear renogram. These children have a much higher risk of developing a UTI, and may also have concurrently high risk for anatomical anomalies.Overall, however, this study confirms a broad trend in pediatric medicine to utilize the VCUG judiciously.