Urinary tract infection and vesicoureteral reflux in children with mild antenatal hydronephrosis.
OBJECTIVE
The postnatal management of mild antenatal hydronephrosis (ANH) remains controversial. The purpose of this study was to evaluate the incidence of UTI and VUR in children with mild ANH in order to determine the necessity of antibiotic prophylaxis (ABP) and VCUG.


METHOD
The data of 1511 patients with various grades of ANH who were referred to Department of Urology, Boston Children's Hospital between January 1998 and January 2010 were reviewed and 760 patients who had mild ANH were identified. The inclusion criteria were: 1) A confirmed report of ANH or actual prenatal ultrasound (US) images. 2) Postnatal evaluation and management conducted at the hospital. 3) Persistent mild hydronephrosis on the first US done between two weeks and three months of age. 4) No other US findings such as ureteral dilatation, duplication anomalies or bladder abnormalities. 5) At least one three-month follow up. Univariate statistical analysis was performed using a Student's t test.


RESULTS
Of the 760 patients who were identified, 608 (80%) were males, and 225 (30%) had bilateral mild hydronephrosis. Of these, 475 patients (63%) underwent an initial screening VCUG. VUR was identified in 13 patients (1.7%) with grades varying from 1 to 5. At follow up, hydronephrosis resolved in 67% of the renal units and worsened in 3.3%. Among the 692 patients with available follow-up data, 23 (3.3%) had a documented UTI. Twelve of these children had an initial screening VCUG that was negative for VUR. Of these 12 patients, seven underwent a subsequent RNC with none having VUR; five of the 12 patients did not undergo a repeat evaluation for VUR (four had a UTI after the screening VCUG and one had an afebrile UTI). Eleven of the 23 children with mild ANH did not have an initial screening VCUG, and all underwent a subsequent VCUG/RNC. Only two children were then found to have VUR Grade 4-5.


CONCLUSION
The incidence of UTI and VUR in children with mild ANH is low. Consequently, routine VCUG screening for VUR and the use of long-term ABP is not necessary for all patients with asymptomatic mild AHN. Evaluation for VUR in children with mild ANH should be reserved for those who subsequently present with a UTI.