O3336: Is there a benefit from continuous prophylactic antibiotics for children with isolated antenatal hydronephrosis?

Background: Isolated hydronephrosis refers to dilatation of the renal pelvis, with no ureter or bladder abnormalities. Current guidelines recommend continuous antibiotic prophylaxis (CAP) for Society for Fetal Urology (SFU) grades 3 and 4 due to the possible increased risk of urinary tract infection (UTI). However, there is a growing global focus on reducing unnecessary antibiotic use due to the rise in antibiotic resistance. Herein, we describe CAP patterns and UTI development in children with isolated hydronephrosis from a large single center experience.

Methods: We reviewed our prospectively maintained antenatal hydronephrosis database from 2015-2025 and included children < 24m at baseline with isolated hydronephrosis. Patients with known vesicoureteral reflux, megaureters, and other congenital abnormalities were excluded, as well as index UTIs (that prompted the diagnosis) and post-instrumentation UTIs. We collected data about sex, circumcision status, degree of hydronephrosis (SFU grade and anteroposterior diameter [APD]) and rates of surgical intervention and UTIs. UTIs were defined as a positive urinalysis for leukocytes and culture >50,000 CFU/L of a single organism in a febrile child with a specimen obtained by catheter or midstream. Breakthrough UTIs are those that occurred while taking CAP.

Results: A total of 799 children with isolated hydronephrosis were included with a median age (IQR) of 2 (1, 4) months at presentation and a follow-up time of 23 (11, 37) months. Most children (81%) were male, of which 64% were uncircumcised, 56% had high grade hydronephrosis and 26% had a pyeloplasty. CAP was prescribed in 49% of children for a median duration of 4 (1, 8) months. Only 14 (2%) children developed a confirmed febrile UTI during surveillance at 5 (2, 11) months of age, of which 5 (36%) were breakthrough. There were no significant differences in the development of UTI between sex, circumcision status, surgery, CAP use or hydronephrosis severity (Table).

Conclusion: The UTI rate in children with isolated hydronephrosis is very low and not impacted by CAP use. Children with isolated hydronephrosis can be safely monitored with ultrasound and it appears that CAP is not required for this population.