Risk of urinary tract infection in patients with hydroureter: An analysis from the Society of Fetal Urology Prenatal Hydronephrosis Registry

Background: Prenatal hydronephrosis is one of the most common anomalies detected on prenatal ultrasonography. Patients with prenatal hydronephrosis and ureteral dilation are at increased risk of urinary tract infection (UTI) and continuous antibiotic prophylaxis (CAP) is recommended. However, current guidelines do not define the minimum ureteral diameter that would be considered a dilated ureter in these patients.

Objective: We evaluate the definition of clinically relevant hydroureter, its association with UTI, and the impact of CAP.

Study design: Patients with prenatal hydronephrosis from seven centers were enrolled into the Society for Fetal Urology Prenatal Hydronephrosis Registry from 2008 to 2020. Patients with ureteral measurement on ultrasound were included. Patients with ureterocele, ectopic ureter, neurogenic bladder, posterior urethral valves, horseshoe or solitary kidney, known ureteropelvic junction obstruction, or follow-up less than one month were excluded. Primary outcome was UTI. Analyses were performed using Cox regression.

Results: Of the 1406 patients enrolled in the registry, 237 were included. Seventy-six percent were male, ureteral diameter ranged from 1 to 34 mm, and median follow-up was 2.2 years. Patients with ureters 7 mm or greater had nearly three times the risk of UTI adjusting for sex, circumcision status, antibiotic prophylaxis and hydronephrosis grade (HR = 2.7, 95% CI: 1.1-6.5, p = 0.03; Figure). In patients who underwent voiding cystourethrogram (VCUG; 200/237), ureteral dilation of 7 mm or more identified patients at increased UTI risk controlling for sex, circumcision status, vesicoureteral reflux and hydronephrosis grade (HR = 2.3, 95% CI: 0.97-5.6, p = 0.06). CAP was significantly protective against UTI (HR = 0.50 (95% CI: 0.28-0.87), p = 0.01). Among patients who underwent VCUG and did not have vesicoureteral reflux, ureteral dilation 7 mm or greater corresponded with higher UTI risk compared to ureteral diameter less than 7 mm on multivariable analysis (HR = 4.6, 95% CI: 1.1-19.5, p = 0.04).

Conclusions: This is the first prospectively collected, multicenter study to demonstrate that hydroureter 7 mm or greater identifies a high-risk group for UTI who benefit from antibiotic prophylaxis. In contrast, patients with prenatal hydronephrosis and non-refluxing hydroureter less than 7 mm may be managed more conservatively.