The risk factors of recurrent urinary tract infection in infants with normal urinary systems.

Urinary tract infection (UTI) frequently recurs and increases the risk of renal scarring even in infants with normal urinary tracts. Our study was aimed to find preventive measures for recurrent UTI in these infants. One-hundred ninety infants, who were diagnosed with their first febrile UTI and were proven to have normal urinary systems, were enrolled. We investigated the incidence of recurrent UTI during the following year and the following risk factors: gender, young age, phimosis, vaginal reflux, and acute pyelonephritis (APN) diagnosed by 99m-technetium dimercaptosuccinic acid ((99m)Tc-DMSA)(+) scintigraphy. The incidence of recurrent UTI was 21.1%. The difference in recurrence rate according to gender was not significant. The recurrence rate in infants less than 6 months of age was 25.8%, which was significantly higher than the 7.7% in older infants (P = 0.045). In male infants with persistent non-retractile prepuces, recurrent UTI developed in 34.0%, which was significantly higher than the 17.6% in male infants with retractile prepuces (P = 0.022). The presence of APN in male infants increased the likelihood of recurrent UTI when analyzed by multivariate logistic regression [odds ratio 4.6, 95% confidence interval (95% CI) 1.6-13.0, P = 0.003]. The presence of vaginal reflux and APN in female infants gave no significant difference to the incidence of recurrent UTI. In infants with normal urinary systems, age less than 6 months, non-retractile prepuces and APN in male infants, were the most important risk factors for recurrent UTIs. It is suggested that non-retractile prepuces should be adequately treated to become retractile in young male infants with APN.