Background: Almost all newborns have phimosis, which is known as one of the risk factors for urinary infection. The present study analyzed which specific prepuce conditions correlated with the development of febrile urinary infection in Japanese male infants.

Methods: The subjects consisted of 100 children, 64 boys and 36 girls, with febrile urinary infection. Prepuces were classified by their retractability in the male patients and in 714 healthy boys.

Results: Ninety–four percent of first febrile urinary infections occurred before 7 months of age in boys, whereas only 37% of the girls had first infections by that age. The prepuce covered the external urethral meatus in 96% of the healthy boys aged 3 years or less. A gentle retraction maneuver could not uncover the urethral meatus in approximately 40% of the boys aged 0–6 months. The frequency started to decline spontaneously after that age. Male patients aged 0–6 months significantly more often had tightly covered meatus than did healthy neonates (85%vs 42%, P < 0.0001).

Conclusions: These findings indicate that it is specifically those boys whose external urethral meatus are tightly covered with foreskin who constitute the high–risk group for urinary infection. Awareness of this observation should help with diagnosing and managing urinary infection in young boys.