Practice guidelines from the American Academy of Pediatrics recommend renal ultrasonography and voiding cystourethrography (VCUG) in all children two months to two years of age with a documented first urinary tract infection (UTI). Other authorities have suggested using renal scanning with technetium 99m at the acute infection and later to detect evidence of renal scarring. Hoberman and colleagues conducted a prospective trial to determine if imaging studies in young children with a first UTI altered management or improved outcomes.

This multicenter trial initially enrolled 421 children who were one to 24 months of age and had a fever and pyuria or bacteriuria in a catheterized urine specimen. Final study results were calculated for 309 children (73 percent), after excluding those with negative urine cultures, declined consent, or other logistical barriers to participation. Each child received renal ultrasonography and technetium 99m renal scanning within 48 hours of the initial diagnosis of UTI. VCUG was performed in 98 percent of the subjects one month after the infection, and follow-up renal scanning was performed in 89 percent of the subjects six months after diagnosis to detect any renal scarring. Children with at least grade II vesicoureteral reflux received either trimethoprim-sulfamethoxazole (TMP-SMX) or nitrofurantoin once daily for 11 months or until the reflux was classified as grade I or less.

The initial renal sonogram was normal in 88 percent of the children with UTI. The presence of hydroureter on ultrasonography was not a sensitive screen for urine reflux, identifying only 10 percent of children who had reflux that was later confirmed by VCUG. No child had a change in clinical management based on renal sonography.

Nuclear medicine renal scanning identified acute pyelonephritis in 61 percent of children with UTI. At six months of follow-up, repeat renal scanning identified scarring in 9.5 percent of children. Scarring was more likely in the subgroups of patients with initial evidence of vesicoureteral reflux (15 percent scar rate) than in those without vesicoureteral reflux (6 percent scar rate). No child with an initially normal renal scan had scarring on the six-month follow-up scan.

VCUG demonstrated reflux of urine in 39 percent of children. Only 4 percent of children had reflux above grade III.

The authors conclude that results of initial renal sonography and nuclear medicine scanning are not likely to alter management in young children with UTI. The authors advocate obtaining a urinalysis and urine culture to identify any recurrence of infection in subsequent febrile episodes in a child with a documented UTI.