Importance: Existing data regarding the association between delayed initiation of antimicrobial therapy and the development of renal scarring are inconsistent.
Objective: To determine whether delay in the initiation of antimicrobial therapy for febrile urinary tract infections (UTIs) is associated with the occurrence and severity of renal scarring.
Design, setting, and participants: Retrospective cohort study that combined data from 2 previously conducted longitudinal studies (the Randomized Intervention for Children With Vesicoureteral Reflux trial and the Careful Urinary Tract Infection Evaluation Study). Children younger than 6 years with a first or second UTI were followed up for 2 years.
Exposure: Duration of the child's fever prior to initiation of antimicrobial therapy for the index UTI.
Main outcomes and measures: New renal scarring defined as the presence of photopenia plus contour change on a late dimercaptosuccinic acid renal scan (obtained at study exit) that was not present on the baseline scan.
Results: Of the 482 children included in the analysis, 434 were female (90%), 375 were white (78%), and 375 had vesicoureteral reflux (78%). The median age was 11 months. A total of 35 children (7.2%) developed new renal scarring. Delay in the initiation of antimicrobial therapy was associated with renal scarring; the median (25th, 75th percentiles) duration of fever prior to initiation of antibiotic therapy in those with and without renal scarring was 72 (30, 120) and 48 (24, 72) hours, respectively (P = .003). Older age (OR, 1.03; 95% CI, 1.01-1.05), Hispanic ethnicity (OR, 5.24; 95% CI, 2.15-12.77), recurrent urinary tract infections (OR, 0.97; 95% CI, 0.27-3.45), and bladder and bowel dysfunction (OR, 6.44; 95% CI, 2.89-14.38) were also associated with new renal scarring. Delay in the initiation of antimicrobial therapy remained significantly associated with renal scarring even after adjusting for these variables.
Conclusions and relevance: Delay in treatment of febrile UTIs and permanent renal scarring are associated. In febrile children, clinicians should not delay testing for UTI.