<p><strong>Importance: </strong>Existing data regarding the association between delayed initiation of antimicrobial therapy and the development of renal scarring are inconsistent.</p>

<p><strong>Objective: </strong>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.</p>

<p><strong>Design, Setting, and Participants: </strong>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.</p>

<p><strong>Exposure: </strong>Duration of the child's fever prior to initiation of antimicrobial therapy for the index UTI.</p>

<p><strong>Main Outcomes and Measures: </strong>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.</p>

<p><strong>Results: </strong>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.</p>

<p><strong>Conclusions and Relevance: </strong>Delay in treatment of febrile UTIs and permanent renal scarring are associated. In febrile children, clinicians should not delay testing for UTI.</p>

<p><strong>BACKGROUND: </strong>No studies have examined whether use of sedation during a Tc-99 m dimercaptosuccinic acid (DMSA) renal scan reduces patient discomfort.</p>

<p><strong>OBJECTIVE: </strong>To compare discomfort level during a DMSA scan to the discomfort level during other frequently performed uroradiologic tests, and to determine whether use of sedation during a DMSA scan modifies the level of discomfort.</p>

<p><strong>MATERIALS AND METHODS: </strong>We examined the discomfort level in 798 children enrolled in the Randomized Intervention for children with Vesicoureteral Reflux (RIVUR) and Careful Urinary Tract Infection Evaluation (CUTIE) studies by asking parents to rate their child's discomfort level with each procedure on a scale from 0 to 10. We compared discomfort during the DMSA scan and the DMSA image quality between centers in which sedation was used &gt;90% of the time (sedation centers), centers in which sedation was used &lt;10% of the time (non-sedation centers), and centers in which sedation was used on a case-by-case basis (selective centers).</p>

<p><strong>RESULTS: </strong>Mean discomfort level was highest for voiding cystourethrogram (6.4), followed by DMSA (4.0), followed by ultrasound (2.4; P&lt;0.0001). Mean discomfort level during the DMSA scan was significantly higher at non-sedation centers than at selective centers (P&lt;0.001). No difference was apparent in discomfort level during the DMSA scan between sedation centers and selective centers (P=0.12), or between the sedation centers and non-sedation centers (P=0.80). There were no differences in the proportion with uninterpretable DMSA scans according to sedation use.</p>

<p><strong>CONCLUSION: </strong>Selective use of sedation in children 12-36&nbsp;months of age can reduce the discomfort level experienced during a DMSA scan.</p>