Kidney Ultrasonography After First Febrile Urinary Tract Infection in Children: A Systematic Review and Meta-analysis.

IMPORTANCE: Controversy exists on the clinical utility of kidney ultrasonography after first febrile urinary tract infection (UTI), and clinical practice guideline recommendations vary.

OBJECTIVE: To determine the prevalence of urinary tract abnormalities detected on kidney ultrasonography after the first febrile UTI in children.

DATA SOURCES: The MEDLINE, EMBASE, CINAHL, PsycINFO, and Cochrane Central Register of Controlled Trials databases were searched for articles published from January 1, 2000, to September 20, 2022.

STUDY SELECTION: Studies of children with first febrile UTI reporting kidney ultrasonography findings.

DATA EXTRACTION AND SYNTHESIS: Two reviewers independently screened titles, abstracts, and full texts for eligibility. Study characteristics and outcomes were extracted from each article. Data on the prevalence of kidney ultrasonography abnormalities were pooled using a random-effects model.

MAIN OUTCOMES AND MEASURES: The primary outcome was prevalence of urinary tract abnormalities and clinically important abnormalities (those that changed clinical management) detected on kidney ultrasonography. Secondary outcomes included the urinary tract abnormalities detected, surgical intervention, health care utilization, and parent-reported outcomes.

RESULTS: Twenty-nine studies were included, with a total of 9170 children. Of the 27 studies that reported participant sex, the median percentage of males was 60% (range, 11%-80%). The prevalence of abnormalities detected on renal ultrasonography was 22.1% (95% CI, 16.8-27.9; I2 = 98%; 29 studies, all ages) and 21.9% (95% CI, 14.7-30.1; I2 = 98%; 15 studies, age <24 months). The prevalence of clinically important abnormalities was 3.1% (95% CI, 0.3-8.1; I2 = 96%; 8 studies, all ages) and 4.5% (95% CI, 0.5-12.0; I2 = 97%; 5 studies, age <24 months). Study recruitment bias was associated with a higher prevalence of abnormalities. The most common findings detected were hydronephrosis, pelviectasis, and dilated ureter. Urinary tract obstruction was identified in 0.4% (95% CI, 0.1-0.8; I2 = 59%; 12 studies), and surgical intervention occurred in 1.4% (95% CI, 0.5-2.7; I2 = 85%; 13 studies). One study reported health care utilization. No study reported parent-reported outcomes.

CONCLUSIONS AND RELEVANCE: Results suggest that 1 in 4 to 5 children with first febrile UTI will have a urinary tract abnormality detected on kidney ultrasonography and 1 in 32 will have an abnormality that changes clinical management. Given the considerable study heterogeneity and lack of comprehensive outcome measurement, well-designed prospective longitudinal studies are needed to fully evaluate the clinical utility of kidney ultrasonography after first febrile UTI.