Renal ultrasound after first febrile urinary tract infection in hospitalized children: The ROUTINE prospective observational study protocol.

BACKGROUND: Urinary tract infection (UTI) is a common reason for hospitalization in young children. American and Canadian guidelines recommend universal renal ultrasound after a first febrile UTI to identify genitourinary abnormalities that require further management, despite limited supporting evidence. The Renal ultrasOund after first febrile Urinary Tract INfEction (ROUTINE) study aims to (a) determine the incidence of clinically important and insignificant genitourinary abnormalities on renal ultrasound, (b) describe the cascade of healthcare interventions following the detection of abnormalities, (c) explore parents' experiences, and (d) identify clinical factors associated with clinically important abnormalities.

METHOD: This multicentre, prospective, observational study with an embedded qualitative component will enroll children <24 months of age hospitalized at 17 children's and community hospitals in Canada and the United States after a first febrile UTI, with 1-year follow-up. The primary outcome is detection of genitourinary abnormalities on renal ultrasound, classified by clinical importance using a standardized system. Secondary outcomes include clinical (recurrent febrile UTI), radiologic (vesicoureteral reflux), healthcare interventions (surgery, antibiotic prophylaxis, imaging, specialist follow-up), and parent-reported outcomes (anxiety, involvement in decision making). Parent experiences will be explored through semistructured interviews. Primary analysis will estimate the incidence of clinically important abnormalities and potential overdiagnosis with 95% confidence intervals (CIs). Secondary analysis will summarize radiologic, clinical, healthcare intervention, and parent-reported outcomes and assess predictors of clinically important abnormalities using multivariable logistic regression.

DISCUSSION: This multicentre prospective study with longitudinal follow-up will generate evidence on the utility of universal renal ultrasound after the first febrile UTI. Findings will inform evidence-based management, shared decision-making, and clinical practice guidelines.