Design: Randomised controlled trial.

Allocation: Computer-generated permuted block stratified randomisation done by a centralised data-coordinating centre.

Blinding: Caregivers as well as physicians were blinded.

Study question

Setting: Nineteen sites in a variety of clinical settings in the USA.

Patients: Six hundred and seven children, 2–71 months old, with vesicoureteral reflux (VUR) grades I–IV, recruited after their first or second urinary tract infection (UTI).

Intervention: Patients received either 3 mg/kg trimethoprim plus 15 mg/kg of sulfamethoxazole daily or an identical placebo.

Outcomes: Primary outcomes were febrile or symptomatic recurrence of UTI. Urinary samples were collected by catheterisation, suprapubic aspiration, or clean catch. Secondary outcomes were renal scarring diagnosed by DMSA, antibiotic resistance, and a composite outcome of treatment …