Design: Systematic review and diagnostic accuracy meta-analysis (AAP technical report)
Population: 90 studies of children after first or recurrent UTI
Primary outcome: Sensitivity and specificity of renal and bladder ultrasound for vesicoureteral reflux
Effect: First UTI: sensitivity 50% (95% CI 42% to 58%), specificity 71% (62% to 78%); recurrent UTI sensitivity 26%

One of the AAP guideline's technical reports pooled 90 diagnostic accuracy studies of renal and bladder ultrasound for detecting vesicoureteral reflux after urinary tract infection, searched to August 2023.

After a first UTI, ultrasound had a pooled sensitivity of 50% and specificity of 71%. For high-grade reflux (grades III to V), sensitivity rose only to 66% and specificity to 77%. After recurrent UTI, sensitivity was 26%. Certainty was low to moderate.

Ultrasound is still useful for finding structural abnormalities such as hydronephrosis or duplex systems. What it cannot do is reassure that reflux is absent. A normal scan after a febrile UTI should not be read as ruling out reflux, and decisions about voiding cystourethrography should be made on the guideline's criteria, not on the ultrasound alone.

Do not use a normal renal ultrasound to rule out vesicoureteral reflux after a febrile UTI.
Use ultrasound to look for structural abnormalities such as hydronephrosis, not as a reflux test.
Consider further evaluation for reflux after a recurrent febrile UTI even with a normal scan.
Explain to parents what a normal scan does and does not exclude.

Why it matters

Many pathways treat a normal ultrasound as reassurance about reflux, which this evidence does not support.

The statistics, in plain English

Sensitivity of 50% means ultrasound flagged only half of children who truly had reflux; after recurrent infection it caught about one in four. Specificity of 71% means nearly a third of children without reflux had an abnormal-looking scan.