Is sonographically demonstrated mild distal ureteric dilatation predictive of vesicoureteric reflux as seen on micturating cystourethrography?

Background: In most paediatric units, the micturating cystourethrogram (MCU) is the gold standard in the diagnosis of vesicoureteric reflux (VUR). Because of the well-known difficulties associated with MCUs, there is interest in any imaging finding which may be predictive of the absence of VUR with enough confidence to avoid the necessity for an MCU.

Objective: To evaluate whether incorporation of measurement of the internal diameter of the retrovesical ureter into a routine urinary tract US protocol can provide a useful predictor of VUR.

Materials And Methods: The radiology information system at the Royal Alexandra Children's Hospital in Brighton was searched to identify children who had urinary tract US and an MCU within 3 months of each other. This identified 285 renal units in 144 patients. The presence and grade of VUR on the MCU was then compared with the presence or absence of mild-to-moderate distal ureteric dilation, using 3.5 mm as the upppr limit of normal for the retrovesical ureter on US.

Results: A distal ureteric diameter of more than 3.5 mm on US is predictive of VUR with a sensitivity of 0.63 and specificity of 0.78. Figures for dilating VUR (grades 3-5) were 0.78 and 0.77, respectively. The negative predictive value of a ureteric calibre less than 3.5 mm in excluding dilating reflux was 0.96. Interestingly, all three solitary renal units had ureteric diameters of more than 3.5 mm but no VUR.

Conclusions: Absence of distal ureteric dilation on US, on its own, cannot reliably exclude VUR. It does, however, make dilating reflux unlikely. We believe US measurement of the distal ureteric diameter is a useful additional tool in everyday assessment of children who might have reflux.