[Sensitivity of voiding urosonography as a function of the number of the cyclic bladder fillings]

Vesicoureteral reflux (VUR) can occur intermittently. Cyclic testing of VUR (observation of multiple phases of filling and micturition) increases the detection rate of VUR, as has been shown in studies which have generally used a two-cycle test period.

How large is the dependence of the sensitivity in voiding urosonography (VUS) on the number of observed cycles when more than two cycles are observed in a larger number of patients? How many cycles should be observed in order to achieve sufficient sensitivity?

The study population consisted of 302 patients (225 female, average age 2.5 years [range 1 month-17 years]; 77 male, average age 6 months [range 1 month-2.5 years]) with 607 kidney-ureter units (KUU), examined in a pediatrican practice from 05 January 2016 to 31 December 2019. The examinations were performed by contrast-enhanced color Doppler voiding urosonography using the ultrasound contrast agent SonoVue® (Bracco Imaging, Milan, Italy) for an average of 3.14 cycles and, in the case of undetectable VUR, for an average of 3.5 cycles (range 1-6 cycles).

In all, 118 of 302 patients were found to have VUR. In terms of KUU, 163 of 607 KUU exhibited reflux. VUR occurred intermittently in 32.5% of KUU. Depending on the number of cycles observed, there was a significant increase in sensitivity of the VUS. Using the observation of five cycles as a reference for the sensitivity, the following values are obtained: 1 cycle = 82.2%, 2 cycles = 87.7%, 3 cycles = 96.3%, 4 cycles = 98.8%, 5 cycles = 100%.

To achieve a sensitivity of 96% in detecting VUR, three cycles must be observed. If less than three cycles are observed, the sensitivity shows a marked decrease.