Four hour voiding observation study in infants with posterior urethral valves

Posterior urethral valves (PUV) are often associated with bladder dysfunction. Our primary aim was to investigate bladder status following primary valves resection to gather evidence of function and to guide early clinical management.

Between July 2015-2020, we prospectively evaluated bladder function of PUV infants. Primary outcomes measured were number of voids, voided volume (VV), post-void residual (PVR) and bladder capacity (BC). Statistical comparisons and descriptive analysis were carried out between groups using 2-tails T test and Chi square test using an IBM SPSS Statistics program version 25.

Sixty-one infants were included. Median age at resection was 28 days (5 days-11 months). In thirty-eight patients (62%) diagnosis was suspected antenatally. Vesico-ureteric reflux (VUR) was present in 16 (26%). The 4-h observational study was performed at median 4 days following primary cold-knife valve resection and 1 day (range from 1 to 12 days) after catheter removal. Infants voided an average 6 times (2-13 voids). Bladder capacity was large in 20 (33%) and small in 4 (6.5%) patients with a median ratio BC/eBC = 1.2 (0.49-22.6). Median residual urine was 9 mls but with great variability among the cohort (0-121 mls). A big variability in bladder emptying was noted between patients and between voids performed in one patient. In 13 infants (21%) average PVR was larger than the average voided volume. In 26 (42.6%) PVR was larger than VV at least once. Thirty-eight infants (62.3%) emptied their bladders almost completely at least once (with PVR <5 mls). No difference was found in PVR, Median BC/EBC and PVR/BC between infants with and without VUR (p = 0.654, P: 0.594 and p = 00.481, respectively).

We presented our experience of non-invasive bladder function assessment in infants affected by PUV following primary valve resection. An interesting data is the great variability identified both between patients and between voids performed in a single patient. Average number of voids was similar to the voiding pattern in healthy newborns what reported by Gladh but variability was greater. We observed up to 13 voids in some infants and we can speculate this could reflect the presence of an overactive bladder. We observed at least 1 complete emptying in only 62% of infants and 21% of the cohort had PVR bigger than VV. In almost half of the infants (42.6%) PVR was larger than VV at least once.

Around 40% of infants affected by PUV have abnormal bladder capacity and almost half of them have significant post void residuals following primary resection. Although controversies and limitations are present, we believe that this non-invasive study can provide valuable information to understand the dynamic of the bladder, particularly in children affected by PUV and allow early intervention in children considered "at risk". Having a non invasive way of assessing can help tailor intervention and be useful for future research into early bladder intervention and improving outcomes.