Does duration of voiding abstinence with bladder ultrasound and uroflowmetry affect bladder emptying?.

Introduction & Objectives: A full bladder is required for adequate assessment on bladder ultrasound. However, over-distension may lead to impaired detrusor contraction and bladder emptying. Our departmental uroflowmetry requires patients to abstain from voiding for 2 h, compared to 1 h with bladder ultrasound. We aim to evaluate and assess the relationship between duration of voiding abstinence and bladder emptying. Method(s): Retrospective data collection for patients who presented to our Victorian metropolitan hospital for a uroflowmetry assessment between January 2016 and January 2017 was performed. Patients are included in the study if a bladder ultrasound was performed within 6 months of uroflowmetry. Voided volume (VV) and post-void residuals (PVR) between the 2 modalities were compared, while prostate size was also recorded for all men included in the study. Result(s): 59 patients who met inclusion criteria were included in this study (58 males, 1 female). The mean age was 65 years of age (range 20-88). The mean prostate volume was 51.3 ml. The mean Qmax for the uroflow was 11.8 ml/s. The mean initial bladder volume with uroflowmetry was 220.5 ml, compared to 237 ml with ultrasound. PVR with uroflowmetry was 86.4 ml compared to 76.7 ml with ultrasound. T-test did not reveal any statistical significance between the 2 modalities. Conclusion(s): Our study did not demonstrate any effect of duration of voiding abstinence on bladder emptying. There was also no difference in the mean initial volume between the two different modalities. This seems to correlate well with the PVR volumes, which indicates that even 2 h of voiding abstinence is probably not enough to cause over-distention and impaired detrusor contraction. From our study, we conclude that it is not necessary to ask patients to abstain from voiding for 2 h for all bladder ultrasounds. Further prospective studies should be performed however to determine whether this finding can be extrapolated to include a