Improving Variations in Bladder Ultrasound Assessment of Post-Void Residual Urine Volume in Moderate Bladder Outlet Obstruction

Abstract

Objectives: This study aimed to assess the accuracy of post-void residual (PVR) urine volume measurements in patients with moderate bladder outlet obstruction.
Materials and Methods: This prospective observational study was conducted between January and December 2019. The inclusion criteria were male patients with symptoms of moderate bladder outlet obstruction. On the other hand, patients with a history of diabetes, symptoms of urinary tract infection, and positive urine for pyuria, as well as patients using medications, such as diuretics, alpha-blockers, and anticholinergic drugs, were excluded. The patients were asked to drink 1000 mL of water one to two hours before the initial ultrasound scan. Pre-void bladder capacity was measured, followed by a post-void ultrasound for residual urine volume measurement at three intervals: immediately after voiding, 15-20 min after the first void, and one week later with an empty bladder. Assessment of per-void capacity was carried out, based on the patient’s subjective sensation of bladder fullness (a strong desire to void).
Results: A total of 78 male patients, with the mean age of 60 years, were included in this study (27 cases in group I; 37 cases in group II; and 14 cases in group III). The mean PVR volume was 92 mL in the first measurement, 62 mL in the second measurement, and 60 mL in the third measurement. Significant differences were found between the first and second PVR measurements and between the first and third PVR measurements (P<0.05). However, no significant difference was found between the second and third PVR measurements (P=0.107). On the other hand, significant differences were found between groups I and II and between groups I and III (P<0.05) in the three PVR measurements. Nevertheless, there was no significant difference between groups II and III in the three PVR measurements (P=0.204, 0.56, and 0.487 for the first, second, and third PVR measurements, respectively).
Conclusion: A bladder ultrasound must be performed and interpreted carefully to avoid further unnecessary medications, investigations, or procedures. We recommend a second PVR measurement in patients with bladder outlet obstruction. Also, it is suggested to conduct similar studies in different conditions to confirm our findings.