Hypothesis / aims of study
To evaluate a novel transpubic sonography approach to assess functional voiding in asymptomatic women. This study aimed to: (i) assess the inter- and intra-tester and test- retest reliability of measures obtained during imaging of functional voiding; and (ii) provide normative data of measurements of bladder and bladder neck displacement, urethral diameter changes, and urethral movement during functional voiding; and (iii) calculate displacement of pelvic floor landmarks during muscle contractions using the new technique.
Study design, materials and methods
This observational / validation study included asymptomatic women evaluated with real-time transpubic ultrasound imaging and concurrent uroflowmetry during functional voiding. Imaging was performed using a GE S8 ultrasound machine (and curved array C1-5 transducer). Urine flow rate, voiding pattern and volume were assessed using a Uroflow (Laborie).
Thirty-two participants with no history of lower urinary tract dysfunction participated. To record functional voiding, participants sat on an over-toilet seat positioned above the Uroflow device. The sonographer held the covered transducer between the volunteer’s legs over the pubic symphysis and anterior perineum in the sagittal plane. The image orientation and parameters were optimised to enable visualisation of bladder neck, urethral angle, and pelvic floor muscles, with the long axis of the fibrocartilage pubic symphysis maintained ventrally as a reference landmark. The participant was requested to initiate urination until complete bladder emptying. Following bladder emptying, images were recorded while the participant was instructed to; (i) relax the PFMs, (iii) contract the PFMs, and (iii) strain. Ultrasound video data were stored for offline analysis.
For assessment of intra-tester reliability, 32 participants were scanned by sonographer 1 in separate sessions 1 to 2 weeks apart.
For assessment of inter-tester reliability, the same 32 participants were scanned by a second sonographer in session 2 before or after sonographer 1. Sonographers were blinded to each other’s findings.
Measures were made using recommendations from the International Continence Society (1). These are: pubo-urethral angle (degrees); distance (mm) between inferior border of symphysis pubis (SP) and bladder neck (BN), Dx, Dy; pubo-urethral angle of the bladder neck opening; widest AP urethral diameter during max void (mm); BN diameter at max void. Other measures included: full bladder volume measured with both ultrasound and uroflow (ml); urine flow rate, patterns, and volume (ml); longitudinal length of the cartilaginous symphysis pubis (SP).
Results
All participants (n=32) completed the study. Participants had a mean (SD) age of 35(9) years, BMI of 24.2(4.9) kg/m2 and 20(62%) were nulliparous. The mean bladder volume measured with ultrasound and uroflow were 360.4 ml and 461.3 ml respectively. The mean and median SP length was 38.5mm and 38.6mm respectively. The mean pubo-urethral angle was stable at full, max and end void of 120-125 degrees with an increase to 140 (18.5) degrees at straining and reduction to 94 (15.9) degrees during contraction of the pelvic floor. The mean Dx, Dy and SP-BN distances were 12.7mm, 20.9mm and 26.4mm, respectively. The mean (SD, range) for other US measures were SP - 38.5(3.4, 25.3, 47.1) mm, urethral diameter opening during voiding - 5.2 (2.0, 1.60, 10.60) mm and bladder neck diameter - 8.4 (3, 3.2, 18.40) mm
Pubo-urethral angle measures were repeatable. ICC values were 0.87 for intra-tester measures, 0.77 for inter-tester measures and 0.96 for the intra-tester test-retest relationship.
Interpretation of results
The novel transpubic sonography technique enabled real-time evaluation of functional voiding in all participants and these data provide a foundation for assessment of symptomatic patients. Ultrasound measures of bladder volume were less than output recorded with the uroflow. There is a significant difference in BN and urethral diameter compared to flow patterns as seen figure 2.