Objectives: 1. To assess the reproducibility of an electronic ultrasonographic technique for the measurement of urethral angulation; 2. to test the ability of measurement of the urethral angle and bladder neck mobility to predict genuine stress incontinence; 3. to compare ultrasound variables in stress incontinent women and in controls.
Design: Case-control study.
Population: Twenty-three incontinent women and 50 controls.
Methods: Electronic measurements of the distance between the bladder neck and the symphysis pubis, the bladder neck and the symphysis pubis line and the midline of the symphysis (alpha angle) and the angle between the proximal and distal urethra (beta angle) by means of perineal ultrasonography with a comfortably full bladder at rest, during the Valsalva manoeuvre and during maximal pelvic floor contraction. The same procedure was performed by a second investigator. Repeatability was evaluated by the technique described by Bland and Altman. Statistical analysis was performed using Student's t test and the two-tailed paired t test.
Main outcome measures: To test the possible role of the urethral angle in maintaining female continence.
Results: Ultrasound analysis showed good repeatability between the two observers and is not influenced by vesical volume. Beta angle and urethrovesical mobility are inversely proportional, both in continent and in incontinent women. Urethral angle identifies genuine stress incontinence better than urethrovesical mobility (sensitivity 96% vs 87%; specificity 92% vs 68%; positive predictive value 85% vs 55%). There are significant differences in all ultrasound variables between incontinent women and continent controls.
Conclusions: This study suggests a significant role of the urethral angle in maintaining female continence (in incontinent women it is lower at rest and lowers with straining). Measurement of the urethral angle can provide useful additional information to that provided by ultrasound evaluation of bladder neck mobility.