Objective: To investigate whether the sphincter area in women can be seen and quantified with intra-urethral ultrasound (IUUS). Currently, sphincter capacity in women is determined by clinical tests, vaginal palpation, urodynamics and urethral pressure profile.
Patients and methods: A pilot study using IUUS was carried out in 32 stress incontinent and 12 healthy women to enable the urethra and para-urethral tissue to be visualized. Round-tipped miniature transducer-containing (20 MHz) catheters (6 and 9 F) were tested. Both provided 15 frames per second. Real-time 360 degrees cross-sectional ultrasound images were obtained by using a standard intraluminal ultrasound system. The external urethral sphincter was visualized and its circumference and area were measured.
Results: IUUS provided high resolution imaging of the urethra and surrounding tissues. The whole length of the urethra was visualized. The external sphincter was easily recognized as an oval-shaped, hypoechoic structure. Examination of 44 stress incontinent and healthy women revealed a negative correlation between the external urethral sphincter (area and circumference) and the grade of stress incontinence (P < 0.01). In no patient with normal urinary continence was the sphincter reduced in size (< 2.8 cm circumference).
Conclusion: IUUS is a useful technique in the diagnosis of incontinence, as conventional methods provide little information on the sphincter itself. The evaluation of sphincter size and morphology could help in the choice of therapy.