Urethrometry: Considerations of static, dynamic, and stability characteristics of the female urethra

Measurements of resting anterior/posterior urethral pressures and detrusor function are considered with respect to clinical observations made during the physical examination of patients complaining of urinary incontinence. Observations made on a large number of consecutive unselected patients show that the extent of incontinence is much larger than can be determined by the physical examination alone. Urethral profilometry shows that there are statistically significant differences in the anterior and posterior maximum urethral closure pressure between stress‐ and non‐stress‐incontinent patients regardless of age and detrusor function. The measurement of posterior resting urethral closure pressure correlates best with the physical demonstrability of stress incontinence among patients with a stable detrusor function. The age‐related rate of decrease in the maximum resting urethral pressure is approximately the same for both anterior and posterior urethra in the continent patient. Demonstrably incontinent patients show a rate of posterior urethral pressure decrease with age double that of those with no evidence of incontinence on physical examination. The differences between anterior, posterior, and lateral closure pressures are discussed in terms of their correlative anatomical periurethral structures and are graphically represented in a threedimensional perspective schema. The direction of occlusive forces in the proximal healthy female urethra is critically examined at rest and also during dynamic events such as holding and coughing. The results show that compressive forces in the proximal urethra are asymmetrically distributed with respect to the anterior/posterior plane and are symmetrical in the lateral plane. Resting urethral pressure profiles show that the absolute value of the maximum urethral closure pressure is equal in the anterior/posterior and lateral aspects of the urethra. Dynamic measurement at the proximal urethra in controls shows that holding or coughing produces directional closure from posterior to anterior. The directional forces acting at the proximal urethra are observed in the region coincident with the position of the vaginal attachments to the pelvic diaphragm. Based on resting and dynamic urethral pressure measurements, evidence is presented to indicate that the microtip transducer with sensors oriented in the anterior/posterior plane provides a significant advantage in identifying urethral closure mechanisms and has contributed towards localization of anatomical structures involved in the continence mechanisms. Finally, consideration is made of urethral stability and local pressure variations detected in the absence of external periurethral influences possible interplay between the stability of the urethra on the one hand and the detrusor on the other are discussed with particular emphasis on establishing a link between them.