Urodynamics in female stress incontinence of urine diagnostic and pathophysiological aspects

Summary

Urodynamic investigations using simultaneous urethral and bladder pressure recordings with a microtransducer catheter were performed in the supine, sitting and standing positions on 30 patients suffering from mild (n = 15), or severe (n = 15) stress incontinence of urine and 14 symptomless women.

Zero or negative urethral closure pressures with stress, indicative of stress incontinence, appeared in 60% of the women with stress incontinence in the supine position, 77% in the sitting position and 83% in the standing position when a single cough stress was employed. In the remaining patients with clinical stress incontinence zero closure pressure was demonstrated only during the continuous stress produced by repetitive coughing in the standing position.

Filling the bladder from 100–300 ml shortened the functional length of the urethra and lowered the urethral pressure profile (UPP). The change in position from supine to standing shortened the functional length of the urethra and increased the maximal urethral closure pressure. The UPP of the incontinent women was characterized by a short functional urethra, low maximal urethral closure pressure, a small urethral pressure profile area, the sharp shape and short length of the zone of high urethral pressure and the distal location of the maximal urethral pressure point as compared with that in the continent women. The pressure transmission to the proximal urethra was similar in all the patient groups whereas that to the middle part of the functional urethra was impaired in both incontinent patient groups and even that to the distal functional urethra in the severely incontinent patients. Repetitive stress produced a decrease in the maximal urethral pressure in stress UPP as compared with the UPP at rest in all the patient groups, and significantly more so in the severely incontinent patients.

Our data indicate that the mechanisms responsible for basal urethral tonus are not fully operative in women with stress incontinence. The failure of pressure transmission to the middle urethra emphasizes the importance of the external urethral sphincter for the maintenance of urinary continence during an acute increase in intra-abdominal pressure.