The unstable female urethra.

Four hundred forty-seven patients with urinary incontinence were examined at the outpatient clinic and then referred to urodynamic investigation by urethral pressure profile measurement and simultaneous urethrocystometry. On urodynamic investigation, 55 patients showed signs of an unstable urethra (momentary variations in urethral pressure exceeding an amplitude of 15 cm of water by or without registration of bladder instability). Urethral instability was found in 15 patients with stress incontinence, in 23 patients with urge incontinence, and in 13 patients with combined stress and urge incontinence (i.e., signs and symptoms of both stress and urge incontinence). In four patients, urethral instability was the only pathologic finding when the recordings were made. From the pressure recordings, three types of urethral instability could be recognized: type 1, relatively small fluctuations in the urethral pressure at large bladder volumes; type 2, relatively large variations in urethral pressure with frequent decreases in the pressure, often combined with signs of unstable bladder; type 3, marked variations in the urethral pressure which appeared already at the start of urethrocystometry, i.e., at low bladder volumes. The variations in urethral pressure prevailed during the whole recording procedure, whereas bladder pressure was completely stable at all times.