The effect of urethral pressure variation on detrusor activity in women

The purposes of this study were to confirm previously described patterns of urethral pressure variation and to establish criteria for their diagnosis. The effect of urethral pressure variation on detrusor activity was also examined. The study involved a retrospective review of the computerized cystometric tracings from a 26-month period. Forty-one patients had artefact-free satisfactory tracings demonstrating urethral pressure variation, detrusor instability and/or gradual detrusor pressure increase. These tracings were stored on a computer program which permitted real-time second-by-second review. Statistical analysis was done using Fisher's exact test and an independentt-test. Three patterns of urethral pressure variation were identified: rapid pressure variation (RPV), gradual pressure variation (GPV) and stress-induced transient urethral relaxation (SITUR). RPV was associated with onset at low bladder volumes (independentt-test,P=0.02) and with detrusor instability (Fisher's exact test,P<0.001). GPV began at high bladder volumes (Fisher's exact test,P<0.001). SITUR was not associated with any specific pattern of urethral pressure variation or detrusor pressure change. Analysis of tracings of the patients with a combination of rapid urethral pressure variation and detrusor instability revealed a statistically significant increased frequency of urethral relaxation as the primary event precipitating an unstable detrusor contraction (Fisher's exact test,P<0.003). In conclusion, three different patterns of urethral pressure variation were identified. Rapid pattern urethral pressure variation is closely associated with detrusor instability. Further study of urethral pressure variation may help to elucidate the pathophysiologic mechanism responsible for idiopathic unstable detrusor contractions.Editorial Comment: This investigation includes very interesting and clinically important findings. The authors describe three patterns of urethral pressure variation and their relation to the detrusor activity. Taking these activities of the urethra into consideration, especially the relationship between detrusor instability and rapid urethral pressure variation, we may select the reasonable and effective therapeutic modality for female urinary incontinence. This study is timely, adding pertinent information for clinical decision-making.