Tests for 'detrusor instability' in women. These mainly measure the urethral resistance created by pelvic floor contraction acting against a premature activation of the micturition reflex.

The principal aim of this study was to analyse the simultaneous pressure readings derived from bladder and urethra during a handwashing test. A total of 163 patients with urinary incontinence were studied. It was demonstrated that contraction of the pelvic floor stretches the vagina. In many patients, this appeared to inhibit the micturition reflex, possibly by supporting the nerve endings at bladder neck, thereby inhibiting their premature activation. There was also evidence that this stretching activated reflex contraction of the urethra, the vagina-urethral (coital) reflex, thereby increasing the urethral resistance. On further analysis, it was concluded that urodynamic testing does not detect 'detrusor instability' per se. It detects the urethra's attempts at closure.