Detrusor instability score in the evaluation of stress urinary incontinence

The major cause of failure in the surgical treatment of stress urinary incontinence (SUI) in women is an occult detrusor instability. In order to detect detrusor instability and its degree, urological histories were standardized by scoring the replies to ten specific questions with O (indicative of SUI), 1 or 2 (slightly and markedly indicative of detrusor instability, respectively). The sum of the scores was termed the "detrusor instability score" (DIS). The DIS was calculated for 134 patients both preoperatively and 2 years after operation, and 112 of these women were also evaluated by bead-chain urethrocystography (UCG) before operation. The 10% failure rate among the 72 patients with a DIS of 0-7 (exclusive or nearly exclusive detrusor instability) was significantly less than the 32% rate in the 62 women with a DIS of 8-16 (SUI complicated by marked detrusor instability). The 38% failure rate in 47 women of peri- or post-menopausal age and having a DIS of 8-16 was higher than the 10% in the other 87 women. An increased risk of failure was also found in patients who had a DIS of 8-16 together with either a urethral inclination angle of 80 degrees or less (46% failure rate in 28 women) or a posterior urethrovesical angle of 160 degree or less (43% failure rate in 30 women) in lateral bead-chain UCG during straining. The mean DIS decreased after successful surgery, but remained constant in cases of failure. The scored urological data facilitate the detection of patients with detrusor instability. This is potentiated by those lateral bead-chain UCG findings which indicate a low motility of the proximal urethra or bladder neck.