Detrusor instability and bladder outflow obstruction. Evidence for a correlation between the severity of obstruction and the presence of instability.

Forty patients with bladder outflow obstruction due to benign prostatic hypertrophy were assessed by means of symptom analysis, rectal examination, intravenous urography and/or cystoscopy, medium-fill water cystometry and pressure flow study. No significant correlation was found between the severity of obstruction and the degree of instability, but the occurrence of instability did correlate with the degree of obstruction. This latter conclusion, though logical, had not been proved before, and was achieved by means of a new urodynamic parameter.