Acceleration of flow rate in obstructive detrusor instability.

The acceleration of flow rate (a) was calculated from spontaneous free flow uroflowmetry in 86 males with bladder outflow obstruction due to benign prostatic hypertrophy. Forty patients had stable bladders and 46 had detrusor instability. The parameter a was also determined in 30 controls. All of the obstructed patients had lower values of a than the controls but patients with detrusor instability tended to show a higher acceleration of flow rate than those with stable bladders. In individual cases, however, parameter a was unreliable in distinguishing stable from unstable patients.