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[Usefulness of DURR (dynamic urethral resistance factor) in the study of prostatism].

OBJECTIVES
To determine the utility of the DURR (dynamic urethral resistance factor) in the evaluation of prostatism.


METHODS
248 patients with prostatism were evaluated by the detrusor pressure-flow rate test, perineal and periurethral EMG and voiding videocystography. The Audit software program was utilized to process the data from the pressure-flow studies to obtain the parameters for urethral resistance (PURR), bladder contractibility (Wmax) and DURR.


RESULTS
The presence of DURR correlated significantly with abdominal voiding pressure and voluntary voiding, and constrictive obstruction, although a higher incidence of stenosis in patients with a positive DURR was not demonstrable on videocystography. No correlation was observed between EMG activity and a positive DURR.


CONCLUSIONS
A positive DURR indicates the effect of active urethral resistance changes on the voiding dynamics. These active changes can be caused by contraction of the periurethral muscles (EMG activity), although not all of the cases showing EMG activity have a positive DURR. Furthermore, in some DURR positive cases, the EMG is silent, indicating that the urethral smooth muscles are involved in the active changes of urethral resistance. The DURR data do not always coincide with the perineal EMG findings and therefore do not supplant each other.