Detrusor contraction duration as a urodynamic parameter of bladder outlet obstruction for evaluating men with lower urinary tract symptoms.

PURPOSE: Recent studies suggest that detrusor contraction duration increases with bladder outlet obstruction and correlates with the American Urological Association (AUA) symptom index. Since the detrusor contraction duration may also depend on detrusor contractility and bladder volume, its use alone in characterizing bladder outlet obstruction is debatable. Therefore, we studied the relationship between detrusor contraction duration and bladder outlet obstruction, bladder capacity, detrusor contractility and symptoms to determine whether detrusor contraction duration is a useful parameter for characterizing bladder outlet obstruction in men with lower urinary tract symptoms.

MATERIALS AND METHODS: Pressure-flow studies were performed in men with lower urinary tract symptoms. Bladder outlet obstruction was defined as passive urethral resistance relation greater than grade II and contractility was determined from Schäfer's nomogram. Detrusor contraction duration was defined as the contraction time elapsed between the first rise in detrusor pressure from baseline to the time at which detrusor pressure returned to baseline at the end of voiding. AUA symptom index was attained from each patient and categorized as mild (0 to 7), moderate (8 to 19) and severe (20 to 35).

RESULTS: Detrusor contraction duration was determined from 58 consecutive pressure-flow studies. This parameter was not significantly different among 23 patients with mild (116.7+/-34.0 seconds), 15 with moderate (102.7+/-61.9 seconds) and 9 with severe (89.2+/-44.4 seconds) AUA symptom index scores. AUA symptom index, as well as irritative and obstructive scores did not significantly correlate with detrusor contraction duration. Detrusor pressure at maximal flow was weakly correlated with detrusor contraction duration (r=0.322, p=0.014). However, detrusor contraction duration in 27 obstructed patients (111.6+/-53.7 seconds) was not significantly different from that of 31 nonobstructed patients (91.5+/-41.5 seconds) and it did not increase with the severity of bladder outlet obstruction. Detrusor contraction duration in 40 patients with good contractility (94.3+/-49.2 seconds) was significantly lower than in 18 patients with poor contractility (115.5+/-43.3 seconds). Detrusor contraction duration was significantly lower in nonobstructed patients with good contractility (72.0+/-21.7 seconds) compared with either nonobstructed patients with poor contractility (118.4+/-47.7 seconds) or obstructed patients with good contractility (112.5+/-58.0 seconds). There was no difference in detrusor contraction duration between nonobstructed patients with poor contractility and obstructed patients with good contractility. Multiple regression analysis showed that detrusor contraction duration can be best predicted by a combination of detrusor pressure at maximal flow, bladder capacity and contractility (r=0.576).

CONCLUSIONS: Our study showed that detrusor contraction duration cannot distinguish patients with from those without bladder outlet obstruction, and it does not correlate with the severity of symptoms. Since our results also showed that detrusor contraction duration depends on several factors related to detrusor and outlet function, it cannot be used as a reliable parameter to diagnose bladder outlet obstruction.