Can bladder outflow obstruction be diagnosed from pressure flow analysis of voiding initiated by involuntary detrusor...

We investigated whether a diagnosis of bladder outflow obstruction could be established from pressure flow analysis of a void initiated by involuntary detrusor overactivity.

A total of 79 men with lower urinary tract symptoms were identified prospectively. In each subject 2 sequential pressure flow studies were performed during the same session. Pressure flow data were recorded during a voluntary void and voiding initiated by involuntary detrusor overactivity. Pressure flow parameters were compared using the paired t test and differences in classification according to the International Continence Society nomogram were analyzed using the chi-square test.

The maximum flow rate showed no significant difference between voluntary voiding and voiding initiated by involuntary detrusor overactivity. Detrusor pressure at maximum flow showed a slight, statistically significant but not clinically significant increase during voiding initiated by involuntary detrusor overactivity. However, the diagnostic classification remained unchanged in 64 of 79 men (80%). In no case was the diagnosis altered from bladder outflow obstruction to nonobstruction or vice versa when comparing the 2 pressure flow studies. There were significant increases in maximum detrusor pressure and detrusor pressure at the initiation of voiding during voiding initiated by involuntary detrusor overactivity.

This study demonstrates that increased detrusor pressure observed during voiding subsequent to detrusor overactivity does not change the diagnostic classification in 80% of men. The results provide evidence that bladder outflow obstruction can be reliably diagnosed based on pressure flow parameters recorded during voiding initiated by involuntary detrusor overactivity.