Purpose: We investigated whether a diagnosis of bladder outflow obstruction could be established from pressure flow analysis of a void initiated by involuntary detrusor overactivity.
Materials and methods: 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.
Results: 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.
Conclusions: 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.