A comparison of flow rate curve shape and video-urodynamic findings in women with lower urinary tract symptoms: can flow rate curve shape predict female bladder outflow obstruction or detrusor underactivity?

Purpose: To establish the correlation between flow rate curve shape and video-urodynamic findings in women with lower urinary tract symptoms (LUTS).
Methods: A retrospective review of consecutive women with LUTS who performed a free flow study immediately before undergoing video-urodynamic investigations over a 28-month period. Flow rate curve shape and video-urodynamic parameters were analysed. Free flow curves were defined into five categories: bell-shaped, prolonged, fluctuating, intermittent or plateau. Women who voided less than 150 ml on the free flow study were excluded from the analysis.
Results: A total of 250 women with LUTS, with a mean age 48 years (range 18-83), were included. Bell-shaped tracings excluded obstruction in 89%. Prolonged flow rate curves diagnosed obstruction in 62% and detrusor underactivity in 8%. Fluctuating and intermittent flow rate curves were associated with urodynamic obstruction in 37 and 39%, respectively, and detrusor underactivity in 25 and 29%, respectively. A plateau flow rate curve was indicative of urodynamic obstruction in all three cases observed.
Conclusion: Flow rate curve patterns can be suggestive of urodynamic diagnoses. Women without a prolonged void and bell-shaped traces had normal voiding urodynamics in 76% of cases, and the majority could be managed without invasive investigations. Patients with fluctuating and intermittent flow rate curves demonstrate a spectrum of urodynamic diagnoses with a third of cases having obstruction and a third of cases having detrusor underactivity. Plateau flow rate curve patterns are associated with urethral obstruction.