Clinicians rely on uroflowmetry configuration and voiding parameters to evaluate the need for further investigations of the lower urinary tract. Literature on the predictive value of free flow is sparse. We aim to establish the correlation between free flow configuration and video-urodynamic findings in women with lower urinary tract symptoms

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. Free flow configuration and video-urodynamic parameters were analysed. Free flow was defined in 5 categories (bell shaped, prolonged, irregular (variable but continuous flow), interrupted or plateau. Women who voided less than 150ml on free flow were excluded from the analysis

A total of 250 women with LUTS with a mean age 48 years (range 18 – 83) were included. Urodynamic diagnoses are detailed in Table 1.
Bell shaped tracings excluded obstruction in 89%. Prolonged free flows diagnosed obstruction in 62% and hypocontractility in 8%. Irregular and interrupted free flows were associated with urodynamic obstruction in 37% and 39% respectively and hypocontractility in 25% and 29%. A plateau flow was indicative of urodynamic obstruction in all 3 cases

Women without a prolonged void and bell shaped trace had normal voiding urodynamics in 76%, and could be managed without invasive investigation in the majority. Patients with irregular and interrupted flows demonstrate a spectrum of urodynamic diagnosis with a third having obstruction and a third hyponcontactility. Plateau flows are universally associated with urethral obstruction

A free flow is suggestive of urodynamic diagnosis.