To investigate the impact of urethral catheterization on uroflow by comparing urodynamic parameters of free uroflowmetry versus pressure-flow study in adult patients with benign prostatic hyperplasia, female stress incontinence, lumbosacral spinal injury or spina bifida.

Each patient was required to perform pressure-flow study immediately following free uroflowmetry. Maximum flow rate (Q_max), average flow rate (Q_ave), voided volume (VV), T_max (time to Q_max) and post-voiding residual urine (PVR) were compared between the two tests.

Out of 120 patients, transurethral catheterization significantly impacted uroflow. In male patients with benign prostatic hyperplasia (n = 50), Q_max, Q_ave and T_max were significantly different between free uroflow and pressure-flow study. In patients with female stress incontinence (n = 30), there were no statistically significant between-test differences in VV and T_max, but Q_max, Q_ave and PVR were significantly different. In patients with spinal injury or spina bifida (n = 40), Q_max, Q_ave and VV were significantly different between free uroflow and pressure-flow study.

Urethral catheterization adversely impacts uroflow in patients with benign prostatic hyperplasia, female stress incontinence, spinal injury or spina bifida. Free uroflowmetry should be performed before pressure-flow study.