The Effect of a 6Fr Transurethral Catheter on the Urinary Flow in Female Pressure-Flow Studies

ABSTRACT

PURPOSE: We evaluated whether a 6Fr transurethral catheter affects urinary flow in women undergoing pressure-flow studies. MATERIALS AND METHODS: We retrospectively reviewed urodynamics database of 201 consecutive women referred for the evaluation of lower urinary tract symptoms from January 1997 to June 2000. Before the urodynamic study, all patients voided privately using a standard toilet and free uroflowmetry parameters were recorded. Then, a standard pressure-flow study was performed using 6Fr transurethral catheter. We excluded the patients with inadequate voided volume(<150ml) and volume difference more than 30% between two studies. Urinary flow parameters between the two studies were analysed by paired t-test according to voided volume, main urodynamic diagnosis and uroflowmetry pattern. RESULTS: Of 201 women, 144 were excluded and 57 were subjects of our analysis. According to voided volume, pressure-flow study parameters were significantly different from the equivalent free uroflowmetry parameters the maximum flow rate and average flow rate were significantly lower and flow time was significantly longer in pressure-flow studies(p<0.01). According to main urodynamic diagnosis categories, the subgroups of patients with normal urodynamic study, bladder outlet obstruction, detrusor instability and others showed significantly lower maximum flow rate and average flow rate in pressure-flow studies(p<0.01). According to uroflowmetry pattern, obstructive patterns such as undulating and intermittent pattern were more common in pressure-flow studies. CONCLUSIONS: The 6Fr transurethral catheter used in pressure-flow studies significantly affects urinary flow parameters. In order to make a accurate diagnosis, we must not merely rely on the results of pressure-flow studies, but we must take into account patient's individual clinical situation and also, if available, the results of free uroflowmetry in addition to pressure flow study parameters.