Detrusor pressure uroflowmetry studies in women: effect of a 7FR transurethral catheter

Purpose: We evaluated whether a 7Fr transurethral catheter affects urinary flow in women undergoing pressure flow studies for voiding symptoms. Materials and Methods: We reviewed a urodynamic database of 600 consecutive women referred for the evaluation of voiding symptoms. Before urodynamics all patients voided privately using a standard toilet and free flow was recorded. Urodynamics were performed using a 7Fr double lumen transurethral catheter. At functional bladder capacity patients were asked to void in the sitting position and pressure flow studies were performed. All uroflowmetry tracings were inspected and analyzed manually. Only patients who voided similar volumes varying by less than 20% on the free and pressure flow studies were assessed. Free and pressure flow parameters were compared according to voided volume category, main urodynamic diagnosis, uroflowmetry pattern and pre-void bladder volume. Results: A similar volume was voided on the free and pressure flow studies of 100 women. In each voided volume category and urodynamic diagnosis pressure flow parameters were significantly different from the equivalent free flow parameters in all but 4 cases. Specifically the maximum flow rate was significantly less and flow time was significantly longer on pressure versus free flow studies (each p <0.01). An intermittent flow pattern was more common on pressure than in free flow measurements (43% versus 9%). Conclusions: A 7Fr transurethral catheter may adversely affect uroflowmetry parameters in women undergoing pressure flow studies for lower urinary tract symptoms. This finding may have further clinical implications regarding the interpretation of these parameters as well as establishment of an accurate diagnosis.