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 rec
orded. Urodynamics were performed using a 7Fr double lumen transurethral ca
theter. At functional bladder capacity patients were asked to void in the s
itting position and pressure flow studies were performed. All uroflowmetry
tracings were inspected and analyzed manually. Only patients who voided sim
ilar volumes varying by less than 20% on the free and pressure flow studies
were assessed. Free and pressure flow parameters were compared according t
o voided volume category, main urodynamic diagnosis, uroflowmetry pattern a
nd 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 press
ure flow parameters were significantly different from the equivalent free f
low parameters in all but 4 cases. Specifically the maximum flow rate was s
ignificantly less and flow time was significantly longer on pressure versus
free flow studies (each p <0.01). An intermittent flow pattern was more co
mmon 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 tra
ct symptoms. This finding may have further clinical implications regarding
the interpretation of these parameters as well as establishment of an accur
ate diagnosis.