The effect of a 6 Fr catheter in women: Are they obstructive?

Our objective was to evaluate the effect of a 6 Fr transurethral catheter on the uroflowmetry and to assess whether it potentially contributes to the bladder outlet obstruction (BOO) in women.

We reviewed the charts of 1367 women who underwent an urodynamic study. We included patients with a non-invasive free-flow study (NIFFS) and pressure flow study (PFS) performed through a 6 Fr double lumen transurethral catheter.

In total, 120 women met the inclusion/exclusion criteria. Mean maximal flow rate (Qmax) was significantly higher (p < 0.001) in the NIFFS (27.2±11.1 mL/s) than in the PFS (19.3±10.6 mL/s). The mean difference between both Qmax was 7.9±12.0 mL/s. Of these women, 92.3% (24/26) with a Qmax <12 mL/s during PFS were found to have a Qmax ≥12 mL/s during the NIFFS. Ten of the 72 women with an available Pdet.Qmax were deemed to have a BOO according to the PFS and all of them had a Qmax >12 mL/s during the NIFFS. Of the 10 patients, only 2 reported obstructive symptoms.

The presence of 6 Fr transurethral catheters alters the PFS and results in a significant reduction of the Qmax in patients who voided more than 250 mL. We believe that NIFFS should be performed in all patients before any urethral manipulation to lower a possible overdiagnosis of BOO and findings should always be correlated to clinical symptoms.