Effect of 6F urethral catheterization on urinary flow rates during repeated pressure-flow studies in healthy female volunteers

Objectives. To prospectively examine the effect of a 6F urethral catheter on the urinary flow rate in healthy women without lower urinary tract symptoms undergoing pressure-flow studies. Methods. Women between the ages of 30 and 70 years, without lower urinary tract complaints and without a history of surgery for incontinence, were recruited. All women completed the Urogenital Distress Inventory-6 questionnaire, and only women with mild or no symptoms were enrolled. After a free flow rate was determined, cystometry and pressure-flow studies were performed once and then repeated using a 6F urethral catheter. The peak flow rates during the first and second studies were compared with one another and with the nonintubated values. Results. Of the 59 women that applied, 20 volunteers (mean age 41.7 years) met the entry criteria and were evaluated. The mean nonintubated flow rate was 22.65 mL/s. With a 6F urethral catheter in place, our cohort had a mean peak flow rate of 16.25 mL/s on the first study and 15.25 mL/s on the second. A significant difference was demonstrated between the free and intubated peak flow rates for both the first (P = 0.0006) and the second (P = 0.0001) study. No significant difference was detected between the two intubated peak flow rates (P = 0.262). Conclusions. Our data suggest that the presence of a 6F urethral catheter significantly reduces the maximal flow rate compared with free flow studies. Whether these findings represent a truly obstructive effect of the catheter, detrusor fatigue, or other possible effect of the catheter remains to be elucidated.