The influence of a urethral catheter and age on recorded urinary flow rates in healthy women.

Introducing a 7 F catheter into the urethra reduced the maximum and average flow rate and increased the micturition time significantly in healthy fertile and postmenopausal women. The menstrual cycle had no influence on the parameters. Urinary flow data were highly reproducible in both the fertile and the postmenopausal women. The flow rate-volume relation can be mathematically expressed, allowing for corrections when small voided volumes or small flow rates are obtained. Furthermore, this relation showed an increased flow time and a decreased flow rate in the postmenopausal women. This might indicate that the postmenopausal women had a reduced bladder contractility or a less compliant urethra.