Does urethral instrumentation affect uroflowmetry measurements?

Uroflowmetry was performed before and after urethral catheterisation in 129 patients. Uroflowmetry measurements were significantly modified by urethral instrumentation. In males, both maximum and mean flow rates decreased following urethral catheterisation, while in females only the maximum flow rate decreased, the mean flow rate remaining unchanged. Voided volume increased (and consequently residual urine decreased) in females after catheterisation, but did not change significantly in males. False positive results were encountered in 32% of patients and false negative results in 11% when flowmetry was done immediately after catheterisation. Uroflowmetry after urethral instrumentation is not recommended.