Flow rate versus bladder volume. An alternative way of presenting some features of the micturition of healthy males.

By transforming uroflowmetrograms from curves of flow rate versus time into curves of flow rate versus instantaneous bladder volume, additional information about the variation of the flow rate during voiding is obtained. These curves show that, within a certain volume range, the maximum flow rate is more or less independent of the voided volume. A second volume-independent parameter is the maximum contraction velocity, which can be calculated from the flow rate and the instantaneous bladder volume. This parameter is presumably a measure of the physiological maximum contraction velocity of the detrusor muscle.