The influence of age, urethral resistance and bladder contractility on
voiding efficiency was evaluated by pressure-flow studies in 138 men of a
mean age of 60 years (range 18 to 86). From these studies the urethral
resistance parameter was calculated and the maximum bladder contraction
strength was determined. Premature fading of the bladder contraction was
quantified by a bladder contraction strength decay factor. Voiding
efficiency was expressed by the parameter of post-void residual urine
volume as a percentage of the initial bladder volume. Multiple regression
analysis showed that voiding efficiency depended significantly in
descending order of importance on urethral resistance, maximum bladder
contraction strength and bladder contraction strength decay factor.
Patient age was not an independent factor. Maximum bladder contraction
strength and bladder contraction strength decay factor were not
correlated, suggesting that maximum bladder contraction strength and its
decay constitute different properties of bladder contractile function. A
voiding efficiency nomogram is proposed, making use of the values for
maximum bladder contraction strength and urethral resistance in individual
patients. Such a nomogram may have predictive value for the occurrence of
acute retention but it must be tested prospectively