Pressure/cross-sectional area relations in the proximal urethra of healthy males. Part III: the time dependent pressure response following forced dilation: standardization of a technique.

The urethral response to a sudden forced dilation was studied in ten healthy male volunteers aged from 27 to 71 years. Measurements were performed from the bladder neck and beyond the region of high pressure using a specially designed probe. The pressure response after dilation showed a characteristic course, which could be described by a double exponential function of the form: P(t) = P(equ) + P(alpha)e(-t/tau(alpha) + P(beta)e(-t/tau(beta) where P(t) is pressure at time t, P(equ) is equilibrium pressure after dilation, P(alpha) and P(beta) are pressure decay, and tau(alpha) and tau(beta) are time constants. The size and velocity of dilation, as well as the degree of distension before dilation, proved of significance for the magnitude of the pressure response. The characteristics of the pressure response are given by the properties of the periluminal structures strained during dilation, and are thus predominantly determined of elastic, collagen, muscular, and glandular components. However, a high degree of relaxation after straining, and a modest stiffness, indicates that the muscular component dominates the response. The significance of the prostatic tissues remains unclear.