Pressure/cross-sectional area relations in the proximal urethra of healthy males: the time dependent pressure response following forced dilation. Part IV: results in healthy volunteers

The significance of the anatomical location and age on the urethral response to a sudden forced dilation was studied in 30 healthy males aged 23-85 years. The pressure decay after dilation was fitted with 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 pressure response was highly affected by the location of the measurement, with the maximum values of the pressure components in the high pressure zone and significantly lower values in the prostatic part of the urethra. The variation in pressure thus concurs closely with the density of the striated rhabdosphincter. No significant correlation between age and the pressure components could be demonstrated, whereas the velocity of the pressure decay following dilation proved significantly related to age in all urethral segments. The causal background for this correlation is uncertain, but may be discovered in age dependent changes in the periluminal tissue composition, or in changing neuromuscular activity in these structures.