Pressure/flow studies in elderly men without voiding problems: Estimation of the urethral pressure/flow relation and urethral elasticity

The flow in the urethra is controlled by an elastic constriction, the flow‐controlling zone. The distensibility of this zone is described by the pressure/area relation, which gives the static pressure as a function of the cross‐sectional area at the flow‐controlling zone. The pressure/area relation can be calculated from the pressure/flow relation, which is estimated from the pressure/flow plot obtained at a urodynamic examination. In this study the urethral pressure/flow and pressure/area relations were estimated for 21 randomly selected men (62–75 years old) without voiding problems. Nineteen of 21 persons in this group had pressure/flow relations with a low slope. This corresponds to a low slope in the pressure/area relation indicating high distensibility of the flow‐controlling zone, which for 18 persons was estimated to be distended to areas larger than 10 mm 2 during micturition. Twenty persons had a minimal urethral opening pressure below 55 cm H 2 O. The estimated pressure/area relation was linear in 59% of the micturitions, indicating that the flow‐controlling zone could have been distended to a larger cross‐sectional area, if the bladder had achieved a higher pressure. The 10th–90th percentiles for maximum flow and detrusor pressure at maximum flow were 7.2–24.3 ml/s and 24–76 cm H 2 O, respectively. Four persons had low flow and low pressure, indicating diminished detrusor contractility with age. Twenty‐four percent of the persons had unstable bladder contractions with a pressure rise < 15cm H 2 O and 19% with a pressure rise < 15cm H 2 O.