[A study of the simulation model of the lower urinary tract for urodynamics--(the first report)--theoretical evaluation of hydrodynamic model].

From the view point of urodynamics, the lower urinary tract might be able to be simulated by a hydrodynamic model, consisting of a spherical balloon corresponding to the bladder and a circular tube to the urethra. In this hydrodynamic model, the diameter of the tube corresponding to the posterior urethra was assumed to become smaller with increase of the prostatic pressure according to the development of BPH. On this assumption, Bernoulli's equation might be adopted. Because of the turbulent flow in the tube, the velocity of flow was expressed as a function of the invariants, which indicated the pressure in the balloon, the respective lengths and diameters of narrow tube and wide tube, coefficients due to pipe friction, pipe fitting and pipe enlargement. The findings suggested that the smaller the diameter of the narrow tube, the smaller the flow volume showed with the development of BPH. In conclusion the urodynamics in the lower urinary tract could be simulated quantitatively by this model. The study may lead to the development of the urodynamic simulation model for the lower urinary tract.