ウロダイナミクス研究用下部尿路シミュレーションモデル作製の研究 - 流体力学からみた理論的検討 -

Abstract

従来から報告のある管摩擦損失以外に助走区間による損失と急拡大による損失を数値として具体的に導入して流体力学モデルを作った.尿流を水の流れと仮定し, 水の密度0.99822 g/cm3, Reynolds数の因子である水の動粘性係数1.004 cm2/秒, 助走損失係数1.4, 急拡大損失係数1.0ならびにおおまかな臨床データ, 排尿時最大膀胱内圧50 cm H2O, 後部尿道の長さ5 cm, 前部尿道の長さ15 cmと径1.0 cmをモデル式に代入すると, 肥大症後部尿道径が正常後部尿道に比べてどの程度縮小すれば, 肥大症の最大尿流量率が正常のそれにくらべてどの程度減少するかが求められる

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.