Study on the relation of the shape of the uroflowmetrogram and the urethral loss coefficient calculated from the uroflowmetrogram

Abstract

排尿のシミュレーションを使い, 尿流曲線の近似から計算された尿道の損失係数が尿流曲線の形を規定するパラメーターと相関するのかについて検討した.合計161例の正常異常尿流曲線を使用した結果, 1)最大尿流率(Qmax)とflow timeの比Qmax/Tは尿道の損失係数(LC)と強い相関を認めた. 2)Qmax/Tは尿流曲線の縦横比であるが, 排尿中の平均的な流量の加速の度合いを示していた. 3)尿流曲線の形から尿道の損失係数が推定でき, Qmax/TはQmaxに比較して排尿量の影響が少なかった. 4)Qmax/Tは排尿量に依存する程度が小さく排尿量の異なる症例を比較するのに適当である

The shape of the uroflowmetrogram reflects voiding conditions. Using a voiding simulation, we examined whether the urethral loss coefficient (LC) calculated from the approximated uroflowmetrogram correlates with parameters that regulate the shape of the uroflowmetrogram. A total of 161 normal and abnormal uroflowmetrograms were used. Normal female subjects and patients before and after transurethral resection of the prostate (TURP) were also studied. The ratio of maximum flow rate (Qmax) to flow time (T), a parameter expressing the shape of the uroflowmetrogram, was calculated. The uroflowmetrograms were approximated using a voiding model, and the urethral LC was calculated. As a result, a strong negative correlation was observed between the Qmax-flow time ratio, Qmax/ T, and LC. Qmax/T is the vertical to horizontal ratio of the uroflowmetrogram and indicates the average degree of acceleration of flow rate during voiding. On the other hand, urethral LC, which can be estimated from the shape of the uroflowmetrogram, is considered a kind of urethral resistance. We concluded that when urethral resistance is high, the degree of acceleration of flow rate is low on average. Our study also indicated that Qmax/T was less affected by voided volume (VV) compared to Qmax. As Qmax/T is not as dependent on VV, it is useful for comparing cases with different VV.