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  • Title: A novel quantitative method for measuring obstruction in the upper urinary tract: the 'obstruction coefficient'.
    Author: Lovasz S, Lovasz L, Nyirady P, Romics I.
    Journal: Int J Urol; 2008 Jun; 15(6):499-504. PubMed ID: 18422573.
    Abstract:
    OBJECTIVES: To define an exact pressure-flow correlation in the upper urinary tract using an improved measurement method, to quantitatively characterize the degree of postrenal obstruction and to find a simple way of calculating it in everyday urological practice. METHODS: The data of 112 cases were included in the analysis. The dynamic method of a multistep, constant pressure perfusion study was used to precisely measure a wide range of pressure-flow dependences. Values of established parameters measuring the degree of obstruction were compared: the intrapelvic pressure, the ureteral opening pressure and the newly introduced 'obstruction coefficient'. RESULTS: Pressure-flow relations can be best presented by a parabolic curve described by the simple formula Y = AX(2) + B. Depending on the degree of obstruction, the shape of this curve can be characterized by a single number, that we defined as the 'obstruction coefficient'. Computer-based evaluation software for the easy calculation of this coefficient is presented here and freely available on demand. The Whitaker-test, the ureteral opening pressure, and the 'obstruction coefficient' showed significant correlation proving that the latter was clinically applicable in measuring the degree of obstruction. CONCLUSION: Calculation of the 'obstruction coefficient' enables us to exactly define the degree of upper urinary tract obstruction and to safely monitor for a long period conditions inhibiting ureteric passage.
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