[Urodynamic studies in the diagnosis of infravesical obstruction in men]

The authors have performed urodynamic investigations pressure-flow in 39 males (mean age 57.9 +/- 1.8 years) to detect infravesical obstruction. Interpretation of the findings rested upon Abrams-Griffits index (AGI) derived by the formula AGI = PdetQmax - 2xQmax, where Qmax is the maximal speed of urine flow and PdetQmax is detrusor pressure when the maximal urine flow is reached. Definite conclusion on the presence or absence of infravesical obstruction was feasible for 21(53.8%) of 39 examinees, was not possible for 18(46.2%) patients. Statistical processing yielded non-linear relationship between PdetQmax and Qmax (cubic parabola) requiring correction for AGI (coefficient K calculated according to the formula K = 58.7 - 0.00554x(Qmax)3). This correction for nonlinearity K allowed classification of 11 out of 18 patients who were initially indefinite. By standard AGI technique, the uncertainty zone made up 46.2% while correction for nonlinearity reduced this zone to 18.0% (p < 0.008). Thus, the account for nonlinearity of the relationship between PdetQmax and Qmax may contribute to a rise in diagnostic value of urodynamic investigations.