Are nomograms based on free uroflows helpful to evaluate urethral obstruction in men?

Abstract

Aims: It was demonstrated earlier that reduced maximum flow-rate (Qmax) during intubated flow (IF) in women may be the consequence of a urethral reflex. Over-estimation of outflow obstruction is the consequence. Our hypothesis, that a similar phenomenon could occur in men, is tested using results of a free uroflow (FF) preceding an IF to eventually correct the Abrams-Griffiths (AG) number. Methods: Retrospectively, analysis of 441 urodynamic studies of men suspected of bladder outflow obstruction (BOO) was performed. The Valentini-Besson-Nelson model links outflow obstruction (parameter pucp) and the detrusor contractility (parameter k) to Qmax and detrusor pressure at Qmax (pdet.Qmax). AG and pucp are strongly correlated. Contractility is described by a graphical representation (a nomogram) which numerical fitting is an algebraic equation f(Qmax,pdet.Qmax). Nomograms based on IF allowed computing a calculated AG (corr-AG) on the basis of free flow. Results: Included files (N = 362) had filling volume during FF > 90 mL; corr-AG was compared to AG. When Qmax.FF > 1.5*Qmax.IF (N = 114), 61 patients (53.5%) were found less obstructed with corr-AG, no one more obstructed. Increased BOO could be the result of a urethral reflex during IF and AG gave an overestimation. When Qmax.FF < 1.5*Qmax.IF (N = 248), only 39 patients (12.1%) were found less obstructed with corr-AG and 28 (11.3%) more obstructed. Conclusion: To obtain a reliable evaluation of BOO in men, it is suitable to perform a FF before IF. A corrected AG (corr-AG) obtained from IF analysis and nomograms based on FF may be helpful for evaluation of BOO in men.