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

It was demonstrated earlier that reduced maximum flow-rate (Q_max ) 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.

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 Q_max and detrusor pressure at Q_max (p_det.Qmax ). AG and pucp are strongly correlated. Contractility is described by a graphical representation (a nomogram) which numerical fitting is an algebraic equation f(Q_max ,p_det.Qmax ). Nomograms based on IF allowed computing a calculated AG (corr-AG) on the basis of free flow.

Included files (N = 362) had filling volume during FF > 90 mL; corr-AG was compared to AG. When Q_max.FF  > 1.5*Q_max.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 Q_max.FF  < 1.5*Q_max.IF (N = 248), only 39 patients (12.1%) were found less obstructed with corr-AG and 28 (11.3%) more obstructed.

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.