Definition of normality of pressure-flow parameters based on observations in asymptomatic men

Clinical nomograms for differentiating obstructed from unobstructed voiding and poor detrusor contractility from normal contractility have traditionally been drawn on the basis of symptomatic response to outflow tract surgery or on urodynamic changes in men with LUTS before and after surgery. The aim of this study was to examine pressure-flow parameters in asymptomatic male volunteers before age-related changes in the lower urinary tract had taken place and to assess detrusor contractility and outflow conditions during physiological bladder filling against clinically used pressure-flow nomograms.

Thirty-seven healthy male subjects between the ages of 18 and 40 years volunteered to undergo AUM. A total of 66 fill-void cycles in 25 individuals were evaluable.

Mean p(det.Qmax) for the group was 53 +/- 3 cmH(2)O with a mean Q(max) of 24 +/- 2 ml sec(-1). URA of 21 cmH(2)O defined the upper border of normality for the outflow condition. Schäfer's OCO showed the most consistent relationship between estimated urethral pressure at minimal flow and true measured urethral closure pressure. From a clinical perspective, the linear nomograms (ICS and Schäfer) are more easily accessible with the ICS BOOI and obstruction index being the simplest to calculate manually. Minimal differences found between these urodynamic nomograms confirm the clinical value of recommending a single method to facilitate future comparisons between studies.

An upper limit of normality for the male outflow condition can be defined by an URA of 21 cmH(2)O, AGN of 40 cmH(2)O or OCO of 1. Results above these reference values should be considered abnormal in this age group and where identified in a different age-group should be explained by physiological or pathophysiological events.