Home-monitoring of uroflow in normal male adolescents. Relation between flow-curve, voided volume and time of day.

Thirteen males, age 25-40 years, without history of voiding dysfunction were investigated with repeated uroflowmetry at their own lavatories to rule out psychological influence of unfamiliar surroundings. The relationship between maximum flow rate (Qmax) and voided volume (VV) was highly reproducible. The best fitting curve was in all instances parabolic, Qmax = a.VVb, but there was a large interindividual variation in the relationship with the index, b, ranging from 0.06 to 0.52. Most of the micturitions showed VV between 125 and 525 ml, and in this interval a linear regression gave the same result concerning the degree of correlation as a parabolic, thus simplifying the calculations. There was no correlation between the maximum rate of increase in flow rate and VV, while time to maximum flow rate and VV were significantly correlated, but none of these parameters offered any advantages compared to Qmax. VV was significantly greater in the morning, while Qmax was greatest in the evening, and a possible explanation is discussed. No difference was found in the normal range for the Qmax/VV relationship compared to traditional investigations carried out in hospital or outpatient clinic. However, bearing in mind the possible influence of psychological factors on micturition in certain groups of patients it is concluded that home-monitoring of uroflowmetry is easily carried out and provides valuable clinical information in selected groups.