The day and night output of urine in enuresis.

The excretion of urine is one of several bodily activities which is subject to a daily rhythm. It has been clearly demonstrated how the rate of urine output is reduced during the hours normally devoted to sleep and how this rhythmic reduction in flow persists in spite of regular fluid intake throughout the 24 hours and in spite of alteration in the periods of sleep and activity (Mills, 1951). The average adult secretes just over half the amount of urine by night that he does by day, though individual variation is wide, and this applies to children from infancy upwards (Beyer and Kayser, 1949). The belief that there is a group of nocturnal enuretic children who wet the bed because they lack this ability to inhibit the urine flow at night is now quite widely held. Friedell (1927) studied 39 enuretics and found that eight of them passed urine of relatively low specific gravity at night; it was this group which he found particularly resistant to treatment. Smellie (1949), in discussing the pathogenesis of the condition, stated that nocturnal polyuria had not been sufficiently emphasized, and that it was an outstanding feature of most cases. Holman (1954) seems to have been of the same opinion, for her book on bedwetting contains the following reference to the matter: