The pathophysiology of enuresis in children and young adults.

Bedwetting is the most common urologic complaint among children. Wetting frequency at age 7 years varies from 5% to 15%. Treatment has been multimodal: drugs to depress bladder activity, increase urethral resistance, or modulate sleep; electrophysiologic treatment; and, recently, urine production modulation. All of these approaches reflect a lack of sufficient knowledge of the underlying pathophysiology of nocturnal enuresis. Over the last 13 years, enuresis studies at the Institute of Experimental Clinical Research, the University of Aarhus, Denmark, have focused on sleep disturbances, bladder reservoir function, urine output, and a combination of the three. Sleep studies indicate that: enuretic patients are normal sleepers; the voiding characteristics of an enuretic episode are similar to those of voluntary voiding during the day; and enuresis can take place during any stage of sleep, but generally occurs when the bladder is filled to the equivalent of maximal daytime functional capacity. Bladder reservoir capacity appears to be normal and bladder instability an unimportant factor in the pathology of nocturnal enuresis. However, enuretic patients have been shown to lack the normal nocturnal increase in antidiuretic hormone levels and had nocturnal urine production up to four times the volume of functional bladder capacity, which explains the need for bladder emptying. These findings open new avenues to the approach to treatment based on antidiuretic therapy.