Although the term is frequently used to describe urinary incontinence regardless of its cause, more accurately, enuresis is the persistence of medically unexplained urinary incontinence after the typical age of bladder control. Subtyping occurs according to the time of day it occurs. Nocturnal enuresis is more common, and children with diurnal enuresis usually have nocturnal symptoms as well. Approximately 80% of children have primary enuresis, where bladder control has never been attained. The remaining children have previously achieved bladder control, and the term secondary enuresis is often used. The relationship between primary and secondary distinction and the incidence and severity of associated psychopathology are not clear (Table 21–31).