Idiopathic overactive bladder (OAB) is a term that has been adopted by the International Continence Society (ICS) to describe the symptom complex of urinary urgency, which may or may not be associated with urgency urinary incontinence, urinary frequency, and nocturia in the absence of pathologic or metabolic factors that cause or mimic these symptoms. 
In the pediatric literature, OAB is often referred to as urge syndrome and is best characterized by frequent episodes of an urgent need to void, countered by contraction of the pelvic floor muscles and holding maneuvers such as squatting and the Vincent curtsy sign.
The cardinal symptom of OAB is urgency, which is defined as a sudden compelling desire to void that is often difficult to defer. Urgency must be differentiated from the urge to void, which is a normal sensation experienced by all individuals and may be intense when urine is held for a prolonged period.
The definition of urinary frequency in a child is not well established. However, many believe that a child who has a normal fluid intake and who voids more than 7 times per day has urinary frequency. The ICS defines nocturia as the need to wake at night 1 or more times to void.
Depending on fluid intake and urine production, children may experience more episodes of incontinence later in the day as a consequence of fatigue and an impaired ability to concentrate. In some cases, children with OAB remain dry during the day yet wet at night. However, such children experience daytime urgency and, often, daytime frequency.
For more information, see Overactive Bladder.
The symptoms of OAB are believed to be caused by detrusor overactivity during the filling phase, which causes urgency (see the image below).  These detrusor contractions are countered by voluntary contraction of the pelvic floor muscles in an attempt to postpone voiding and to minimize wetting. The voiding phase is essentially normal but may be associated with a powerful detrusor contraction during voiding. Childhood incontinence in girls has been noted to be a risk factor for urge symptoms and severe incontinence in adult women. 
The natural history of OAB is not well understood. Many believe that idiopathic OAB in children is the result of a maturation delay and that it resolves over time. This belief is in contrast to the theory behind OAB in adults, in whom the condition is believed to be chronic.
In children, OAB may arise from various etiologies, including neurogenic, anatomic, inflammatory, and idiopathic causes. Neurogenic etiologies include myelomeningocele, cerebral palsy, spinal cord injury, sacral agenesis, and imperforate anus. Twenty-two percent of children with a lumbosacral myelomeningocele have uninhibited bladder contractions.  In children with cerebral palsy, an unstable bladder is the most common urologic anomaly.
The most common anatomic abnormality associated with OAB is posterior urethral valves; 24% of males with this condition have OAB.  Inflammatory processes in the bladder wall (eg, urinary tract infections [UTIs]) may irritate receptors in the submucosa and detrusor muscle layers and may lead to OAB symptoms. Idiopathic OAB is thought to be secondary to delayed maturation of the reticulospinal pathways and inhibitory centers in the midbrain and cerebral cortex.
In a prospective multicenter study performed in 16 Korean medical school hospitals in 2006, the risk factors for OAB were evaluated. Enuresis, constipation, fecal incontinence, urinary tract infection, and delayed toilet training were considered risk factors associated with OAB. 
United States statistics
The prevalence of OAB in children is difficult to determine. To date, studies have focused primarily on daytime versus nighttime incontinence and have not attempted to differentiate the type of daytime incontinence. In a population survey of 1,192 individuals aged 1.5 to 27 years, diurnal accidents occurred in 13% of children aged 4 years, 7% of children aged 5 years, 10% of children aged 6 years, and 5% of children aged 7 years. 
Studies performed outside the United States have demonstrated that 2-4% of 7-year-old children have daytime or combined daytime and nighttime incontinence at least once per week and that it is more common in girls than in boys. 
In a population-based study of children aged 4-6 years in Australia, 19.2% had at least 1 daytime wetting episode in the preceding 6 months, with 16.5% having experienced more than 1 wetting episode and only 0.7% experiencing wetting on a daily basis.  Up to 50.7% of children with daytime wetting have been noted to have urgency, with 79% wetting themselves at least once in a 10-day period. 
Age-related differences in incidence
Sexual differences in incidence
Hellstrom et al, assessing the prevalence of urinary incontinence in 7-year-old Swedish children, found that diurnal incontinence was more common in girls (6.7%) than in boys (3.8%).  Wetting every week was reported in 3.1% of girls and in 2.1% of boys. Most children with diurnal incontinence had other symptoms. Urgency was reported in 4.7% of girls and in 1.3% of boys.
The natural history of OAB in children is unknown. Similarly, data on the optimal duration of therapy limited are limited. OAB in children is not believed to be a chronic condition; however, little long-term information is available.
Curran et al, in a study of the long-term results of conservative treatment in children with idiopathic detrusor overactivity, reported that the average time to resolution of symptoms was 2.7 years. The authors noted that children with very small or large bladders were less likely to benefit from conservative management. Age and gender were not significant predictors of resolution, although symptom resolution was more likely in girls than in boys. 
Patient education is an important aid to management. Both the patients and their parents or caregivers must be educated on normal bladder and sphincter function.
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