Normal development of bladder and sphincter control

Normal bladder storage and voiding involve low-pressure and adequate bladder volume filling followed by a continuous detrusor contraction that results in bladder emptying, associated with adequate relaxation of the sphincter complex. This process requires normal sensation and normal bladder outlet resistance. The neurophysiologic mechanisms involved in normal bladder storage and evacuation include a complex integration of sympathetic, parasympathetic, and somatic innervation, which is ultimately controlled by a complex interaction between spinal cord, brain stem, midbrain, and higher cortical structures.

Immediately after birth, voiding is very infrequent during the first few days of life. After the first week, frequency increases rapidly and peaks at the age of 2 to 4 weeks, to an average of once per hour. It then decreases and remains stable after 6 months to about 10 to 15 times per day. After the first year it decreases to 8 to 10 times per day, while voided volumes increase by three- to fourfold. Even in small infants micturition does not occur during sleep.

In response to bladder distension during sleep, an infant nearly always exhibits clear electro-encephalographic evidence of cortical arousal, facial grimaces or limb movements, or actual awakening. Sleeping infants are always seen to wake up before the bladder contracts and voiding occurs. This arousal period may be transient and the infant may cry and move for a brief period before micturition, and then shortly afterward go back to sleep. The control of micturition involves complicated neural pathways and higher centers. A pronounced reorganization of pre-existing synaptic connections and neural pathways involved in bladder and bowel control occurs during the early postnatal period.

In newborns micturition occurs at frequent intervals and may have an intermittent pattern that will disappear with increasing age. They are thought to represent variations between individual infants in the maturation of detrusor and sphincteric coordination during the first 1 to 2 years of life. Voiding pressures are much higher than in adults, especially in boys.

Between the age of 1 and 2, conscious sensation of bladder filling develops. The ability to void or inhibit voiding voluntarily at any degree of bladder filling commonly develops in the second and third years of life. Central inhibition is crucial to obtain continence.

During the second and third year of life, there is progressive development toward a socially conscious continence and a more voluntary type of micturition control develops. Through an active learning process, the child acquires the ability to voluntarily inhibit and delay voiding until a socially convenient time, then actively initiate urination, even when the bladder is not completely full, and allow urination to proceed to completion.

The final steps are usually achieved at the age of 3 to 4 years, when most children have developed the adult pattern of urinary control and are dry both day and night. The child has learned to inhibit a micturition reflex and postpone voiding and voluntarily initiate micturition at socially acceptable and convenient times and places. This development is also dependent on behavioral learning and can be influenced by toilet training, which in turn depends on cognitive perception of the maturing urinary tract.

It is understandable that this series of complex events is highly susceptible to the development of various types of dysfunction. Various functional derangements of the bladder-sphincter-perineal complex may occur during this sophisticated course of early development of normal micturition control mechanisms.

Fecal incontinence during childhood may be a symptom of delayed acquisition of toileting skills or may reflect serious underlying organic or functional pathology. There are considerable cultural differences in toilet training, and across the world children acquire bowel control at anytime between 1 year and 4 years of age.

The pattern of bowel actions changes during early life from an average of three stools per day in the neonate to 1.7 stools per day at 1 year of age. Among preschool children in the United Kingdom, 97% will pass stool within the range three times per day to alternate days.

Pathophysiology and classification of urinary incontinence

Urinary incontinence in children may be caused by a congenital anatomic or neurologic abnormality, such as ectopic ureter, bladder exstrophy, or myelomeningocele. In many children, however, there is no obvious cause for the incontinence and they are referred to as having “functional incontinence.”

On the basis of urodynamic studies, the functional dysfunctions can be termed “urge syndrome” (detrusor overactivity), “dysfunctional voiding” (detrusor-sphincter dyscoordination), “underactive bladder” and “non-neurogenic neurogenic bladder” (occult neurogenic bladder). Functional urinary incontinence in children may be because of disturbances of the filling phase, the voiding phase, or a combination of both ( Table 1 ).

Overactivity of the detrusor muscle may lead to disturbances in the filling phase, characterized by urgency, frequency, and at times urge incontinence, often associated with nocturia that is present in the absence of pathologic or metabolic factors that may cause or mimic these symptoms. Urge syndrome is best characterized by frequent episodes of an urgent need to void, countered by contraction of the pelvic floor muscles (guarding reflex) and hold maneuvers, such as squatting and the Vincent curtsey sign. The voiding phase is essentially normal, but detrusor contraction during voiding may be extremely powerful.

The etiology of the overactive bladder in children is unclear, but it appears to be related to a lack of ability to voluntarily inhibit the infant voiding reflex, a delay in central nervous system maturation. Girls present with symptoms of detrusor overactivity more often than boys. In addition to the urinary symptoms, children with functional urinary incontinence may also have recurrent urinary tract infections and constipation. Depending on fluid intake and urine production, the complaints of incontinence become worse toward the end of the day because of loss of concentration and fatigue and may also occur during the night. Children usually diminish their fluid intake to minimize wetting, and therefore incontinence may not be the main complaint or symptom. A careful history and a bladder diary will demonstrate that they often suffer from urinary frequency and urgency, their fluid intake is small, and their voided volumes are less than expected.

Frequent voluntary contractions of the pelvic floor muscles may also lead to postponement of defecation. Constipation and fecal soiling are often found in children with overactive bladder. The constipation is aggravated by the decreased fluid intake. Constipation contributes to an increased risk of UTIs and may exacerbate the detrusor overactivity.

Incomplete relaxation or tightening of the sphincteric mechanism and pelvic floor muscles during voiding results in an intermittent voiding pattern that may be associated with elevated post-void residuals. These children with dysfunctional voiding are also prone to constipation and recurrent UTIs.

Bladder function during the filling phase in these children may be essentially normal, but detrusor overactivity may be present. The cause of dysfunctional voiding is unclear. It may be that an overactive bladder eventually leads to overactivity of the pelvic floor muscles, with subsequent insufficient relaxation during voiding. Alternatively, poor relaxation of the pelvic floor muscles during voiding may be a learned condition during the toilet training years, adopted following episodes of dysuria or constipation, or occur secondary to sexual abuse. Because no true structural obstruction can be identified, the intermittent incomplete pelvic floor relaxation that occurs during abnormal voiding is termed a functional disorder.

Urgency and incontinence of urine may result from detrusor overactivity and thus be seen in conjunction with increased urinary frequency. Alternatively, infrequent or poor bladder emptying may precipitate symptoms. Micturition is often achieved with significant abdominal activity and urodynamic investigations may show an interrupted or staccato flow pattern. Children with dysfunctional voiding have a higher rate of recurrent UTIs than children with no voiding abnormality and also demonstrate increased incidence of higher grades of vesicoureteral reflux (VUR).

The child’s environment, in particular toilet conditions and privacy issues, can trigger or exacerbate voiding anomalies. Signs of dysfunctional voiding reflect initial compensatory overactivity of the detrusor along with poor emptying ability. They may include small bladder capacity, increased detrusor thickness, decreased detrusor contractility, impaired relaxation of the external urinary sphincter during voiding, weak or interrupted urinary stream, and large PVR volumes of urine. There may also be ultrasound abnormalities, secondary VUR, fecal soiling, or constipation.

In children with an underactive detrusor, voiding occurs without detrusor contractions, and PVRs and incontinence are the main characteristics. Children with this condition void infrequently and usually present with UTIs and incontinence. A correct diagnosis can only be made by urodynamic evaluation. Long-standing overactivity of the pelvic floor may in some children be responsible for “decompensation” of the detrusor, leading to a noncontractile detrusor. However, no data are available to support this theory.

A non-neurogenic neurogenic bladder has been postulated to be the end-stage of dysfunctional voiding. It has been referred to as “occult neuropathic bladder.” A neurologic etiology must be ruled out before determining that the child’s voiding problems are consistent with the non-neurogenic neurogenic bladder. Urodynamically, non-neurogenic neurogenic bladder is characterized by diminished bladder volume and compliance. Detrusor overactivity is often present and there is contraction of the pelvic floor muscles during voiding. Videourodynamic studies or a voiding cystourethrogram (VCUG) usually show all the features of a true neurogenic bladder. These children are at risk for upper tract damage and must be fully evaluated and seen regularly.

Lettgen and colleagues. introduced the term “voiding postponement.” In this condition, children will postpone imminent micturition until overwhelmed by urgency, which makes them rush to the toilet; but often they are too late and incontinence occurs. Traditionally, this syndrome was thought to be an acquired disorder caused by detrusor overactivity and voluntary overactivity of the urethral sphincter until the bladder becomes filled.

A recent study that compared children with typical urge syndrome to those with voiding postponement revealed a significantly higher frequency of clinically relevant behavioral symptoms in postponers than in children with urge syndrome, suggesting that voiding postponement is an acquired or behavioral disorder. It remains to be determined whether or not voiding postponement can develop in the setting of a perfectly normal urinary tract or whether urge syndrome is a necessary precursor.

In some children giggling can trigger partial to complete bladder emptying well into their teenage years, and intermittently into adulthood. This condition occurs in both boys and girls and is generally self-limiting. The etiology of “giggle incontinence” is not defined. Urodynamic studies fail to demonstrate any abnormalities, there is no anatomic dysfunction, the upper tracts appear normal on ultrasound, the urinalysis is normal, and there are no neurologic abnormalities.

Urinary leakage that occurs in girls a short time after voiding to completion that is not associated with any strong desire to void may be the result of vesicovaginal entrapment. Vesicovaginal reflux may occur because of labial adhesions, a funnel shaped hymen, or an inappropriate position on the toilet. Obesity may be an associated risk factor. Changes in voiding position and treatment of labial adhesions will lead to resolution of the urine leakage.

The genitourinary tract and the gastrointestinal system are interdependent, sharing the same embryologic origin, pelvic region, and sacral innervation. Although children with voiding disturbances often present with bowel dysfunction, until recently this coexistence was considered coincidental. However, it is now accepted that dysfunction of emptying of both systems, in the absence of anatomic abnormality or neurologic disease, is inter-related.

The common neural pathways or the mutual passage through the pelvic floor musculature may provide a theoretical basis for this relationship, as may the acquisition of environmental and developmental learning. The latter can be influenced by episodes of UTI, constipation, anal pain or trauma, childhood stressors, reluctance to toilet, and poor toilet facilities.

The elimination syndrome is seen more frequently in girls than boys and is associated with the presence of both VUR and UTI. Children with elimination syndrome commonly complain of urinary incontinence, nocturnal enuresis, recurrent UTIs, urgency to void, or exceptional urinary frequency, and on investigation are often noted to have poor voiding efficiency, VUR, constipation, soiling, no regular bowel routine, and infrequent toileting.

Pathophysiology and classification of urinary incontinence

Urinary incontinence in children may be caused by a congenital anatomic or neurologic abnormality, such as ectopic ureter, bladder exstrophy, or myelomeningocele. In many children, however, there is no obvious cause for the incontinence and they are referred to as having “functional incontinence.”

On the basis of urodynamic studies, the functional dysfunctions can be termed “urge syndrome” (detrusor overactivity), “dysfunctional voiding” (detrusor-sphincter dyscoordination), “underactive bladder” and “non-neurogenic neurogenic bladder” (occult neurogenic bladder). Functional urinary incontinence in children may be because of disturbances of the filling phase, the voiding phase, or a combination of both ( Table 1 ).

Overactivity of the detrusor muscle may lead to disturbances in the filling phase, characterized by urgency, frequency, and at times urge incontinence, often associated with nocturia that is present in the absence of pathologic or metabolic factors that may cause or mimic these symptoms. Urge syndrome is best characterized by frequent episodes of an urgent need to void, countered by contraction of the pelvic floor muscles (guarding reflex) and hold maneuvers, such as squatting and the Vincent curtsey sign. The voiding phase is essentially normal, but detrusor contraction during voiding may be extremely powerful.

The etiology of the overactive bladder in children is unclear, but it appears to be related to a lack of ability to voluntarily inhibit the infant voiding reflex, a delay in central nervous system maturation. Girls present with symptoms of detrusor overactivity more often than boys. In addition to the urinary symptoms, children with functional urinary incontinence may also have recurrent urinary tract infections and constipation. Depending on fluid intake and urine production, the complaints of incontinence become worse toward the end of the day because of loss of concentration and fatigue and may also occur during the night. Children usually diminish their fluid intake to minimize wetting, and therefore incontinence may not be the main complaint or symptom. A careful history and a bladder diary will demonstrate that they often suffer from urinary frequency and urgency, their fluid intake is small, and their voided volumes are less than expected.

Frequent voluntary contractions of the pelvic floor muscles may also lead to postponement of defecation. Constipation and fecal soiling are often found in children with overactive bladder. The constipation is aggravated by the decreased fluid intake. Constipation contributes to an increased risk of UTIs and may exacerbate the detrusor overactivity.

Incomplete relaxation or tightening of the sphincteric mechanism and pelvic floor muscles during voiding results in an intermittent voiding pattern that may be associated with elevated post-void residuals. These children with dysfunctional voiding are also prone to constipation and recurrent UTIs.

Bladder function during the filling phase in these children may be essentially normal, but detrusor overactivity may be present. The cause of dysfunctional voiding is unclear. It may be that an overactive bladder eventually leads to overactivity of the pelvic floor muscles, with subsequent insufficient relaxation during voiding. Alternatively, poor relaxation of the pelvic floor muscles during voiding may be a learned condition during the toilet training years, adopted following episodes of dysuria or constipation, or occur secondary to sexual abuse. Because no true structural obstruction can be identified, the intermittent incomplete pelvic floor relaxation that occurs during abnormal voiding is termed a functional disorder.

Urgency and incontinence of urine may result from detrusor overactivity and thus be seen in conjunction with increased urinary frequency. Alternatively, infrequent or poor bladder emptying may precipitate symptoms. Micturition is often achieved with significant abdominal activity and urodynamic investigations may show an interrupted or staccato flow pattern. Children with dysfunctional voiding have a higher rate of recurrent UTIs than children with no voiding abnormality and also demonstrate increased incidence of higher grades of vesicoureteral reflux (VUR).

The child’s environment, in particular toilet conditions and privacy issues, can trigger or exacerbate voiding anomalies. Signs of dysfunctional voiding reflect initial compensatory overactivity of the detrusor along with poor emptying ability. They may include small bladder capacity, increased detrusor thickness, decreased detrusor contractility, impaired relaxation of the external urinary sphincter during voiding, weak or interrupted urinary stream, and large PVR volumes of urine. There may also be ultrasound abnormalities, secondary VUR, fecal soiling, or constipation.

In children with an underactive detrusor, voiding occurs without detrusor contractions, and PVRs and incontinence are the main characteristics. Children with this condition void infrequently and usually present with UTIs and incontinence. A correct diagnosis can only be made by urodynamic evaluation. Long-standing overactivity of the pelvic floor may in some children be responsible for “decompensation” of the detrusor, leading to a noncontractile detrusor. However, no data are available to support this theory.

A non-neurogenic neurogenic bladder has been postulated to be the end-stage of dysfunctional voiding. It has been referred to as “occult neuropathic bladder.” A neurologic etiology must be ruled out before determining that the child’s voiding problems are consistent with the non-neurogenic neurogenic bladder. Urodynamically, non-neurogenic neurogenic bladder is characterized by diminished bladder volume and compliance. Detrusor overactivity is often present and there is contraction of the pelvic floor muscles during voiding. Videourodynamic studies or a voiding cystourethrogram (VCUG) usually show all the features of a true neurogenic bladder. These children are at risk for upper tract damage and must be fully evaluated and seen regularly.

Lettgen and colleagues. introduced the term “voiding postponement.” In this condition, children will postpone imminent micturition until overwhelmed by urgency, which makes them rush to the toilet; but often they are too late and incontinence occurs. Traditionally, this syndrome was thought to be an acquired disorder caused by detrusor overactivity and voluntary overactivity of the urethral sphincter until the bladder becomes filled.

A recent study that compared children with typical urge syndrome to those with voiding postponement revealed a significantly higher frequency of clinically relevant behavioral symptoms in postponers than in children with urge syndrome, suggesting that voiding postponement is an acquired or behavioral disorder. It remains to be determined whether or not voiding postponement can develop in the setting of a perfectly normal urinary tract or whether urge syndrome is a necessary precursor.

In some children giggling can trigger partial to complete bladder emptying well into their teenage years, and intermittently into adulthood. This condition occurs in both boys and girls and is generally self-limiting. The etiology of “giggle incontinence” is not defined. Urodynamic studies fail to demonstrate any abnormalities, there is no anatomic dysfunction, the upper tracts appear normal on ultrasound, the urinalysis is normal, and there are no neurologic abnormalities.

Urinary leakage that occurs in girls a short time after voiding to completion that is not associated with any strong desire to void may be the result of vesicovaginal entrapment. Vesicovaginal reflux may occur because of labial adhesions, a funnel shaped hymen, or an inappropriate position on the toilet. Obesity may be an associated risk factor. Changes in voiding position and treatment of labial adhesions will lead to resolution of the urine leakage.

The genitourinary tract and the gastrointestinal system are interdependent, sharing the same embryologic origin, pelvic region, and sacral innervation. Although children with voiding disturbances often present with bowel dysfunction, until recently this coexistence was considered coincidental. However, it is now accepted that dysfunction of emptying of both systems, in the absence of anatomic abnormality or neurologic disease, is inter-related.

The common neural pathways or the mutual passage through the pelvic floor musculature may provide a theoretical basis for this relationship, as may the acquisition of environmental and developmental learning. The latter can be influenced by episodes of UTI, constipation, anal pain or trauma, childhood stressors, reluctance to toilet, and poor toilet facilities.

The elimination syndrome is seen more frequently in girls than boys and is associated with the presence of both VUR and UTI. Children with elimination syndrome commonly complain of urinary incontinence, nocturnal enuresis, recurrent UTIs, urgency to void, or exceptional urinary frequency, and on investigation are often noted to have poor voiding efficiency, VUR, constipation, soiling, no regular bowel routine, and infrequent toileting.

Epidemiology of urinary incontinence

Several studies have reported the prevalence of daytime incontinence. Outcomes differ as the study designs were different and definitions varied. A Swedish study showed urinary incontinence during the day in 6% of the 7-year old girls and in 3.8% of the boys. In Australia, urinary incontinence in 5- to 12-year-old children was reported in 5%. In Belgium, the reported prevalence in children between 10 to 14 years old was 8%. These studies included all forms of loss of urine during the day, from once a month to several times a day.