eMedicine Specialties > Pediatrics: Surgery > Urology

Voiding Dysfunction

Author: Christopher S Cooper, MD, FACS, FAAP, Associate Professor of Urology, Director of Pediatric Urology, University of Iowa, Children's Hospital of Iowa; Associate Dean for Student Affairs and Curriculum, University of Iowa Carver College of Medicine
Coauthor(s): Kenneth G Nepple, MD, Resident Physician, Department of Urology, University of Iowa Hospitals and Clinics; Stanley Hellerstein, MD, Pediatric Nephrologist, Children's Mercy Hospital of Kansas City; Ernest L Glasscock, MD Chair in Pediatric Research, Professor of Pediatrics, University of Missouri School of Medicine at Kansas City
Contributor Information and Disclosures

Updated: Jun 24, 2008

Introduction

Background

Voiding dysfunction is a common problem in children and accounts for as many as 40% of pediatric urology clinic visits. The challenge for the clinician is to differentiate a pathologic pattern of urgency or incontinence due to an underlying urologic abnormality from benign conditions related to incomplete or abnormal toilet training. Normal voiding frequency in children (after attainment of bladder control or age 5 y) is defined as 4-7 voids per day. Voiding symptoms (eg, urgency, frequency, incontinence) reflect alterations in urinary bladder function. The pathogenesis of voiding disorders is best understood and managed when considered as deviations from the normal voiding cycle consisting of bladder filling with urine storage followed by bladder emptying with voiding.

Infants regularly void by detrusor (bladder muscle) contraction as much as hourly, with small voided volumes and incomplete bladder emptying. With increasing age, bladder function matures and bladder capacity increases. Children aged 2-5 years have increased awareness of bladder fullness and develop the ability to volitionally void or inhibit voiding until it is socially acceptable. During this period, acquisition of cortical control of micturition occurs. Many forms of voiding dysfunction can be thought of as a delay in the acquisition of daytime urinary control, which typically occurs by age 4 years.

Daytime wetting is considered a problem in developmentally normal children aged 4 years or older who are wet several days each week and in previously continent children who develop daytime wetting.

Persistent daytime urinary incontinence may have an underlying neurologic, anatomic, infectious, or functional basis. This article focuses on daytime voiding disorders in children without neurologic, anatomic, obstructive, or infectious abnormalities of the urinary tract; however, any child with evidence of neurological dysfunction (eg, cutaneous signs, physical examination findings, severely refractory voiding dysfunction, urodynamic evidence of neurogenic bladder) should be further evaluated for occult neurologic lesions. Isolated nocturnal enuresis, which may be considered a form of voiding disorder, is considered elsewhere and is not reviewed here.

Pathophysiology

The micturition cycle involves 2 discrete processes: (1) bladder filling and storage of urine and (2) bladder emptying with voiding. These functions are cyclic in nature.

During the filling phase of micturition, regulatory influence of the sympathetic nervous system allows the bladder to expand at low pressure. Urine storage is a coordinated response of the sympathetic-mediated inhibition of detrusor contractile activity. The primary neurotransmitter for sympathetic activity is norepinephrine.

Expulsion of urine normally occurs as a result of simultaneous voiding contraction of the detrusor muscle and relaxation of the bladder outlet (urethra, bladder neck, and pelvic floor muscles). This is mediated by the parasympathetic nervous system, in which the primary neurotransmitter is acetylcholine. During bladder filling, afferent impulses are transmitted to sensory neurons in the dorsal root ganglia of sacral spinal segments 2-4 and convey information to the brainstem. Nerve impulses from the brainstem during bladder filling inhibit parasympathetic outflow from the sacral spinal micturition center. During the voiding phase, inhibition of the sacral parasympathetic outflow is removed, and detrusor contraction occurs. Somatic impulses traveling along the pudendal nerve act to relax the muscle of the external sphincter. The result is expulsion of urine with minimal outlet resistance.

CNS control over the lower urinary tract coordinates the micturition cycle. Normal development is characterized by increasing awareness of bladder distension and acquisition of the ability to inhibit voiding. Voiding symptoms in the neurologically and anatomically intact child, who has neither a urinary tract infection (UTI) nor local urethral irritation, is a result of functional disturbance of the normal micturition cycle.

Frequency

United States

A study of children aged 5-9 years (n = 583) showed that urinary urgency and pelvic-tightening maneuvers to postpone voiding and prevent leakage were the most common voiding problems.¹ Urge incontinence was reported in 7% of girls and in 3% of boys.

Daytime wetting has been reported to decrease with age. The prevalence of daytime wetting with a frequency of at least once every 2 weeks was 10% in children aged 5-6 years, 5% in children aged 6-12 years, and 4% in children aged 12-18 years.

International

Large studies from Sweden have addressed the frequency of voiding disorders in school-aged children. A Swedish study of 7-year-old students (n = 3556) showed that 21% of girls and 18% of boys had moderate to severe urinary urgency.² Daytime urinary incontinence occurred at least once weekly in 3.1% of girls and 2.1% of boys.

Mortality/Morbidity

A child with a voiding disorder may have few symptoms or frequent urinary tract problems. Children with functional voiding disorders may have ongoing urge incontinence, urinary dribbling, or recurrent UTIs. These children may experience severe social and emotional problems because of the voiding disorder.

A few children with a functional voiding disorder (ie, nonneurogenic neurogenic bladder [Hinman-Allen syndrome]), have marked dysfunctional voiding and may incur significant renal damage.

Race

No known studies have shown the incidence of voiding disorders related to race.

Sex

Studies on the prevalence of voiding disorders in school children indicate that daytime urinary incontinence occurs more frequently in girls (7%) than in boys (3%).

Age

A functional voiding disorder in a neurologically and anatomically healthy child is not usually recognized before the acquisition of daytime urinary control.

Many children have a transient period of urinary urgency, occasionally with wetting accidents, when daytime continence is first being achieved. Most of these children develop normal urinary control in a relatively short period; however, some children may have persistence of urinary urgency and wetting.

Other children may have a normal voiding pattern until a UTI or an emotionally traumatic event triggers the onset of voiding symptoms.

Clinical

History

• Voiding symptoms (eg, urgency, frequency, incontinence) may be transient, intermittent, or persistent. The presence of incontinence (uncontrollable leakage of urine) is only applicable to children aged 5 years or older. Infrequent voiding, overflow incontinence, or straining to urinate are worrisome symptoms.
• Transient voiding symptoms are commonly encountered as a result of nonspecific urethritis or periurethral irritation due to vaginitis, or a UTI. Symptoms may occur without a recognized explanation.
• Symptoms caused by local factors usually clear after the irritant is removed and the local inflammation subsides. Local factors include the following:
  • Detergents in bubble bath or shampoo, which may remove protective secretions from the urethral mucosa
  • Mechanical and chemical irritation from urine-soaked underclothes
  • Local irritation due to tight undergarments
• Causes of voiding dysfunction include uninhibited detrusor contractions (overactive bladder [OAB]), dysfunction of the pelvic floor musculature (dysfunctional voiding), or decreased force of detrusor contractions (underactive bladder).
• OAB, which is also referred to as detrusor instability, urge syndrome, and urge incontinence, is the result of overactive detrusor contractions during the filling phase of micturition.
  • During voiding, normal bladder emptying occurs. This pattern of uninhibited contractions in a child with neurogenic bladder, such as occurs with myelodysplasia, is called detrusor hyperreflexia.
  • Uninhibited detrusor contractions are thought to result from a lack of inhibitory cerebral control over detrusor contractions during bladder filling. Theories on the cause of OAB have included maturation delay, prolongation of infantile bladder behavior, or abnormality of acquired toilet training habits.
  • The hallmark symptom of OAB in children is urgency, and children with this symptom can be clinically diagnosed based on the definition by the International Children’s Continence Society.³  A careful history usually reveals that the child has had ongoing urinary urgency with various posturing maneuvers in an attempt to prevent incontinence. The children are commonly evaluated because of daytime urinary incontinence or UTI.
  • Children with OAB may have a history of holding maneuvers such as standing on tiptoes, crossing of the legs, or squatting with the heel pressed into the perineum.
  • The problem may have been present since daytime urinary control began developing or can develop in a child who previously had a normal voiding pattern. The appearance of detrusor instability in a child who previously had daytime urinary control may occur after a UTI or may appear with no apparent triggering event.
  • OAB can occur in children with recurrent UTIs and is a risk factor for UTI. This voiding disorder may contribute to persistence of vesicoureteral reflux (VUR) and to the recurrence of VUR after ureteral reimplantation.
  • When chronic constipation has been present in a child with a voiding disorder, it may be the primary cause of bladder dysfunction.
• OAB and constipation are so frequently associated that the term “dysfunctional elimination syndrome” has been introduced in the literature. 
  • The effects of constipation on bladder function may be related to the direct effect of retained fecal material distending the rectosigmoid colon or due to shared neural input.
  • Constipation can be the primary or contributing cause of a voiding disorder; therefore, constipation should always be considered in the evaluation of a child with voiding symptoms.
  • Many children and families are reluctant to discuss stooling history. Often, neither the child nor the parent appears to have accurate information about stooling frequency or character.
  • Indicators of constipation include the following:
    • Infrequent passage of stools
    • Small hard stools or elongated wide-bore stools
    • Encopresis
    • Palpable stool on abdominal examination
    • Soiling in the underwear (often misinterpreted as being due to improper or careless wiping)
    • Large quantities of stool in the colon, especially the rectosigmoid area on abdominal radiography
• Giggle incontinence is the occurrence of involuntary complete bladder evacuation induced by laughter and typically appears in children aged 5-7 years.
  • Giggle incontinence can persist throughout the school years but usually improves or disappears with age. The voiding pattern is otherwise normal.
  • Episodes of incontinence may occur with giggling in some children; in others, they are induced by only vigorous laughter.
  • The etiology is unknown. Giggle incontinence is not a form of stress incontinence, nor is it due to weakness of the sphincter.
  • The authors of one study found a high incidence of daytime voiding symptoms in patients in whom they diagnosed giggle incontinence.⁴ The authors concluded that laughter induced unstable detrusor contractions in children susceptible to detrusor instability.
• Other factors may result in daytime wetting.
  • Many children aged 3-5 years tend to delay urination because of intense concentration on playing or watching television or using electronic toys. As a result, they occasionally have damp or soaked clothing. If the voiding pattern is otherwise normal, this pattern of voiding dysfunction usually subsides with increase effort towards scheduled voiding.
  • Vaginal reflux of urine from voiding in a knees-closed position can cause dampness when the child assumes an upright posture after voiding or postvoid dribbling.
  • Labial adhesions of the labia minora may cause daytime wetting due to the pooling of urine in the vagina. Treatment of the labial adhesions eliminates this cause of urinary incontinence.
  • If incontinence is persistent and continually ongoing, an ectopic ureter should be suspected and prompts evaluation by a urologist, who can often make the diagnosis based on renal ultrasound, voiding cystourethrography (VCUG), and physical examination findings.
  • The diagnosis of a neurogenic bladder is usually evident from the patient's history; occasionally, occult neuropathic bladder dysfunction can be discovered based on evaluation for urinary symptoms.
  • Daytime wetting in a previously continent child prompts the clinician to consider the possibility of sexual abuse or other trauma.
• Dysfunctional voiding involves failure to relax the urethra and pelvic floor muscles with voiding and is caused by overactivity of the urethral sphincter or pelvic floor muscles during the voiding phase of the micturition cycle. This pattern of voiding incoordination in a child with a neurogenic bladder is called detrusor sphincter dyssynergia.
  • Although the etiology is unknown, it is thought to reflect a deviation in the normal development of urinary control. As daytime urinary control is achieved, many children have a transitional phase in which pelvic withholding maneuvers are used to prevent incontinence. Most children then develop a pattern of coordinated voiding that make it unnecessary to contract the external sphincter to prevent incontinence. Few children who have a delay in establishing cerebral control over detrusor contractions continue to use pelvic-tightening maneuvers; over time, these appear to become involuntary. Others have suggested that this pattern of dysfunction of the pelvic floor muscles is a consequence of overtraining of the urinary bladder.
  • Dysfunctional voiding symptoms vary from mild daytime frequency and postvoid dribbling to daytime and nighttime wetting, urgency, urge incontinence, pelvic holding maneuvers, and UTIs. In the most severe form, children with dysfunctional voiding resemble those with neurogenic bladder or anatomic bladder outlet obstruction.
  • Children with this condition can have increased intravesical pressure upon voiding, incomplete bladder emptying, UTIs, persistent VUR, dilatation of the upper tract (hydronephrosis), or, rarely, renal damage.
  • Evaluation of patients with suspected dysfunctional voiding should be performed by a urologist, and may include voiding cystourethrography, urinary tract ultrasonography, urodynamic studies, and, in some instances, MRI of the lumbosacral spine to rule out a neurologic etiology.
• Underactive bladder syndrome describes children who void infrequently.
  • Infrequent voiding is diagnosed if a child voids 3 or fewer times in 24 hours or if a child does not void for 12 hours. These children may also use abdominal straining to void.
  • The pattern of infrequent voiding is clinically important. The detrusor muscle may be hypocontractile, and voiding may be accomplished by increased intra-abdominal pressure (abdominal straining) as the driving force to expel urine. The diagnosis may be confirmed by urodynamic study. 
  • This voiding pattern may be a variant of normal. However, if identified, the voiding pattern should be treated with behavioral modification of the child's voiding regimen.

Physical

No notable findings are noted upon physical examination of a child with voiding dysfunction; however, a thorough examination should be performed to evaluate for other sources of voiding symptoms.

• Perform a careful physical examination to rule out an abnormality of the lumbosacral area that suggests occult spinal dysraphism, which includes a sacral dimple or tuft of hair, dermal vascular malformations, a small lipomeningocele, or absence of the gluteal cleft with flattened buttocks.
• The neurologic examination should include assessment of motor strength, deep tendon reflexes, perineal sensation, gait, and coordination.
• Carefully examine the genitalia to be certain they are normal. Look for labial adhesions in girls and meatal stenosis in boys. In girls, the genitalia should be examined evaluate for sexual abuse, as one study reported that 6% of patients evaluated for voiding dysfunction had a history of sexual abuse (89% of that group was female).⁵ Rashes in the perineal or genital areas may indicate fungal infections that result from chronic wetness.

Causes

• Causes of voiding dysfunction include uninhibited detrusor contractions (OAB), dysfunction of the pelvic floor musculature (dysfunctional voiding), or decreased force of detrusor contractions (underactive bladder).

• Search for CME/CE on This Topic »

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