Voiding Dysfunction

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Chapter 537 Voiding Dysfunction

Diurnal Incontinence

Daytime incontinence not secondary to neurologic abnormalities is common in children (Chapter 21.3). At age 5 yr, 95% have been dry during the day at some time and 92% are dry. At 7 yr, 96% are dry, although 15% have significant urgency at times. At 12 yr, 99% are dry during the day. The most common cause of daytime incontinence is an overactive bladder. Table 537-1 lists the causes of diurnal incontinence in children.

Important points in the history include the pattern of incontinence, including the frequency, the volume of urine lost during incontinent episodes, whether the incontinence is associated with urgency or giggling, whether it occurs after voiding, and whether the incontinence is continuous. The frequency of voiding and whether there is nocturnal enuresis, a strong, continuous urinary stream, or sensation of incomplete bladder emptying should be assessed. A diary of when the child voids and whether the child was wet or dry is helpful. Other urologic problems such as urinary tract infections (UTIs), reflux, neurologic disorders, or a family history of duplication anomalies should be assessed. Bowel habits also should be evaluated, because incontinence is common in children with constipation and/or encopresis. Diurnal incontinence can occur in girls with a history of sexual abuse. Physical examination is directed at identifying signs of organic causes of incontinence: short stature, hypertension, enlarged kidneys and/or bladder, constipation, labial adhesion, ureteral ectopy, back or sacral anomalies (see Fig. 536-4), and neurologic abnormalities.

Assessment tools include urinalysis, with culture if indicated; bladder diary (recorded times and volumes voided, whether wet or dry); postvoid residual urine volume (generally obtained by bladder scan); Dysfunctional Voiding Symptom Score (Fig. 537-1); Bristol Stool Form Score (Fig. 537-2); and uroflow with or without EMG (noninvasive assessment of urinary flow pattern and measurement of external sphincter activity). Imaging is performed in children who have significant physical findings, a family history of urinary tract anomalies or UTIs, and those who do not respond to therapy appropriately. A renal ultrasonogram with or without a voiding cystourethrogram (VCUG) is indicated. Urodynamics should be performed if there is evidence of neurologic disease and may be helpful if empirical therapy is ineffective.

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Figure 537-1 Dysfunctional Voiding Score questionnaire.

(From Farhat W, Bagli DJ, Capolicchio G, et al: The dysfunctional voiding scoring system: quantitative standardization of dysfunctional voiding symptoms in children, J Urol 164:1011–1015, 2000.)

Overactive Bladder

Children with an overactive bladder typically exhibit urinary frequency, urgency, and urge incontinence. Often a girl will squat down on her foot to try to prevent incontinence (termed Vincent’s curtsy). The bladder in these children is functionally, but not anatomically, smaller than normal and exhibits strong uninhibited contractions. Approximately 25% of children with nocturnal enuresis also have symptoms of an overactive bladder. Many children indicate they do not feel the need to urinate, even just before they are incontinent. In girls, a history of recurrent UTI is common, but incontinence can persist long after infections are brought under control. It is not clear in these cases if the voiding dysfunction is a sequela of the UTIs or if the voiding dysfunction predisposes to recurrent UTIs. In girls, voiding cystourethrography often shows a dilated urethra (“spinning top deformity,” Fig. 537-3) and narrowed bladder neck with bladder wall hypertrophy. The urethral finding results from inadequate relaxation of the external urinary sphincter. Constipation is common and should be treated, particularly with any child with Bristol Stool Score 1 or 2.

The overactive bladder nearly always resolves, but the time to resolution is highly variable, sometimes not until the teenage years. Initial therapy is timed voiding, every 1.5-2.0 hr. Treatment of constipation and UTIs is important. Another treatment is biofeedback, in which children are taught pelvic floor exercises (Kegel exercises), because there is evidence that daily performance of these exercises can reduce or eliminate unstable bladder contractions. Biofeedback also may include periodic uroflow studies with sphincter electromyography to be certain that the pelvic floor relaxes during voiding, and assessment of postvoid residual urine volume by sonography. Anticholinergic therapy with oxybutynin chloride, hyoscyamine, or tolterodine reduces bladder overactivity and may help the child achieve dryness. Treatment with an α-adrenergic blocker such as terazosin or doxazosin can aid in bladder emptying by promoting bladder neck relaxation; α-adrenergic blockers also have mild anticholinergic properties. If pharmacologic therapy is successful, the dosage should be tapered periodically to determine its continued need. Children who do not respond to therapy should be evaluated urodynamically to rule out other possible forms of bladder or sphincter dysfunction. In refractory cases, sacral nerve stimulation (Interstim) is a surgical procedure that has shown promise.