Normal Voiding and Toilet Training

The fetus voids by reflex bladder contraction in concert with simultaneous contraction of the bladder and relaxation of the sphincter. Urine storage consists of sympathetic and pudendal nerve-mediated inhibition of detrusor contractile activity accompanied by closure of the bladder neck and proximal urethra with increased activity of the external sphincter. The infant has coordinated reflex voiding as often as 15-20 times/day. Over time, bladder capacity increases. In children up to the age of 14 yr, the mean bladder capacity in ounces is equal to the age (in yrs) plus 2.

At 2-4 yr, the child is developmentally ready to begin toilet training. To achieve conscious bladder control, several conditions must be present: awareness of bladder filling; cortical inhibition (suprapontine modulation) of reflex (unstable) bladder contractions; ability to consciously tighten the external sphincter to prevent incontinence; normal bladder growth; and motivation by the child to stay dry. The transitional phase of voiding refers to the period when children are acquiring bladder control. Girls typically acquire bladder control before boys, and bowel control typically is achieved before bladder control.

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.

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.)

Figure 537-2 Bristol Stool Chart for evaluating bowel function.

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.

Figure 537-3 Spinning top deformity. Voiding cystourethrogram demonstrating dilation of the urethra with distal urethral narrowing and contraction of the bladder neck.

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.

Non-Neurogenic Neurogenic Bladder (Hinman Syndrome)

Hinman syndrome is a more serious but less common disorder involving failure of the external sphincter to relax during voiding in children without neurologic abnormalities. Children with this syndrome, also called detrusor-sphincter dyssynergia, typically exhibit a staccato stream, day and night wetting, recurrent UTIs, constipation, and encopresis. Evaluation of affected children often reveals vesicoureteral reflux, a trabeculated bladder, and a decreased urinary flow rate with an intermittent pattern (Fig. 537-4). In severe cases, hydronephrosis, renal insufficiency, and even end-stage renal disease can occur. The pathogenesis of this syndrome is thought to involve learning abnormal voiding habits during toilet training; the syndrome is rarely seen in infants. Urodynamic studies and magnetic resonance imaging of the spine are indicated to rule out a neurologic cause for the bladder dysfunction.

Figure 537-4

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