Pediatric Examination and Board Review (218 page)

(A) autosomal recessive disorder

(B) autosomal dominant disorder

(C) X-linked recessive disorder

(D) all of the above

(E) none of the above

12.
An enuresis gene has been identified on

(A) chromosome 12

(B) chromosome 13

(C) chromosomes 8 and 22

(D) all of the above

(E) there is no enuresis gene

13.
Primary nocturnal enuresis can be associated with

(A) nocturnal detrusor hyperactivity

(B) nocturnal polyuria

(C) poor arousal-from-sleep mechanism

(D) all of the above

(E) A and B

14.
The spontaneous annual resolution rate of monosymptomatic nocturnal enuresis is

(A) 25%

(B) 30%

(C) 15%

(D) 35%

(E) 40%

15.
Functional bladder capacity in a normal child in ounces is usually

(A) age + 2

(B) age + 8

(C) age + 6

(D) age + 4

(E) age + 9

16.
Nocturnal detrusor hyperactivity occurs in

(A) 50% of all children with nocturnal enuresis

(B) 10% of all children with nocturnal enuresis

(C) 60% of all children with nocturnal enuresis

(D) 30% of all children with nocturnal enuresis

(E) 5% of all children with nocturnal enuresis

17.
Enuresis may be associated with all of the following except

(A) food allergies

(B) constipation

(C) obstructive sleep apnea

(D) ADHD (attention deficit hyperactivity disorder)

(E) asthma

ANSWERS

1.
(B)
Daytime bladder control is usually achieved by 2 years when the child learns to inhibit unwanted detrusor contractions during the day. Nighttime bladder control is usually achieved by 5 years in girls and 6 years in boys. Late achievement of nighttime control in boys is attributed to mild developmental lag in boys. Enuresis needs to be differentiated from urinary incontinence. Enuresis is defined as involuntary discharge of urine without any underlying anatomic abnormality, whereas urinary incontinence is involuntary discharge of urine associated with an underlying structural abnormality.

2.
(B)
Three groups of patients with primary nocturnal enuresis are now described:

1. Patients with a pure arousal mechanism problem

2. Patients with a nighttime arousal problem and daytime detrusor hyperactivity

3. Patients with a nighttime arousal problem with nighttime polyuria or nocturia

Monosymptomatic nocturnal enuresis with arousal mechanism problem is a result of failure of the locus ceruleus in the rostral pons to awaken the child in response to a full bladder. These children have normal voiding otherwise.

The term
nonmonosymptomatic nocturnal enuresis
refers to these same children who in addition to arousal mechanism problems have coexistent daytime symptoms of urgency or voiding dysfunction because of detrusor hyperactivity and/or nocturnal polyuria.

Enuresis is “primary” if the child has never had a more than 6-month period of dry nights and “secondary” if the child, after being dry for more than a 6-month period, starts to have bedwetting again.

3.
(B)
The prevalence of primary nocturnal enuresis is 10-15% at 6 years of age. There is a 10-15% spontaneous remission rate annually every year leading to a prevalence of 5% at 10 years of age and 1% at 15 years of age and beyond. Thus it is important to remember that 1% of adults continue to have the problem.

4.
(D)
All of these conditions can cause bedwetting in a child. However, this patient is a girl, and posterior urethral valves are seen almost exclusively in boys.

Differential diagnosis includes new-onset diabetes mellitus, diabetes insipidus, spina bifida occulta, obstructive sleep apnea, urinary tract infection, vulvovaginitis, posterior urethral valves in boys, chronic renal failure, and central nervous system tumors.

Clinical examination and history should be specifically focused on looking for evidence of constipation, abdominal masses, palpable bladder, high plantar arch, or hammer toes with asymmetric atrophy of lower extremities suggestive of spina bifida occulta, as well as examination of spine and genitalia.

5.
(E)
In this patient the history is very suggestive of primary nocturnal enuresis with daytime detrusor hyperactivity and there is no history of UTIs. Therefore, none of these investigations are indicated. Generally a urinalysis, urine culture, complete blood count, and assessment of renal function with serum BUN, creatinine, and an electrolyte determination is sufficient to rule out UTI and renal functional impairment. The sacral dimple without a hairy patch may be a normal finding in such a patient. However, a sacral dimple with a hairy patch may also be associated with spina bifida occulta, which could potentially cause bladder dysfunction as a result of a tethering of the spinal cord with consequent enuresis. A sacral dimple with a hairy patch should be investigated with an MRI to look for spina bifida occulta.

6.
(A)
In primary enuresis, if one parent had enuresis as a child, the risk of the offspring having enuresis is 43% if the father was affected or 44% if the mother was affected as a child. The risk is 77% if both parents were affected during childhood. Enuresis is more common in boys and first-born children.

Multiple factors including genetic factors may be responsible for primary nocturnal enuresis. Evidence of genetic susceptibility comes from studies of familial incidence, twin studies, and molecular genetics with linkage analysis. Twin studies show 70% concordance for monozygotic twins and 31% concordance for dizygotic twins. Molecular genetics with linkage analysis has revealed a polymorphism with localization of genes for enuresis on several different chromosomes. Earlier studies localized the gene to the long arm of chromosome 13 (D13S 291 and D13S 263) and the long arm of chromosome 12 (D12S 80 and D12S 43) in 2 different families.

7.
(D)
Both oxybutynin and tolterodine are anticholinergic drugs that help inhibit unwanted detrusor contractions and increase urethral sphincter tone. Therefore they can potentially help this child’s symptoms. It is important to keep in mind that this child’s constipation should also be treated because both oxybutynin and tolterodine, due to their anticholinergic effect, can make constipation worse. Imipramine has been used to treat primary nocturnal enuresis. It is reported to work through its effect on the arousal mechanism, a decrease in nighttime urinary sodium excretion, a consequent decrease in nocturia, and a weak anticholinergic effect. However its use is limited because of possible significant side effects and a high relapse rate of enuresis once the treatment is stopped. In this patient who has symptoms of detrusor hyperactivity, imipramine would not be a treatment of choice.

8.
(B)
Surprisingly, punishment is still used by a fair number of parents for wetting the bed and has obvious negative consequences. Demystification in the presence of the child with the explanation to the parents that the child is not intentionally wetting the bed has a 15-25% therapeutic effect on the child’s enuresis. Fluid restriction and voiding before going to bed may help augment the effect of other therapeutic modalities. In this patient an enuresis alarm in combination with oxybutynin could prove to be effective provided the child and the parents are motivated to try the enuresis alarm program. A behavioral program is used with the alarm.

9.
(D)
The enuresis alarm program is the most effective treatment for a child with primary nocturnal enuresis caused by pure arousal mechanism problem with a success rate higher than 90% and a low incidence of relapse compared with pharmacologic therapies. Imipramine, which is seldom used now, has a response rate of 50% with a relapse rate of almost 100% after discontinuation; DDAVP has a response rate of 76% but a relapse rate of 60-100% after discontinuation.

10.
(E)
As mentioned, primary nocturnal enuresis can be divided into these 3 groups.

11.
(B)
Primary nocturnal enuresis can be inherited as an autosomal dominant disorder.

12.
(D)
Genes mediating enuresis have been reported at several loci. Initial molecular genetic methods such as linkage analysis showed foci on chromosomes 13 and 12 in different families. Other studies subsequently showed enuresis gene loci on chromosomes 8 and 22 in other families.

13.
(D)
Primary nocturnal enuresis is now classified into monosymptomatic nocturnal enuresis with an isolated arousal disorder or non-monosymptomatic nocturnal enuresis where an arousal disorder may be associated with reduced bladder capacity or nocturnal detrusor hyperactivity and/or nocturnal polyuria.

14.
(C)
Monosymptomatic nocturnal enuresis has an annual spontaneous resolution rate of 15%. Thus for any treatment to be proven effective for enuresis, the rate of resolution of symptoms with the treatment must be higher than this background rate.

15.
(A)
One formula to estimate bladder capacity in children was described by Berger and coworkers and Koff: Bladder capacity (in ounces) = Age (yr) + 2, up to 15 years of age when the adult bladder capacity is achieved.

16.
(D)
Nocturnal detrusor hyperactivity is reported to occur in 30% of patients with nocturnal enuresis and is one reason for failure to respond to vasopressin. These patients may need other pharmacologic agents such as oxybutynin or tolterodine to treat detrusor hyperactivity and to improve bladder capacity.

17.
(E)
Food allergies have been reported to lead to enuresis in 10% of affected patients. Some of these children are reported to benefit from elimination of certain foods from the diet, such as citrus fruit, juices, foods high in caffeine and sugar, dairy products, artificially colored drinks, and chocolate. Constipation can potentially interfere with the bladder function as a result of pressure from constipated stools in the sigmoid colon. Obstructive sleep apnea can cause enuresis (hypoxia and increased atrial natriuretic peptide secretion, leading to nocturia, are the proposed mechanisms). There is a higher incidence of enuresis in children with ADHD.

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