Bedwetting: Nocturnal Enuresis - When should you treat?

Bed wetting or nighttime incontinence, otherwise known as "nocturnal enuresis," refers to the involuntary passage of urine during sleep. "Enuresis" is the involuntary discharge of urine after the age by which bladder control should have been established.

The most common form of enuresis is nighttime bedwetting or nocturnal enuresis. Nocturnal enuresis is classified as

• Primary (no prior period of sustained dryness) or
• Secondary (recurrence of nighttime wetting after 6 months or longer of dryness).

For the diagnosis of nocturnal enuresis to be established, a child aged five or older should have two or more bedwetting episodes per month, and a child older than six years of age should have one or more bedwetting episode per month.

Nocturnal enuresis has a spontaneous cure rate of approximately 14% per year; however up to 3% of children remain enuretic as adults.

Although this condition is pathologically benign, it can have serious social and psychological repercussions for the sufferer including affects on self esteem, school success, parental disapproval and even sexual activity in later life.

At What Age Is Bed Wetting Abnormal? 

Bladder control is usually established in children by the age of 5 years. Most children are toilet trained for daytime between the ages of 2 1/2 to 5 years, and night training usually follows around six months later.

The International Children’s Continence Society defines nocturnal enuresis as:

• A child five to six years old with two or more bedwetting episodes per month
• A child over six years old with one or more bedwetting episodes per month

However, most management strategies are aimed at children aged seven years or older, as this is when bedwetting is usually considered to be a problem by both the child and their family.

What Causes Bed Wetting?

Delayed functional maturation. The most commonly accepted cause of nocturnal enuresis, but also the most difficult to prove, is delayed functional maturation of the central nervous system, which reduces the child's ability to inhibit bladder emptying at night. It is probably reflected in the higher rate of bedwetters among developmentally delayed children and those with low birth weights.

Genetic predisposition. The evidence for genetic predisposition is strong, but the exact mechanism for the inheritance of nocturnal enuresis is unknown. If both parents have a history of enuresis, 70% of their children will also have enuresis. If only one parent had enuresis, 40% of their children will be affected, and only 15% of children will have enuresis if neither parent had that condition.

High sleep arousal thresholds. Parents have consistently reported that the enuretic child is more difficult to awaken than the nonenuretic children in the same family. These parental perceptions often were disregarded, but recent studies have shown that this proposition may have some scientific basis, and that these children may have high sleep arousal thresholds. In most children, arousability from sleep improves with central nervous system maturation.

Nocturnal polyuria.The most controversial etiologic theory for nocturnal enuresis is nocturnal polyuria (excessive nocturnal urine production) due to insufficient nocturnal production of anti-diuretic hormone (ADH). Normally, the level of ADH increases during the night, causing the body to produce a smaller total volume of more concentrated urine during sleep. There are studies which suggest that some bedwetting children do not produce enough ADH at night. This diurnal change may not be seen until about 10 years of age, and inadequate nighttime ADH levels may contribute to increased nocturnal urine production in children with nocturnal enuresis.

Bladder problems. Studies attempting to establish bladder problems as the cause of nocturnal enuresis have been contradictory. Extensive urodynamic testing has shown that bladder function is normal in children with nocturnal enuresis. However, two investigations found that while real bladder capacity is identical in children with and without nocturnal enuresis, there may be decreased functional bladder capacity (the volume at which the bladder empties itself) in those with enuresis.

Psychological. Nocturnal enuresis was once thought to be a psychological condition. It now appears that psychological problems are the result of enuresis and not the cause. Children with nocturnal enuresis have not been found to have an increased incidence of emotional problems. For most children, bed wetting is not an act of rebellion. However, secondary nocturnal enuresis may be related to stressors at home or school.

How Is Bed Wetting Treated?

Non-pharmacologic therapy

The most critical aspect of treatment is reassurance for the child, who may experience low self-esteem. An important factor in any paediatric treatment is the child's motivation and acceptance. Parents must also support the child and the treatment program for maximal efficacy. Behavioural therapy includes dry-bed training and classic conditioning therapy using an enuresis alarm system.

Dry-bed training. This involves waking the child on a progressive schedule of decreasing intervals over several nights, having the child change pyjamas and bedding if wet or walk to the toilet if voiding is needed. Although a high cure rate is reported with this technique, it is a more time- and labour-intensive process than most families are willing to undertake.

Enuresis alarms. These have the highest overall cure rate for nocturnal enuresis of any available treatment. The concept of using an alarm that emits a sound when a child wets the bed was first introduced in 1938. Compared with other behavioural or pharmacologic treatments, the bed-wetting alarm has a higher success rate (75%) and a lower relapse rate (41%). The alarm appears to work by negative reinforcement or avoidance. The alarm is sounded to wake the child during voiding; the child gets out of bed and finishes voiding in the toilet or holds urine until later.

For resolution of nocturnal enuresis, the bed-wetting alarm may need to be used for up to 15 weeks. Unfortunately, treatment with bed-wetting alarms has a dropout rate of 10 to 30 percent. The disadvantage of enuretic alarms is that they require a high level of motivation and cooperation from the child and the family for at least 3 weeks and for as long as 4 to 6 months. It is recommended that the child continue to wear the alarm until dry at night for 4 weeks, rather than for a shorter dry period. Two types of alarm systems available include one which comprises a large pad which is placed in the bed and triggers a loud alarm when liquid comes into contact with it. The second involves a personal alarm which is either clipped onto the child’s underpants or a pad placed inside the child’s underpants, with any liquid triggering the alarm.

Pharmacologic therapy

Desmopressin (DDAVP) is a synthetic analog of anti-diuretic hormone and acts by reducing the urine production, thereby increasing water retention and urine concentration. The effect usually lasts 6 to 12 hours. Desmopressin is listed on the PBS and is available in a nasal-spray pump or oral tablets.  Desmopressin is safe if used correctly, and side effects are rare. The cure rate is between 25% and 50%, and the relapse rate after discontinuance of desmopressin is 90%.

Imipramine (Tofranil) is a tricyclic antidepressant that offers two beneficial physiologic effects: a direct relaxation action on bladder tone, and a decrease in the depth of sleep during the last third of the night. Successful management has been reported to range between 20% and 50%.

Unfortunately, discontinuance of use of imipramine usually leads to recurrent incontinence, and the resolution rate of nocturnal enuresis does not differ from that in untreated control subjects. Side effects are uncommon, and include dry mouth, nervousness, insomnia, and mild gastrointestinal disturbances. A great concern with imipramine is the possibility of overdose. An adult should dispense this medication, and the medication should be kept out of the reach of toddlers. Severe overdoses can cause myocardial effects (arrhythmias and conduction blocks) and hypotension.

Oxybutynin (Ditropan), an anticholinergic medication, has a role in reducing uninhibited bladder contractions. This medication may be helpful to those children with nocturnal enuresis who also present with daytime frequency, urgency, and/or incontinence. In these children, success rates of 90% have been reported; however, anticholinergics are rarely beneficial for children with exclusive nocturnal enuresis. 

Combined treatment of desmopressin with enuresis alarms is superior, particularly for nonresponders of each individual treatment. Both treatments are started at the same time – the rapid action of desmopressin is believed to facilitate the patient’s adaptation to the alarm. After six weeks, the desmopressin is discontinued, while the alarm treatment is continued until the patient is completely dry. Compared with either therapy alone, the combination has been found to be particularly effective in patients with frequent wetting and behavioural problems.

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