Family doctor

What is it?

Enuresis means bedwetting and is a common problem in childhood. The incidence is between 12-15 percent for five and six year olds, 5 percent for 10 year olds and 1 percent for 15 year olds.

The male to female ratio is equal in five year olds but enuresis is more common in boys by the age of 10, with a male to female ratio of 1.5:1 at 10 years.

There may be a lower incidence of enuresis in Chinese children. One Hong Kong study found 3.5 percent of five year olds suffered from it. Otherwise, the incidence is similar in various studies around the world.

Children with enuresis fall into two categories:

• Large nocturnal urine output with normal bladder volume.

• Normal or large nocturnal urine output with small functional bladder volume.

Less than five percent of cases have a structural abnormality of the urinary tract. These cases may be suspected by daytime wetting, poor urinary stream and the presence of a urinary tract infection.

Enuresis can be associated with chronic constipation and occasionally linked with upper airway obstruction and sleep apnoea.

There is often a family history of the problem. About 60 percent of affected children have an affected parent. Recent studies are searching for possible genes which may cause or predispose children to the condition. There is some evidence of a link between the condition and three genes on chromosome 13q, 12q, and 22q (q means long arm of that chromosome).

Although strong genetic predisposition is evident, this probably explains about 70 percent of the risk. Other factors are still uncertain.

How is enuresis diagnosed?

Establish whether the child has abnormal daytime voiding (urinating) pattern. This includes establishing frequency, urgency, urinary stream, daytime wetting, and symptoms of urinary tract infection currently or in the past.

The doctor will examine the child's abdomen for evidence of constipation or enlarged bladder after voiding. They will also examine blood pressure, spine, lower limbs, external genitalia - foreskin and urinary meatus (hole at tip of penis) in boys, and posterior labial fusion in girls.

Samples of the child's urine will be sent to a laboratory for testing.

An ultrasound will be ordered only if there are clinical features in addition to nocturnal enuresis such as daytime wetting and urinary tract infections.

There is currently no genetic or other predictive test to establish whether a particular child is predisposed to enuresis.

Diagnosis is only made in children aged five years or older. Children below this age fall within normal variations of development.

What can be done?

Enuresis can resolve spontaneously. The spontaneous resolution rate for enuresis is 15 percent per annum. However, there is no reliable way of predicting whether an individual child will become dry in the next 12 months.

Behavioural method

The enuresis alarm (bed buzzer) method has an established efficacy of about 70-80 percent when used correctly.

This method requires a reliable alarm system with a low 'false alarm' rate. It is usually best used in a child mature enough to want to become dry and who can cooperate with the treatment method - usually 7 years or older.

There are a few studies which have shown some 5-6 year old children can become dry with the enuresis alarm method.

The relapse rate in children successfully treated with the enuresis alarm is low, about 10-15 percent.

The successful application of the enuresis alarm method takes several weeks, often 6-8 weeks to be effective.

Medication

Desmopressin is an analogue of antidiuretic hormone. It has the effect of greatly reducing the urine production rate, over a period of 8-12 hours. It is administered by a nasal spray. It is about 75 percent effective. However, it is effective only on the night it is administered.

There is no convincing evidence that desmopressin has any favourable effect on the natural history of the condition, i.e. it does not increase the recovery rate above 15 percent per annum.

It is not recommended for long-term use. It is very helpful for short-term use for special occasions like school camps, sleep overs, etc.

It is a very safe treatment when used in accordance with the advised precautions - the most important being not to have further drinks until the next morning after the medication has been administered.

A small group of children with enuresis may be helped by the use of oxybutynin, an anticholinergic bladder muscle relaxant, especially those children who have a small functional bladder capacity. These children have daytime urgency and frequency, but even if the medication improves their daytime symptoms, it may not stop their bedwetting.

An earlier treatment for enuresis was the use of imipramine, which also has a mild anticholinergic effect (allows the bladder to fill to a bigger volume) and may also enable the child to wake more easily when the bladder is full. Imipramine is not often used for the treatment of enuresis now, it can be regarded as a second-line therapy.

Other methods of management have no proven efficacy, these include:

• Fluid restriction before bed
• Parent waking the child during the night for toileting
• Punishment
• Encouragement e.g. star charts

Prognosis

Most children do eventually cease to have bedwetting, but there is a small incidence (less than 1 percent) in the adult population.

There are no convincing studies showing psychological or behavioural disturbances have led to enuresis, but persistent enuresis can lead to an unhappy, withdrawn child. For this reason many authorities recommend intervention to treat the condition and reduce this risk, but there are few if any prospective studies which have proven this benefit.

Seeking help:

Don't hesitate to discuss possible treatments with your doctor if needed.

The New Zealand Continence Association has a freephone number for people to call for information and support. Ph 0800 650 659.