Bedwetting in children

By K.M. LEW

Most children can control voiding by the age of five years. However, incontinence can occur in about 1% of those aged 18 years. 

      THE kidneys produce urine, which passes through the ureters to enter the bladder, a hollow and distensible organ that sits on the pelvic floor. The stored urine exits the body through the urethra, which is a tubular structure. This act (voiding) involves muscles, nerves, the spinal cord and the brain.

      The bladder has two types of muscles. The detrusor muscle stores urine and contracts when emptying the bladder. The bladder sphincter is a circular group of muscles found at the bottom of the bladder. It automatically contracts to retain urine in the bladder and relaxes when the detrusor muscle contracts (when the urine gets into the urethra).

      When the pelvic floor muscles contract, urine is held back in the bladder.

      The newborn’s bladder fills up to a certain set level at which the bladder muscle contracts automatically, leading to voiding. As the newborn grows, his or her nervous system matures. The brain starts receiving messages from the filling bladder through the spinal cord and also sends messages to the bladder.

      Eventually, the child is able to stop the bladder from voiding automatically until the child decides when and where to void.

      When the control mechanisms are immature or fails, it results in bedwetting (incontinence). Most children are able to control voiding by the age of five years. However, incontinence can occur in about 1% of those aged 18 years. Incontinence is twice as common in males as compared to females.

There are certain medical terms used to describe incontinence in children:

      > Primary enuresis is incontinence in someone who has never been dry for at least six months

      > Secondary enuresis is incontinence that begins after at least six months of dryness

      > Nocturnal enuresis is incontinence which occurs during sleep. It is also called night time incontinence

      > Diurnal enuresis is incontinence which occurs when awake. It is also called daytime incontinence

      There are several causes of bedwetting in children and they vary from the simple to the complex.

Causes 

      Nocturnal enuresis is more common than diurnal enuresis after the age of five years. The causes of nocturnal enuresis are not well clarified yet. Most cases result from a variety of causes that include slower physical development, an increased production of urine at night, a lack of ability to recognise bladder filling when asleep, and, occasionally, anxiety.

      Nocturnal enuresis between the ages of five and 10 years due to a smaller bladder capacity usually disappears gradually as the bladder capacity increases.

      The body produces a hormone called antidiuretic hormone (ADH) which reduces the production of urine. As less ADH is produced at night, the need to void is less. Sometimes the body does not produce sufficient ADH at night, leading to the production of more urine. If a child does not sense the increased volume of urine in the bladder and awakens to void, bed wetting will result.

      Anxiety has been suggested as a cause of bedwetting in children between two and four years of age when they have yet to achieve total control of their bladders. Anxiety after the age of four years can also lead to nocturnal enuresis after the child has been dry for six months or more. The anxiety-causing events include angry parents or relatives, birth of a sibling, and unfamiliar social situations.

      Incontinence itself can cause anxiety. Diurnal enuresis can cause anxiety that leads to nocturnal enuresis.

A strong family history of bedwetting is suggestive of genetic causes. Studies have reported that a child has an 80% chance of bedwetting if both parents had been bed wetters.

      There is a small group of children who have physical abnormalities in their urinary tract which lead to incontinence, e.g. a blocked bladder or urethra, and nerve damage associated with spina bifida, which is a birth defect of the spinal cord.

      Diurnal enuresis is less common than nocturnal enuresis and usually disappears earlier than nocturnal enuresis.

      An overactive bladder is one of the causes of diurnal enuresis. When the detrusor muscle of the bladder contracts strongly, the bladder sphincter may be unable to prevent voiding. This occurs frequently when there is a urinary tract infection (UTI), which is more common in girls because of their short urethras.

      Many children who have diurnal enuresis have abnormal habits, the most common being infrequent voiding. They ignore the feeling of a full bladder and do not void for long periods for various reasons, e.g. not wanting to use the toilets at school. As the bladder is overfilled, the urine leaks. Such children are prone to UTIs, which in turn leads to an overactive bladder.

      The causes of nocturnal enuresis may interact with infrequent voiding to lead to diurnal enuresis. These causes include small bladder capacity, anxiety, and physical abnormalities of the urinary tract. Pressure from a distended lower bowel, when a child has constipation, and caffeine-containing foods or drinks, that increase urine output, are other contributory causes.

Management

      There are various management modalities available. They include no treatment, bladder training, medicines, dietary modification, and moisture alarms.

      Most cases of bedwetting in children resolve spontaneously without any treatment as the child grows up. It has been estimated that the incidence of bed wetting reduces by 15% annually after the age of five years.

      The body’s changes with the passage of time include an increase in bladder capacity, resolution of an overactive bladder, the normal production of ADH, the resolution of anxiety provoking events, and the child learning to respond to the signals that it is time to void.

      Bladder training involves exercises that help to strengthen and co-ordinate the bladder’s muscles. The child learns to anticipate the need to void and to control oneself when there is no toilet nearby.

      The methods used for nocturnal enuresis include determining bladder capacity, drinking less before bed time, and having a routine for waking.

      The methods used for diurnal enuresis include voiding according to a schedule, avoiding caffeine containing foods or drinks, and relaxing the muscles. There is, however, no guarantee of success with these bladder training methods.

      There are medicines available to treat bed wetting. ADH levels can be increased with desmopressin, and an overactive bladder controlled with anticholinergics.

      The medicine, imipramine, which acts on the brain and bladder, is used for short term treatment of nocturnal enuresis.

      Moisture alarms awaken a person when voiding starts. The device has a water-sensitive pad that is placed in the pajamas and is connected to a battery-driven control. An alarm goes off when moisture is detected on the pad. The child has to wake up when the alarm goes off and go to the washroom to void.

      The use of such alarms may require another person to sleep in the same room as the child to awaken him or her.

      Bedwetting is common in young children. It resolves spontaneously in most instances. The management modalities include no treatment, bladder training, medicines, dietary modification, and moisture alarms. Anyone whose child has bedwetting would benefit from a reassuring discussion with the doctor.