Enuresis
Enuresis (pronounced "en-you-ree-sis") refers to the involuntary emptying of the bladder. When it occurs during sleep ("bedwetting"), it is called nocturnal enuresis. When it occurs during the day, while awake, it is known as diurnal enuresis. Nocturnal enuresis is the most common disorder of bladder function in children; the remainder of this discussion will use the term enuresis to mean nocturnal enuresis.
Because girls achieve bladder control somewhat earlier than boys, the usual definition states that continued wetting in girls beyond the age of five years, and in boys beyond the age of six years, constitutes enuresis.
What causes enuresis?
Researchers in Hong Kong (published in the New England Journal of Medicine, May 29, 2008 issue) suggest that the bladders of children who wet the bed are constantly sending signals to arouse the brain, which results in a light sleep. But paradoxically, that very overstimulation suppresses the children's ability to awaken completely, and as a result they wet the bed.
Read more about the study here.
In children with the most common type (the non-organic type), the exact cause is not known. However, most physicians believe that it is due to delayed maturation of .
In a small number of children, the cause of enuresis is organic; that is, it may be a temporary problem associated with a urinary tract infection in which the enuresis subsides after the infection is successfully treated. Or, in an even smaller number of children, the enuresis is caused by an anatomic problem of the urinary tract. If the urologist suspects this, it may be necessary to do additional tests, including ultrasound or x-rays of the kidneys and bladder.
But the vast majority of children with enuresis do not have underlying urinary tract disease and, therefore, have the non-organic or functional type. This accounts for at least 95% of cases of enuresis.
How common is enuresis?
Most children under the age of three years have enuresis. However, by the age of five years, up to 85% of children have achieved bladder control. By age 12 years, up to 95% of children have nighttime bladder control. For this reason, enuresis is generally not diagnosed or treated in children younger than five years of age. Children between the ages of three and five years with bedwetting, if otherwise well, are considered to have delayed maturation of bladder function.
Bladder function
Since the kidneys produce urine continuously, the bladder serves as a storage reservoir for urine. The process of bladder emptying (also referred to as "voiding") is intermittent. In infants, voiding is automatic and may be as frequent as every two to three hours. After bladder control is mastered, bladder emptying occurs less frequently and is under voluntary control. During the filling phase the bladder is relaxed and the outlet of the bladder is shut tightly by contraction of a sphincter muscle (a circular band of muscle). When the bladder is fully distended by urine, contraction of the muscle in the wall of the bladder is triggered. This contraction is normally coordinated with a simultaneous relaxation of the sphincter at the outlet of the bladder. When this sphincter muscle relaxes, the urine is propelled out by the contraction of the bladder muscle. Normal bladder function results in complete emptying.