Many causes of bedwetting have been proposed by researchers over
the years, with no one single cause supported by research. Instead,
bedwetting (primary nocturnal enuresis) is multifactorial
usually resulting from a number of factors at play that results
in a child wetting. (1,2) Understanding what medical
factors are at work will help you decide an appropriate approach
to treatment and credible resources to assist you.
Sleep or Arousal Disorder
Many children with bedwetting are described as deep sleepers,
or children who are not easily roused from sleep, by their parents.
Sleep studies to document a specific disturbance in sleep patterns
or sleep arousal have been controversial. Wetting appears to occur
at all stages of the sleep cycle. (19) Although the
specific mechanism requires additional research, it is generally
accepted that children are not easily roused from sleep and are
often disoriented when awakened. (20)
A small percentage of children are sensitive to foods that contribute
to nocturnal enuresis. A number of children benefit from eliminating
foods such as citrus, caffeine and others. (21,22)
High Urine Production -
In most people the release of a hormone at night called vasopressin
reduces the amount of urine produced. Some children with nocturnal
enuresis release less vasopressin at night (i.e. no decrease in
urine volume). (23) These children produce more urine
than their peers and are more prone to bedwetting especially
when other factors are present.
Low Functional Bladder Capacity
Another common factor in children with bedwetting is a
small functional bladder capacity. (24,25) These
children have less forewarning of the need to urinate and feel
more urgency. Some of these children may also exhibit daytime
symptoms. When a child's functional bladder capacity is low they
are less able to hold a normal amount of urine at night.
Irregular Bowel Movements
Some children with bedwetting are affected with bowel problems
such as irregular or infrequent bowel movements or constipation.
(26) When the rectum is full, the bladder's expansion
may be restricted or result in decreased sensitivity to bladder
Other causes of bedwetting, although uncommon, include
anatomic abnormalities, endocrine disorders and urinary tract infections.