The medical term used to describe wetting the bed is nocturnal enuresis. Enuresis comes from the Greek word enourein, meaning to urinate. Non-nocturnal enuresis is also a common condition in children, in which they cannot control urination during the day.
Nonetheless wetting the bed is the most common urological complaint among children. It is also one of the most common issues faced by pediatricians. It affects about 2% of all children over the age of six.
In the past, wetting the bed was most commonly thought of as psychological problem, or insufficiency. We now know, however, that it is most commonly simply a developmental problem related to deep sleeping. Because it is a developmental problem, it will usually sort itself out in time.
The fact it will sort itself out in time, however, is of little consolation to the children this condition affects. For any child that suffers from this condition the psychological effects are quite real.
The Bladder and the Brain Communicate
The bladder is the body's receptacle for urine. Like any container, it can be anywhere from empty to full. Usually the bladder can send a signal to the brain to let it know when it is either empty or full. When it's full of the bladder sends a message to the brain that it's time to pee. You can then respond to that message by going to the washroom.
A problem arises in children for whom this signalling from the bladder to the brain is underdeveloped. The weak signal from the bladder, in combination with the brain being in a very deep sleep, results in bedwetting.
How nocturnal enuresis usually manifests itself is as follows: the child sleeps so deeply that the brain does not pick up the signal from the bladder that it's full, and the result is a wet bed. It is possible that this effect is sometimes exacerbated by a weak urethral sphincter.
The Urethral sphincter
Urination is physically brought about by two things: muscles within the bladder walls contract to push urine out, and the urethral sphincter relaxes to let the urine out. Weakening of these properties could aggravate enuresis.
"until what age will my child have this condition?"
So, if bed wetting is purely a developmental issue, when do children usually outgrow it? Complete dryness is usually achieved for girls by the age of six, and boys by the age of seven. The sort of frequent bed wetting which we would call nocturnal enuresis however is more uncommon. Of course, each case is different, and in rare cases nocturnal enuresis can last until the late teens.
What we can look at, however, are percentages. At the age of 4 1/2, 30% of children still wet the bed but only 8 of that 30% still wet the bed more than two times a week. That 8% of children wetting the bed on a frequent basis goes down to 2.6 % by the age of 7 1/2.