By Philip E. Gleason, MD
Toilet training can be one of life's greatest accomplishments, and greatest frustrations.
Toilet training usually occurs as a natural developmental process during the first 3-4 years of life. In many respects, this represents a natural maturation of the bladder. At birth, voiding is an automatic reflex. When the child makes urine and the bladder fills up, the body will sense the full bladder and the bladder will squeeze and empty as an automatic reflex, more or less on auto-pilot. As such, parents will be changing diapers 8-10 times a day. As the child grows and develops, the automatic reflex of the bladder will begin to relax and you can begin to take control of the bladder. As the bladder fills up, the child can sense and feel the bladder. You can feel that the bladder is getting full and that you will need to go to the bathroom, but if you are driving you can wait to get home. If the bladder is very full, you may need to stop at a gas station or rest stop, but can nevertheless control the bladder. The child then voids and the cycle will start all over again.
While this sounds simple, it does appear to represent a fairly complex maturation process. In many respects, the bladder is being asked to do two opposite things. On the one hand the bladder is being asked to relax and store urine for several hours without leaking. Then the bladder is being asked to void and empty completely to allow the cycle to start over. This may in fact account for the fact that toilet training occurs after children learn to speak and walk and reach some other fairly complex developmental goals.
To accomplish toilet training, the bladder size, or capacity, needs to be adequate to hold 3-4 hours worth of urine. In addition, the brain and central nervous system begin to take control and relax the bladder to hold urine. Last, at night, a hormone known as anti-diuretic hormone (ADH) helps cut down how much urine is made through the night, to help sleep through the night without having to get up.
Once the bladder is full, the bladder muscle contracts to squeeze and empty the bladder. In addition, the sphincter muscles which also help hold urine relax and allow the bladder to empty completely. The sphincter muscles then regain their muscle tone to close the bladder and the cycle starts all over again.
The bladder can be visualized on the graph in the lecture slides. When the bladder is empty, the bladder pressure is low. Even as the bladder begins to fill with urine, the bladder relaxes and stretches and expands and the bladder pressure still stays fairly low until the bladder is fairly full. Then, the bladder pressure begins to rise and you begin to feel the bladder and tell that you need to empty the bladder. When the bladder squeezes and empties the bladder volume empties and the pressure returns to a low level and the cycle starts over again.
As mentioned, at night there is also anti-diuretic hormone produced that helps concentrate and cut down how much urine is made through the night. ADH is produced by the brain at night but is not produced during the day. With ADH you will make less urine per hour through the night than you do during the day. In some respects this is because you are not drinking or eating through the night. However, even if you were, with ADH you would still make less urine per hour at night than during the day. This may, in part, be what allows us to sleep 8-10 hours at night without needing to get up to pee or void, when during the day we may be going to the bathroom every 3-4 hours.
As such, the body goes through a fairly specific sequence of toilet training. First, you get control of the bowels at night. Second, you get control of the bowels during the day. Third, you get control of the bladder during the day. Fourth, and last, you get control of the bladder at night.
The next lecture topics will talk specifically about night-time control and bedwetting, called nocturnal enuresis. Then we will talk about daytime control and incontinence, sometimes involving dysfunctional voiding and called diurnal enuresis.
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