Daytime wetting and voiding dysfunction in children

To understand the different kinds of voiding dysfunction it is important to have an idea of how the bladder works. The bladder is like a balloon inside your body that fills up with urine. Imagine yourself holding a filled balloon. The fingers on one hand hold the neck of the balloon shut. These fingers are acting like a sphincter. The other hand rests on and around the balloon just like the bladder muscles (called the detrusor muscles).

To empty the balloon in the best way you relax the fingers holding the neck of the balloon shut and at the same time squeeze down with the other hand. To relax one hand and squeeze down with the other hand takes some coordination. This is just what the sphincter and bladder should do when you urinate-the sphincter relaxes at the same time the bladder muscle contracts.

When we are infants our bladders fill and empty without our control. During urination, our sphincter muscles relax. This type of urinating is done by a reflex in our spinal cord. As we get older, we start to learn to block this reflex through signals from our brain. Our brain learns that it can control when the bladder contracts and also stop it from contracting. This type of brain control of the bladder is how children should become potty trained.

The age at which children gain brain control over their bladder varies. Most, but not all, children in the United States have gained this control by 4 years of age. Children who have not developed brain control over their bladder may try to stay dry by contracting their sphincter muscles at the same time their bladder tries to empty. Sometimes a child either crosses the legs or squats down when trying to hold back urination. In most children, the reason they develop the pattern of contracting their sphincter muscles at the same time their bladder contracts is unknown. Unfortunately, once children begin this pattern, it is difficult for them to learn to relax these muscles when they try and urinate. This abnormal
activity of the sphincter muscles occurs in most children with voiding dysfunction

Constipation occurs frequently in children with voiding dysfunction. This may be because the same group of sphincter muscles for urination also help control the bowel movements. Constipation in children does not always act like constipation in adults. Children with constipation problems may only have infrequent bowel movements and some stool streaks on their underwear. Some children with constipation even have diarrhea. Most children should have a bowel movement every day.

There are three types of voiding dysfunction. These types include bladders that void at a smaller than normal amount of urine, bladders that void at more than normal amounts of urine, and bladders that contract against a closed sphincter. A child can have more than one type of voiding dysfunction such as a bladder that holds a small amount of urine and also contracts against a closed sphincter.

1. Small bladders: Some children's bladders hold less than a normal amount of urine. In these children their bladder feels full even with small amounts of urine, and may even contract without the child wanting it to. This type of situation can be visualized by replacing the balloon
   in our model of the bladder with a much smaller balloon. Some of these children try and delay urination by learning to contract down their sphincter muscles when the bladder feels full or contracts. Unfortunately, this can generate high pressures in the bladder which can damage the
   bladder or kidneys. It can also lead to urinating with a closed sphincter which is the third type of voiding dysfunction (discussed below)
2. Large bladders: Some children do not void frequently enough and their bladders hold a larger than normal amount of urine. Normally, as our bladder fills it sends signals to the brain and we become aware that we will soon need to go to the bathroom. By ignoring these signals over a long period of time some bladders become stretched out and floppy. Children with bladders like this may not notice that they need to go to the bathroom until the bladder is so stretched that it just can't hold any more urine. By then it may be too late for the child to get to the bathroom
   and they begin to leak urine. Often these children also learn to hold back their urination by tightening the sphincter muscles.
3. Voiding against a closed sphincter: Many things may cause a child to be unable to relax their sphincter muscles when trying to urinate. Once this pattern happens it can become a vicious cycle. Imagine squeezing down on a balloon while the fingers on the other hand squeeze the
   neck of the balloon shut-this generates a lot of tension and pressure in the balloon. When a child voids against a closed sphincter a lot of pressure is generated in the bladder. Over time, this pressure can cause the bladder muscles to become very thick and the bladder may generate frequent, strong contractions. These contractions may cause the child to need to urinate frequently, and urgently. They can also cause wetting. The high pressures in the bladder may force urine backwards (reflux) up the tubes (ureters) from the kidneys and damage the kidneys. Often the bladder does not empty completely which causes it to get to the full point more rapidly and creates frequent urination. Incomplete emptying of the bladder, ureteral reflux, and damp underwear can all increase the chance of developing urinary tract infections.
    

The health care provider will start the evaluation with some detailed questions about the child's voiding habits and bowel movements. An elimination diary that keeps track of how often the child voids, has a bowel movement and wets is useful. A physical examination will be performed. Some children with wetting problems or urinary tract infections have causes other than dysfunctional voiding. By asking questions and performing the physical examination the health care provider will be checking to see if any of these other causes are present. Other tests such as an ultrasound or X-ray may also be necessary to make sure that one of these causes is not present. The urine is checked to look for any signs of infection or kidney damage.

Having the child urinate into a special machine (called a Uroflow) can monitor how much and how fast he or she urinates. This is sometimes combined with monitoring the sphincter activity by two sticky patches placed near the child's bottom. These patches are connected to wires and measure the sphincter activity. An ultrasound probe gently placed on the skin surface above the bladder may be used to determine how much urine is left in the bladder after voiding.

Some children will require more invasive bladder tests. A voiding cystourethrogram, or VCUG, involves placing a catheter in the bladder. The bladder is filled with liquid contrast material that shows up on an X-ray. After the bladder is filled, the catheter is removed and the child is asked to void and more X-rays are taken. This test shows the shape of the bladder, how well it empties, and if any reflux up the ureters occurs.

A urodynamic test also requires placement of a catheter. In this test, a second small catheter is also placed in the child's rectum. These catheters can monitor the exact pressures in the child's bladder during both filling and voiding. At the same time the activity in the sphincter is observed. If the bladder is filled with contrast during a urodynamic test, X-rays can also be taken and the study is called a fluorourodynamic study.
 

The treatment for dysfunctional voiding depends on the type and cause of the dysfunctional voiding, as well as the patient's age and ability. A child should never be punished for wetting since this is something that is not under their control (it would be better to reward the child for voiding which is under their control). Constipation can often be improved by increasing the fiber and fluid in a child's diet. Treating
constipation may result in improved voiding.

For children with a small capacity bladder, an anticholinergic medication may increase the bladder capacity. This medication can also decrease bladder contractions in patients whose bladder contracts too frequently. It is important that these children go to the bathroom frequently. Trying to "hold on" can damage the bladder and kidneys and teach the child improper voiding.

For children with a large bladder, who do not void often, the best treatment is frequent trips to the bathroom (about every 2 hours). Since these bladders may be stretched out and not empty well, it is important for many of these children to sit down and spend several minutes trying to make sure the bladder is completely empty. By frequently and completely emptying the bladder the child reduces the chance of wetting or infections and starts to recognize the early signals from the bladder telling the brain that it's time to urinate.

Children who contract their bladder against a closed sphincter need to learn to relax their sphincter when voiding. Having the child void every 2 hours while sitting and relaxing for several minutes helps many children learn to void normally. By listening to the urine stream, both the parents and child may be able to detect good and poor flows. Increasing the amount of water they drink helps keep the urinary tract flushed out and may decrease constipation. Some children will require biofeedback methods to teach them to recognize how to control their sphincter muscles. Rarely, a child may require daily catheterizations or surgery to treat dysfunctional voiding and prevent kidney damage