Voiding Dysfunction: Overview

What is voiding dysfunction?

Holding and releasing urine is a very complex process. Urination involves the coordination of two different systems: the bladder (involuntary control) and the sphincter (voluntary control).

The bladder muscle relaxes as it fills to allow storage of urine. When the bladder has reached 50% capacity, a signal is sent to evacuate the bladder. During the time of bladder filling, the sphincter muscle is in a state of contraction, holding the urine back. It is not until the sphincter is relaxed that the bladder contracts to empty.

During normal development, children become more aware of their bladders. This maturation process allows the ability to control their bladder and prevent wetting. Children learn to override the normal tendency of the sphincter to relax by contracting their sphincters, thus staying dry. This is a normal reaction of a child to prevent wetting and allows a child time to get to a bathroom. However, an unhealthy situation occurs when a child continues to maintain a contracted sphincter against a full or straining bladder (holds for long periods of time). This, in essence, sets up two muscles working against each other. Over time, the muscle will become to large, with the bladder wall reaching two to three times its normal thickness because of muscle fiber enlargement. In severe cases, damage to the kidneys can occur.

What causes voiding dysfunction?

The exact cause is unknown, but there is a behavioral component to the change in the bladder caused by excessive holding and increased bladder irritation.

Who gets voiding dysfunction?

Voiding dysfunction can occur in males and females, most commonly in the ages of 4 to 16.

Voiding dysfunction is often a learned behavior by children who hold their urine all day. Children begin the pattern or behavior for many reasons, including not wanting to stop what they are doing to use the restroom, voiding infrequently because of discomfort with voiding or a social environment that discourages them from using the bathroom. No matter what the reason, the outcome is the same, an inability to relax the sphincter muscle to allow urine to flow out without interruption and allow complete bladder emptying.

After the holding process has been learned, it is difficult to change. A child usually begins holding without symptoms. After a period of time, the bladder muscle becomes strong as it resists against the sphincter (control mechanism). The bladder will eventually overcome the tight sphincter muscle and will empty on its own at an undesirable time.