(See also Overview of Urinary Tract Birth Defects.)
There are several different birth defects that affect the bladder (the expandable, muscular sac that holds urine). Some are apparent at the doctor's examination. Others require tests to evaluate the urinary tract.
Birth defects that affect the nerves to the bladder, particularly spinal cord defects such as spina bifida, cause problems in several ways:
Flaccid bladder: The nerve problem makes the bladder muscles limp and weak (flaccid). The bladder cannot contract properly to empty itself, so urine tends to fill up the bladder at low pressure.
Spastic bladder: The nerve problems cause the bladder to contract too much (spastic), and urine in the bladder is at high pressure. The bladder is small.
In some children, the bladder is sometimes flaccid and at other times spastic.
If children cannot empty their bladder completely, urine can become stagnant, which increases the risk of urinary tract infections (UTIs) or formation of kidney stones. Also, the full bladder may overflow, resulting in involuntary release of urine (called urinary incontinence). If the child's bladder cannot empty completely, the bladder is drained by inserting a thin, flexible, sterile tube (catheter) through the urethral opening into the bladder. This process is called catheterization. Catheterization is repeated several times each day because it is better to remove the catheter as soon as the urine has finished draining. However, sometimes the catheter must be left in all the time. If catheterization does not work, a surgical procedure called a vesicostomy may be done. In this procedure, doctors make an opening between the abdominal wall and the bladder. Urine drains from the bladder through the opening into a diaper.
If the urine is under high pressure, the urine may flow backward from the bladder into the kidneys (urinary reflux). Urinary reflux may cause recurring urinary tract infections, kidney damage, or both. Children who have a small bladder and increased bladder pressure may be given drugs to relax the bladder muscles or may be catheterized. If these measures do not work, doctors may do surgery to help decrease the involuntary release of urine and decrease bladder pressure so the kidneys do not become damaged. Some surgical procedures increase the size of the bladder. However, after surgery, children usually still need catheterization.
When the bladder is first developing in the fetus, it normally closes to form a muscular sac. Sometimes, the bladder does not completely close and it opens out onto the surface of the abdomen (called bladder exstrophy), allowing urine to drip through the abdominal wall rather than out the urethra. Children who have bladder exstrophy may also have an abnormally formed urethra and external genital organs (penis, testes, or clitoris) and sometimes abnormalities of the anus.
A similar disorder involves the connection between the bladder and the bellybutton (umbilicus) that is present when the fetus is first developing. This connection is called the urachus. Normally this connection closes before birth. If this connection remains open (called a patent urachus), urine drains out of the bellybutton.
In both disorders, infants are at risk of urinary tract infections. Doctors do surgery to close the abnormal openings and repair the bladder if needed.