The normal urinary tract has two kidneys, two ureters, a bladder, the sphincter muscle and a urethra.
The kidneys filter the blood and make urine. Urine goes from the kidneys to the bladder through tubes called ureters. Where the ureters and the bladder join, there is a valve-like mechanism. This mechanism prevents the urine from backing up to the kidneys. As the bladder fills with urine, it sends a message to the brain. The brain then sends a message to the sphincter muscle to relax, while the bladder muscle squeezes, allowing the bladder to empty. This is called voiding or urination.
A urinary tract infection (UTI) is an inflammation of the bladder or kidneys. Normally urine is sterile and does not contain bacteria (germs). Bacteria may enter the body through the urethra and cause a UTI. Infection in the bladder is called cystitis (cis-ti-tis). An infection of the kidneys is called pyelonephritis (Pie-lo-ne-fri-tis).
The symptoms vary with the child's age. An infant or toddler may have a fever, be fussy, vomit, have diarrhea, or eat poorly.
For an older child, it may hurt or burn to urinate and there may be pain in the abdomen, side, or back. There may be a fever. A child who is usually dry may begin to wet and need to go to the bathroom very often. The urine often smells bad.
If these symptoms occur, it is important to collect a urine sample from the child to see if there is are signs of infection. A urinalysis may provide early clues that an infection may be present. A urine culture that shows growth of bacteria confirms the infection. The culture takes at least 48 hours to complete. In infants and young children, a catheterized urine specimen may need to be obtained.
How common are urinary tract infections?
Urinary tract infections are common in infants and young children. Urinary tract infections are three times more common in infant males than females. Uncircumcised male infants have ten times greater chance of developing a UTI during the first six months of life than circumcised males. After six months, infections are more common in females. The greatest numbers of UTIs occur in children two to six years of age. Approximately 6% of girls in this age will develop a urinary tract infection.
How often is there a physical problem associated with a UTI?
In about half of all children, there is a physical reason for a UTI or a reason why the recurrent urinary infections put the kidneys at greater risk of injury. The younger the child is at the time of the first infection, the greater the chance there is a physical problem. Thirty to 50 percent of children with a UTI have a condition known as reflux. Reflux means that the urine flows backwards into the kidneys. This allows the bacteria to travel from the bladder to the kidneys, and potentially damage the kidneys.
Who should be evaluated?
Any child who has had one urinary tract infection proven by urinalysis and urine culture with associated fever or who is less than 2 years of age, should have X-ray studies done. These include a renal ultrasound and a voiding cystourethrogram (VCUG). Children who are older and potty-trained and who did not have a fever with the infection may not necessarily need evaluation after the first infection. Evaluation should be considered in children who have recurrent urinary tract infections. In these children, evaluation of voiding pattern with a uroflow study and constipation status by an abdominal xray are also important.
- For a renal ultrasound, warm jelly is placed on the abdomen and back and a probe is moved over the surface of the skin. This produces a special kind of picture of the kidney and bladder. This picture shows the size of the kidneys and the bladder, and if there are any other problems such as previous scarring or swelling of the kidneys (hydronephrosis), or thickening of the bladder wall.
- A voiding cystourethrogram is a test where a small tube called a catheter is inserted in the bladder. The bladder is filled with a dye and x-rays are taken. Once the bladder is full, the child is asked to urinate and x-rays are taken again. If the fluid with the dye is seen backing up the ureters to the kidneys, reflux is present.
- A uroflow study is a non-invasive test in which the child is asked to arrive with a full bladder and urinate in a special container which is connected to a computer. Sometimes sticky patches with wires attacted are also placed on the patient to look at sphincter muscle activity during urination. After the child empties his/her bladder, an ultrasound device is used to check to make sure the bladder is empty (post-void residual or PVR).
Why do children without physical abnormalities develop UTIs?
There are several factors that may make a child more likely to get a UTI.
- Genetics can play a role. Children with UTIs often have other family members with a history of UTIs.
- Some children's bladders are less able to fight off bacteria.
- Children who do not empty their bladders often enough or who do not empty their bladders completely are more likely to get infections. The longer urine is held in the bladder, the more time there is for bacteria to grow.
- Poor wiping habits. This means not wiping front to back in girls.
- Constipation increases the amount of bacteria in the area of the urethra, and also may prevent the bladder from emptying completely.
How do I take care of UTIs?
Antibiotic treatment is necessary for all infections. Untreated urinary tract infections can lead to serious kidney damage. The younger the child, the greater the risk of damage.
What can I do to prevent infections?
You should have the child:
- Go to the bathroom often and take the time to empty the bladder
- Use good hygiene. Girls should wipe from front to back.
- Have daily, soft bowel movements. If constipation is present, it needs to be treated.
- Drink lots of fluids
- Avoid bubble baths or harsh soaps that could be irritating to the skin
What can I do if my child has repeated infections?
In addition to the above, your doctor may prescribe a daily low dose of antibiotics for 3 to 6 months, or probiotic therapy. Your child will also be evaluated to see if there are anatomic abnormalities or elimination problems that need to be treated.
Page reviewed on: Apr 29, 2009
Page reviewed by: Leslie T. McQuiston, MD