Urinary Tract Infection
Diagnosis

Urinalysis and Culture

When you bring your child in for a urinary tract infection, we'll first discuss your child's general health and symptoms. Then we'll perform a urinalysis, which involves looking at your child's urine with a microscope. To be certain that there's an infection, we'll also do a urine culture to see if bacteria from the urine will grow in a culture medium. Your doctor will have the results of the urine culture after 24 hours. If there's an infection, an additional 24 hours is usually needed to find out which antibiotic will kill all of the bacteria.

The method of urine collection will affect the accuracy of the urine culture. It's important to:

• Wash the skin around the urethra with a cleaning pad to remove bacteria on the skin surface.
• If you collect the urine sample at home, place the sample in the refrigerator and then pack it in ice while traveling to the doctor's office.

To collect urine from infants and toddlers, a special bag is placed over the genital area. Because bacteria from the skin may contaminate these samples, it's sometimes necessary to insert a small plastic tube called a catheter through the urethra and into the bladder to get a clean specimen.

Other Tests

Children with confirmed urinary tract infections should be evaluated for abnormalities of the urinary tract. Twenty-five to 50 percent of children with a urinary tract infection have these abnormalities, and waiting until a child has two or more infections before doing the evaluation increases the risk of permanent kidney damage or scarring. This is especially important for infants and toddlers, since most of them will develop another urinary tract infection later.

We also test for vesicoureteral reflux, the abnormal backflow of urine from the bladder into the ureter and up to the kidney. Reflux is dangerous because it allows bacteria that might be in the bladder to reach the kidney. This can cause a kidney infection and lead to kidney damage.

Here are some of the basic tests we may suggest if your child has a confirmed urinary tract infection:

• Voiding Cystourethrogram (VCUG) — This test gives us important information about the shape and size of the bladder, the bladder neck or opening and the tubes, called ureters, that drain the urine from the kidneys into the bladder.
  
  During the test, a small, plastic tube called a catheter is inserted into your child's urethra and passed into the bladder. Then the bladder is filled with a fluid that will show up on the X-ray, called contrast media. While your child's bladder is filling, he or she can watch a video; we encourage children to bring their favorite one, but we always have a few on hand.
  
  Pictures are taken while your child's bladder is filling. When your child's bladder is full, we remove the catheter and take a picture as he or she urinates. After the study is done, we'll review the films with you and your child and discuss a plan of care.
  

  This procedure isn't painful, but it can be uncomfortable when the catheter is inserted into the urethra, and the experience may seem scary — or at least unusual — to children. We ask that at least one parent stay with your child in the room at all times. We will explain everything as we go. The test usually takes 20 to 30 minutes.

• Kidney and Bladder Ultrasound — This test is performed to get an outline of the kidneys, ureters and bladder. It looks for additional urinary tract defects that could be the cause of infection. Ultrasound doesn't involve radiation and is painless.
• Kidney (Renal) Scan — We may recommend this test if the above tests are abnormal. It can better demonstrate the actual function and drainage of the kidneys. A kidney scan can also show if there's kidney damage and scarring.

Reviewed by health care specialists at UCSF Children's Hospital.
Last updated March 10, 2010

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