Urinary tract infection

What is a urinary tract infection?

A urinary tract infection (UTI) is an infection of the bladder or the kidneys​​.

  • A bladder infection is called cystitis.
  • A kidney infection is called pyelonephritis.

Symptoms of a urinary tract infection may include:

  • fever
  • unexplained fussiness in a baby or young child
  • needing to urinate (pee) more often
  • pain or burning with urination
  • wetting during the day in a toilet-trained child
  • vomiting or abdominal (belly) pain
  • back pain
  • blood in the urine.

Causes of UTIs

UTIs occur when bacteria from the skin enter the bladder through the urethra (the tube that allows urine to leave the body from the bladder).

Urinary system
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The male and female urinary system are very similar, however the urethra in males is much longer than in females.

How UTIs are diagnosed

Your child’s doctor will diagnose a UTI through testing a sample of your child’s urine. Diagnosis involves three steps:

  • testing the sample of urine with a dipstick
  • studying the sample under a microscope
  • growing a culture (bacteria) in the sample in a laboratory.

Urine sample

In toilet-trained children, the urine sample should be taken mid-stream. In children who are not toilet-trained, the urine sample can be collected by a “clean catch”, a catheter (tube) or, sometimes, a urine bag.

Results of urine test

The doctor will consider the results of the dipstick test and the culture test. If the urine sample has been collected properly, a “positive” culture confirms a urinary tract infection. A “negative” culture confirms that there is no infection.

The final results of the urine culture test are usually ready in two or three days. The results will show which specific bacteria caused the infection and guide which antibiotics will treat them.

If a child’s urine has been collected in a urine bag and there is a positive result from a dipstick test, your child’s doctor should collect another urine sample by clean catch or a catheter and send it for further testing.

How to care for a child with a urinary tract infection


Depending on your child’s age, symptoms and medical history, they may require either oral antibiotics (antibiotics by mouth) or admission to hospital for intravenous antibiotics (antibiotics given into the vein).

Your child’s doctor will first prescribe a broad spectrum antibiotic (one that can treat most bacteria). Once the doctor knows the bacteria that have caused the urinary tract infection, they will prescribe a more specific antibiotic if necessary. Your child will only get better when they take the correct antibiotic for their infection.

Your child’s symptoms should improve within 48 hours of starting the correct antibiotic. Even so, continue to give the antibiotic to your child until it is finished. Finishing the antibiotic prevents the infection from returning and reduces the chance that your child will get an infection that is harder to treat with antibiotics in the future.

Pain and fever relief

Give your child acetaminophen or ibuprofen to help with any pain or fever. These medicines usually begin to work within an hour and do not interfere with antibiotics. You may need to give them during the first few days of treatment until the antibiotic starts to take effect.

Follow-up appointment

After your child starts antibiotics, make an appointment to see your child’s regular doctor. They can check how well the antibiotic is working and prescribe a different one if your child is still sick.

Other tests for children under two years

If your child has their first urinary tract infection with fever (known as a febrile UTI) before they turn two, they should have an ultrasound of their kidneys.

They may also need to have a test called a voiding cystourethrogram (VCUG) to look for urinary reflux, a condition that causes the urine to flow backwards from the bladder to the ureters and kidneys. Whether they have this test depends on the results of the ultrasound and on whether they are young and have had more than one febrile UTI (a UTI with a fever).

How to prevent a urinary tract infection

Most UTIs in young children are unavoidable. In an older child, you can help prevent a UTI by following the steps below.

  • Teach your daughter to wipe from front to back after peeing. This is important after a bowel movement, as it helps to prevent bacteria in the stool from entering the urinary tract.
  • Prevent your child from becoming constipated. Constipation​ means having bowel movements that are harder or less frequent than normal. It can sometimes prevent the bladder from emptying completely, leading to UTIs.
  • Encourage your child to drink plenty of liquids every day. Your child’s urine should be pale.
  • Encourage your child to pee every two or three hours and not hold the pee for long periods.
  • Some children with severe urinary reflux or other urinary tract abnormalities may need to take a low-dose antibiotic every day to prevent new infections.

When to see a doctor about a UTI

Call your child’s doctor during office hours if your child’s symptoms last more than 48 hours after starting an antibiotic.

Take your child to the nearest emergency department, or call 911, if your child:

  • starts acting very sick or seems lethargic (very sleepy)
  • complains of severe abdominal or back pain
  • is vomiting (throwing up) repeatedly and cannot keep down any fluids or medicines.

Key points

  • UTIs occur when bacteria enter the bladder through the urethra.
  • A urinary tract infection is diagnosed if there is a positive culture test.
  • Antibiotics will treat the infection.
  • If your child is aged under two years and has their first febrile UTI, they will need an ultrasound to look for kidney problems or severe urinary reflux.
  • If your child has had one febrile UTI, they should be assessed for a possible UTI during an unexplained fever.
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Shawna Silver, MD, FRCPC, FAAP, PEng​