Diagnosing Urinary Tract Infections in Children

Urinary tract infections, or UTIs, occur when bacteria, and sometimes viruses and fungi, invade the urinary tract, through which the body removes wastes and excess water. The kidneys—two small organs that filter fluid and waste from blood to make urine—are located at the top of the urinary tract. Urine flows from the kidneys in one direction through two tubes called ureters and empties into the bladder before it leaves the body through the urethra.

Although infections can occur anywhere along the urinary tract, many begin when bacteria, usually Escherichia coli, or E. coli, in the anus are spread to the urethra and bladder in the lower part of the urinary tract.

UTIs are very common in children, accounting for up to one million pediatrician visits each year.

Risk Factors

Girls have an increased risk of developing UTIs because the urethra is located closer to the anus than in boys, making it easier for bacteria to reach the urethra. Urinating helps to flush out any bacteria in the urethra. By contrast, waiting too long to urinate can lead to infections. UTIs are also common in children who do not drink enough fluids, which reduces urine production and can cause constipation. Blockages in the rectum due to constipation can prevent the bladder from emptying; as a result, bacteria may grow in the urine that is trapped in the bladder or urethra.

Repeated UTIs often occur in children with voiding dysfunction, or unusual urination patterns that are caused by poor coordination between muscles in the bladder and urethra. Voiding dysfunction can prevent the bladder from emptying completely, increasing the risk of a urinary tract infection.

Children who have problematic bathroom habits, such as holding in urine for long periods of time, can develop voiding dysfunction. It can also occur in children with neuromuscular conditions, such as cerebral palsy or spinal cord injury, which disrupt the nerve signals that enable the pelvic muscles to relax.

Children who are born with a congenital kidney or urinary tract problem are at risk of developing more serious infections in the upper part of the urinary tract. Two congenital problems that may lead to kidney infections are vesicoureteral reflux, in which urine flows backward from the bladder into the ureters and kidneys, and hydronephrosis, in which a blockage between the kidneys and the ureters causes a buildup of urine in the kidneys.

Most UTIs are not serious. However, repeated kidney infections and the inflammation they cause can result in permanent scarring. This scarring can lead to chronic kidney disease, in which the kidneys don’t function properly and waste products can build up in the bloodstream. Children with chronic kidney disease due to frequent UTIs may develop hypertension, an increase in blood pressure that can occur when the kidneys cannot remove waste and fluids effectively.

Symptoms

Symptoms of UTIs depend on your child’s age. Infants and preschoolers may become irritable and have difficulty eating. Some may develop a fever but show no other sign of infection.

Older children may have the urge to urinate more frequently and experience pain or burning during urination. They may also notice that the urine smells foul or appears cloudy. Children with a more severe infection in the kidneys may develop a fever and chills or pain in the back.

Pediatricians at Hassenfeld Children’s Hospital at NYU Langone perform a physical exam and laboratory tests to diagnose a urinary tract infection.

Physical Exam

During a physical exam, the doctor asks you or your child about any symptoms he or she may be experiencing, such as: pain or burning during urination, a frequent and urgent need to urinate, a decreased appetite, or a fever. He or she may touch your child’s back to determine if the kidneys are tender or swollen. The doctor may also want to know if your child has had previous UTIs or has been diagnosed with any other medical conditions, particularly congenital kidney or urinary tract conditions.

Urine Tests

The doctor may request a urine sample to determine if there is evidence of an infection. You are given a sterile cup that can be used to collect a clean sample of your child’s urine. For babies, the doctor may obtain a sample using a sterile catheter that is quickly inserted through the urethra directly into the bladder.

The urine can be tested in the doctor’s office, or in an emergency room if your child is very sick and has a high fever. A special stick inserted into the collected urine determines if it contains leukocytes, a type of white blood cell that fights bacterial infections, and nitrites, which are found in urine if bacteria are present. The stick test provides immediate results.

If your child has a urinary tract infection, the urine sample may be sent to a laboratory that can identify the cause of the infection. Laboratory test results are usually available in two days.

Kidney Ultrasound

Doctors may also recommend a kidney ultrasound to look for an underlying kidney or urinary tract problem that may predispose your child to developing a UTI. During an ultrasound, a technician or radiologist places a device called a transducer on your child’s abdomen. The transducer emits high-frequency sound waves that produce a precise image of the kidneys and ureters on a monitor.

An ultrasound is used to evaluate the size and shape of the kidneys and other urinary structures. It can identify swelling in the kidneys or ureters and determine if there is debris in the bladder.

Voiding Cystourethrogram

A voiding cystourethrogram is an imaging test that may be performed if the doctor strongly suspects your child has vesicoureteral reflux, a common cause of recurrent UTIs. The radiologist inserts a small, flexible tube called a Foley catheter into the urethra and injects a contrast dye into the bladder. Specialists then take X-rays—in which high-energy beams of light create images of organs and other structures—when your child’s bladder is full and after it has been emptied.

The test is usually completed within 30 minutes. Babies older than two months may need mild sedation to reduce discomfort during the test.

Nuclear Scan

A nuclear scan, also known as radionuclide cystogram or a MAG3 scan, is another type of imaging test that is used to examine the flow of urine through the urinary tract system, through which the body removes wastes and excess water. This scan can determine if there are structural problems or scarring in the kidneys.

In this test, a radiologist injects a radioactive tracing material into your child’s vein. The tracing material is absorbed by the kidneys, and a special scanner that can detect the tracer takes pictures of the kidneys, ureters, and bladder before and after urination. An anesthesiologist may give your child a mild sedative before this test is performed to reduce discomfort.

If these tests reveal that your child has a congenital kidney or urinary tract problem, our doctors may refer you to additional specialists at Hassenfeld Children's Hospital who may recommend treatment with surgery or minimally invasive procedures.