Urinary Tract Infections in Infants

In very young babies, urinary tract infections are generally caused by bacteria germs that reach the urinary tract via the bloodstream.
What might be the cause of a urinary tract infection in a four-month-old girl? She was very sick with a fever of 105. They first thought it might be spinal meningitis and did a spinal tap. That came out OK. Ultrasound picked up the urinary infection.
In very young babies, the bacteria germs generally reach the urinary tract by the bloodstream. Older infants and children tend to get infections from bacteria reaching the bladder through the opening where urine comes out (urethra). Once the bacteria reach the bladder, they can cause varying degrees of inflammation and severity of disease. Although an infection begins in the bladder, the germs can then reach the kidneys by moving up (refluxing) toward them. Factors, such as the shape, form, and function of the urinary tract, also play a role in who is more likely to get an infection.

Making the diagnosis of a urinary tract infection (UTI) in young infants is not always easy. Infants do not express themselves in the same ways older children and adults do. They usually have non-specific symptoms, including unexplained fever (just like your four-month-old did), vomiting, irritability, and lethargy.

Collecting specimens of urine to study in the lab (urine culture) is at best difficult, since bag-collected specimens in girls do not give very reliable results. It is often necessary to use some invasive method like putting a small tube into the bladder through the urethra or directing a needle into the bladder from the outside and aspirating urine in this way.

Infections of the bladder and sometimes the kidneys are common in children. The prevalence of UTI in infants between two months and two years is as high as five percent and more common in girls. Having a high index of suspicion for a UTI in infants is important since this young age group is at highest risk for kidney damage from such an infection. Once the diagnosis is accurately made, the correct antibiotic can be used to treat the germ causing the infection and your infant can be properly evaluated and followed closely for recurrences.

Henry Bernstein, M.D., is currently the associate chief of the Division of General Pediatrics and director of Primary Care at Children's Hospital, Boston. He also has an academic appointment at Harvard Medical School.

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