Ask the Pediatrician: Dr. Molly

Category: Infections

Bladder infections in babies uncommon, but need follow up

Recently, I had a baby in the office who had been running a fever for almost three days. He didn't have any other symptoms: no runny nose, diarrhea, rash or big change in his sleeping patterns. He was teething and his parents had originally chalked up the fever to that (even though teething causing fever is a myth), but as the days passed they thought they had better be on the safe side and brought him in. As predicted by his history, he had a completely normal exam other than his fever. I told the parents it was likely a viral illness with fever as the only symptom and chances are his fever would break in the next day or two and he may develop a rash then.

Another day and half passed and the fever persisted. By now it was Saturday and the mom called to ask if the fever was still due to a virus. Five days of fever is my limit without further testing and I sent him off to the After Hours Clinic for assessment where he had some labs done. The baby's blood work was normal, but a urine test revealed blood and white cells indicating a probable urinary tract infection.

Boys and girls are susceptible to urinary tract infections (UTIs) at any age, although they are more common in girls, and the hallmark symptom in infants and toddlers is fever. Most of the babies will not appear to have pain and most will not have any other symptoms. Those who have other symptoms will often have vomiting or diarrhea and some will be cranky.

Because the only way to get a urine sample that can be relied on for "clean" results is to catheterize the infant, it isn't the first thing we choose to do when a baby has a fever. Indeed, on days one-three of fever far and away viral illness will be the cause unless the baby looks particularly ill. After the third day, the likelihood of a bacterial infection increases and it is at this point that searching for a bacterial cause in a child who doesn't appearing ill otherwise makes sense. In addition to a catheterization to obtain a clean urine sample, most doctors will do blood work including a complete blood count and a blood culture. If all of these tests are normal, chances are the child has a viral illness, but if the white blood cell count is elevated or the urine looks abnormal, a bacterial illness is more likely.

Rates of UTIs in the first two years of life vary. Up to 7 percent of girls with no obvious source of their fever will be found to have a UTI. For boys, the rate is lower and depends on whether he is circumsized. About 2 percent-3 percent of uncircumsized boys under the age of 2 with a fever of unknown origin will have a UTI and 0.2 percent of circumcised boys will be found to have a UTI when no other cause of the fever is found.

Treating a UTI involves antibiotics; whether those can be oral and given at home or need to be given via IV in a hospital depends on a lot of factors including how ill the child appears, how well hydrated he is and whether the parents are able to get the child to take the medication needed.

Diagnosing, treating and confirming resolution of the UTI is just the start though. About a third of infants and toddlers with UTIs will have underlying problems including structural problems of the kidneys, ureter or bladder and/or a condition called vesicoureteral reflux (VUR).

VUR happens like this: you go to pee and instead of all of the urine coming out the front through the urethra, some of it backwashes (refluxes) up toward the kidneys. This constant reflux can cause any little collection of bacteria in the bladder that crawled in from the outside and would normally just get peed out to have the chance to take hold higher up the chain in the kidney and cause infection. Because infection can cause scarring of the kidney and later high blood pressure as a result, preventing infection makes sense. Most children with VUR will outgrow it by about 5 years of age and a very small number of them will need surgery to correct it if the kidney is undergoing constant back pressure leading to kidney swelling.

Diagnosing VUR is not fun. Two tests exist to diagnosis it and each have pros and cons. Both involve putting a catheter into the bladder and injecting either dye or a nuclear substance. When the child pees, images of the dye or nuclear contrast are taken to find out where it goes. If it heads up toward the kidneys, the VUR is diagnosed. In addition to this test, called a VCUG, an ultrasound of the kidney should be done to ensure the anatomy is normal - there isn't an extra lobe to the kidney or it isn't malformed or malpositioned. Some kids will also need a DMSA, which is a nuclear study done using an IV to administer the contrast that tells how well each of the two kidneys is functioning. This is only needed if significant kidney damage is probable.

Although unpleasant, doing these follow-up tests in all toddlers and infants who have had a UTI is essential because such a large percent of them will be abnormal. Although there is some debate in the medical community, most doctors will put these children with abnormal studies on a once-a-day antibiotic to minimize or prevent subsequent kidney infections.