Parents, and physicians, too, are increasingly concerned about the potential long-term effects on children of radiation from diagnostic procedures. We shouldn’t irrationally fear radiation from ordinary x-rays or CT scans, but we should use these tests judiciously — when the benefit of getting the information from them outweighs the still very small risk of doing them. Of course we should always have been doing things that way; the latest evidence reenforces what we’ve always known, but have not always acted upon. Some new recommendations about managing urinary tract infections (UTIs) in young children will allow us to reduce radiation exposure.
UTIs are not uncommon in children. They come in two forms. The less serious, and more common form, is an infection of only the bladder, called cystitis; the more serious, and less common form, is infection that involves the kidneys, called pyelonephritis. Both are generally caused by several bacteria that are normal inhabitants of the intestinal tract, particularly one called E. coli.
It has been known for many years that children with structural abnormalities of the urinary tract are especially susceptible to getting a UTI. These abnormalities can be misconnections of various parts of the urine drainage system, but the most common one is backward movement (reflux) of urine from the bladder upstream back to the kidneys. In spite of the association of these abnormalities with UTIs, the majority of children who get a UTI have a completely normal urinary tract.
For many years, certainly the 35 years I have practiced, children who had a UTI were checked to see if they had an abnormal urinary tract. The usual practice was to check boys after their first UTI, girls if they had a second one. One of the standard tests to do this was called a voiding cystourethrogram, or VCUG. This test is a radiological one, and it exposes children to radiation. How much radiation? Unlike many radiological procedures, the VCUG employs fluoroscopy, which means that the amount of radiation varies a bit from patient to patient because the amount of fluoroscopy time can vary with the operator. On average, though, the amount of radiation from a VCUG is anywhere from 10 to 20 times that of a simple chest x-ray. You can think of a VCUG as giving about the same amount of radiation as we get from background radiation from living about 6 months at sea level.
Radiologists have made a lot of progress in limiting the amount of radiation they need to do x-rays in children. But better than reducing radiation is not needing it at all, and that is what the American Academy of Pediatrics now recommends for evaluation of most children with a UTI. Some children will still need a VCUG, mainly those who have repeated UTIs, but for most children the most useful information can be obtained by ultrasound, which does not carry any radiation. You can read their recommendations here.
Why does the AAP no longer recommend a VCUG for most children? The answer is a good example of an important principle in medicine — balancing risk vs. benefit. The VCUG does give information, but it turns out that the information, although interesting, is not crucial in actually deciding to do for the child after their first infection. So the risk of the VCUG, although very, very tiny, brings no real benefit. So even that small risk is not worth taking.