Dear Doctors: Our son had some of the symptoms of appendicitis. His lower right side was aching, and he was throwing up. At the emergency room, it turned out that he was passing a kidney stone. He’s only 13 years old — isn’t that much too young? How does he stop from getting more?

Dear Reader: It’s true that the average age for developing a first kidney stone is typically in the mid-30s and ranges into the neighborhood of age 50 to 60. However, a growing number of physicians say they are now treating increasingly younger patients. This is occurring in our own practices, where we see more kidney stones in the 20 to 50 age population than we do in people who are 50-plus. And, yes, we are also seeing young adolescents, like your son, with this painful condition.

For those who are not familiar, a kidney stone is a bit of hard debris that forms from the solid wastes that are dissolved in the urine. These include salts, urea, minerals and other inorganic compounds. If the balance between solid waste to liquid in the urine falls too low, crystals can form. Over time, they bond together and develop into hard, stonelike objects. Kidney stones can be as small as a grain of sand and, while quite rare, may grow to as large as a golf ball.

Stones can sit in the kidney undisturbed and unnoticed for years. But if they move into the ureter, which is the tube that carries urine from the kidney to the bladder, problems can arise. Tiny stones can pass through the ureter undetected. Stones up to about 5 millimeters, which is roughly the diameter of an adult ureter, may also be able to pass through, but can cause significant pain. The ureter has no flex, and the rough exterior and irregular size of a kidney stone can slow its passage.

Stones can also become stuck. This blocks the flow of urine and forces it back into the kidney. The increasing pressure causes pain in the groin, back and belly. It can also lead to infection. Treatment can include medications to help pass the stone and to manage pain, antibiotics to treat infection and medical procedures to break up or remove larger stones. And, unfortunately, having had a kidney stone increases the risk of a repeat.

The reason why ever-younger patients are getting kidney stones is not yet clear. However, our modern diet, high in added salt, is a leading suspect. Data collected by the Centers for Disease Control and Prevention show that children and young adults now far exceed the recommended sodium intake of 2,300 milligrams per day. This skews the mineral balance in the urine, which, in turn, increases the risk of certain types of kidney stones. Not drinking enough water and being overweight also increase that risk.

Changing your son’s diet may help reduce the risk of developing more kidney stones. This includes limiting salty and ultra-processed foods, going easy on animal proteins, eating calcium-rich foods, staying hydrated and maintaining a healthy weight. And be sure to alert your family doctor to this incident, as they can offer guidance specifically tailored to your son.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu.