Q. Can children get kidney stones?

A. Believe it or not, children can get kidney stones. In the past, this problem was seen mostly in middle-aged adults, but it is now being diagnosed in children as young as 5 or 6. Pediatric kidney specialists are seeing a steep rise in young patients with kidney stones.

A kidney stone is made from mineral salts in the urine. If the concentration of a particular mineral in the urine is too high, crystals form. The crystals can gradually increase in size, forming a kidney stone.

Most kidney stones are tiny, about the size of a grain of sand. These small stones are usually passed out of the body, through the urine without intervention. Larger stones cause problems because they can block the drainage of the kidney, resulting in obstruction and extreme pain. Sometimes these stones can be blasted with high-energy sound waves that break them up into smaller pieces. In severe cases, they need to be surgically removed.

Too many salty foods coupled with too little water seems to be fueling the rise in childhood kidney stones. This combination reduces the amount of urine. This increases the concentration of stone-forming substances in the urine.

Children tend to drink too little water. In addition, some children do not want to go to the bathroom at school. Others don't have time or may not even feel thirsty.

Children with kidney stones can experience severe pain in their side, back or stomach. There may be blood in the urine. Sometimes there are no symptoms; the stone is accidentally discovered on an X-ray when the child is being treated for something else.

What can parents do? Make sure your children are getting enough to drink. Water helps dilute the urine so mineral salts cannot crystallize, but are instead removed from the body. If your child's urine is a dark yellow color, he or she may not be getting enough fluid.

Substitute fresh foods for processed foods in your child's meals and snacks whenever possible. Salt lurks in fast foods, canned meats, shoyu, saimin and chips.

Heredity may also play a role, so if an adult in your family ever had kidney stones, it is even more important to instill lifelong habits of good hydration and limiting salty foods in your children.