When asked what his pain felt like, a Tucson, Ariz., teen pictured a red-hot, molten rock in his stomach.

To deal with it, he envisioned rain hitting his rock, cooling it. The rain got heavier and heavier, erupting into a full-blown monsoon.

Cooling from red-hot to gray, the rock finally shattered, and the rains washed the ash away.

The pain was gone.

This technique — known as guided imagery — has proven dramatically effective in controlling the chronic abdominal pain suffered by as many as 20 percent of schoolchildren, according to a University of Arizona study.

“I frankly was shocked at how much and how fast the kids have improved,” said Dr. Thomas Ball, a professor of clinical pediatrics, who led the study.

“I have been a pediatrician for 20 years and have struggled the whole time with these kids in my practice. I’ve banged my head against the wall trying to help them. Finally, here is something that works.”

Surveys show that from 10 percent to 20 percent of children report pain attacks — severe enough to interrupt their lives — occurring at least three times during a period of three months. Most experience the pain weekly and often over years of time, resulting in missed school and frequent doctor visits.

Sometimes, physicians can find the cause, such as a gastric ulcer, inflammatory bowel disease, tumors or kidney problems.

But in most cases — 90 percent to 95 percent — no cause is found, and nothing has worked. Drugs to coat the gastrointestinal tract or to stop spasms have failed, Ball said.

Turning to alternative therapies, researchers decided to try a technique combining relaxation, visualization and light hypnosis known as guided image therapy. It has been used effectively to help children battle cancer pain.

In the first attempt to use it against chronic childhood abdominal pain, children ages 5 to 18 were trained in relaxation and imagery in four weekly sessions, each 30 to 50 minutes long.

The children were asked to create their own mental image of what the pain looked like, then something that would end it.

They were asked to practice the technique twice a day for a month and to keep diaries of their pain episodes.

At the end of the first month or training, the number of days of abdominal pain decreased by 36 percent. By the end of the second month, that effect nearly doubled, to a 67 percent drop in days of pain.