You may wonder why a diagnosis of high or elevated blood pressure in children is so important. Although children don’t usually suffer the consequences of high blood pressure in the pediatric years, Dr. Kaelber said that, unless properly treated, it can result in early heart attacks, strokes and kidney disease.

Elevated blood pressure in children predicts high blood pressure in adults, a leading risk factor for heart attacks and strokes. Already in young adults who’ve had elevated blood pressure as children, “you can see two kinds of cardiovascular damage,” Dr. Joseph T. Flynn, lead author of the new guidelines, said in an interview. “There is thickening of the left ventricle, the heart’s main pumping chamber, and thickening of blood vessel walls that is clearly tied to atherosclerosis and heart attacks in adults.”

Because high blood pressure often runs in families, detecting it in a child may prompt a check of the parents and other family members and end up saving their health and lives, Dr. Flynn said.

And as demonstrated by Matthew Goodwin’s experience, in about 20 percent of cases there is an underlying and correctable cause for high blood pressure in children. Failing to make the correct diagnosis can be disastrous. As Mrs. Goodwin put it bluntly, “Matthew could have died.”

The prevalence of elevated blood pressure and frank hypertension in children and adolescents has risen dramatically in recent decades, largely the result of increasing overweight and obesity in the young. An estimated 17 percent of children aged 2 to 19 are obese, and approximately two million children have hypertension.

Other contributors to the prevalence of hypertension in children include a growing dependence on fast foods, processed foods and snacks that are high in salt, causing excess sodium and fluid in the blood and an added strain on the delicate blood vessels that feed the kidneys.

The new guidelines from the pediatric academy urge health care practitioners to measure and record blood pressure at every well-child or preventive care visit, whether or not the child is overweight or there appears to be anything wrong. If the blood pressure reading is recorded in an electronic health record, the computer does the necessary calculation to determine if the reading is normal.