In a new and disturbing twist on the obesity epidemic, some overweight teenagers have severe liver damage caused by too much body fat, and a handful have needed liver transplants.

Many more may need a new liver by their 30s or 40s, say experts, warning that pediatricians need to be more vigilant. The condition, which can lead to cirrhosis and liver failure or liver cancer, is being seen in kids in the United States, Europe, Australia and even some developing countries, according to a surge of recent medical studies and doctors interviewed by the Associated Press.

The American Liver Foundation and other experts estimate that 2 to 5 percent of American children over age 5, nearly all of them obese or overweight, have the condition, called nonalcoholic fatty liver disease.

"It's clearly the most common cause of liver disease," said Dr. Ronald Sokol, head of public policy at the liver foundation and a liver specialist at Children's Hospital and University of Colorado, Denver.

Some experts think as many as 10 percent of all children and half of those who are obese may suffer from it, but note that few are given the simple blood test that can signal its presence. A biopsy is the only sure way to diagnose this disease.

The disease is most common in overweight children with belly fat and certain warning signs, such as diabetes or cholesterol or heart problems.

However, it has been seen in a few children of normal weight.

If cirrhosis has not yet developed, fatty liver disease can be reversed through weight loss.

AFTER COLON SURGERY, NOT ENOUGH FOLLOW-UP

Many colon cancer patients aren't getting the screenings recommended after surgery to make sure the disease hasn't returned, new research shows.

Only about 40 percent of the 4,426 older patients in a study of federal records got all the doctor visits, blood tests and the colonoscopy advised in the three years after cancer surgery, according to the results released today in the journal Cancer.

While nearly all made the doctor visits and almost three-quarters got a colonoscopy, many didn't get the blood tests that can signal a return of colon cancer, according to the researchers at University Hospitals Case Medical Center in Cleveland. Dr. Gregory Cooper, a gastroenterologist who led the study, said health providers are probably most to blame.

ASSOCIATED PRESS