Mayo Clinic Study Finds Liver Transplantation Can Be Performed Safely for Obese Patients

Tuesday, June 19, 2007

A new Mayo Clinic study found that liver transplantation can be performed safely in patients who are considered medically obese. Mayo researchers will report their findings on June 22 at the International Liver Transplantation Society's Annual International Congress in Rio de Janeiro, Brazil.

"Two-thirds of Americans are overweight or obese, and obesity-related liver disease is rapidly becoming the most common reason for liver transplantation," says Michael Charlton, M.D., medical director of the liver transplant program at Mayo Clinic in Rochester, and lead author of this study. "Because the majority of liver transplant candidates are overweight or obese, it has become vital to determine how this may affect the success of transplantation."

A previous national study conducted with data from the United Network for Organ Sharing (UNOS) found that liver transplant patients who were obese had poor outcomes following transplantation. Obesity was calculated using Body Mass Index (BMI), a formula that uses height and weight to estimate body fat and associated health risks. Medical providers consider a BMI of 25-29 as overweight, 30-34 as Class I obesity, 35-40 as Class II obesity and a BMI over 40 as Class III obesity. Based on this study, many transplant centers in the United States currently will not perform liver transplants in patients with Class III obesity.

However, according to Dr. Charlton, the previous study may have been flawed because of how BMI was calculated. A common side effect of liver disease is ascites, the accumulation of fluid in the abdomen. The fluid weight from ascites is not routinely subtracted from the weight calculation for BMI; thus many liver transplant patients in the previous study may have been inaccurately categorized as obese, he says.

Dr. Charlton and his team set out to determine whether obesity, based on a revised BMI calculation after correcting for ascites, should prevent patients from receiving a liver transplant. They evaluated data from nearly 700 liver transplant recipients at Mayo Clinic in Rochester, the University of Nebraska Medical Center and the University of California, San Francisco, between 1990 and 1994. Pre-transplant BMI was recalculated to correct for the amount of ascites removed at the beginning of the patient's liver transplant. Researchers then categorized the patients based on their adjusted obesity class and evaluated survival at 30 days and annually to 10 years. The findings showed that outcomes for patients who were overweight or obese (classes I, II and III ) were at least as good as for patients who were not considered overweight.

"This study, and our experience at Mayo Clinic, demonstrates the importance of considering each candidate for liver transplant individually and not automatically excluding patients based on BMI," says Dr. Charlton. "Of course, weight reduction for obese patients will always provide health benefits, but weight alone should not be a barrier to liver transplantation."

More than 400 patients receive liver transplants at Mayo Clinic's sites in Minnesota, Florida and Arizona each year. Mayo Clinic is the most experienced liver transplant center in the nation, with some of the highest survival rates in the world.

Other Mayo Clinic researchers involved in this study include Jennifer Leonard, M.D., Julie Heimbach, M.D. and Michael Malinchoc.

For more information on liver transplantation at Mayo Clinic, please visit www.mayoclinic.org.

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