[1] Mayo Clin, Coll Med, Div Gastroenterol & Hepatol, Rochester, MN 55905 USA
[2] Mayo Clin, Coll Med, Dept Pathol, Rochester, MN USA
[3] Mayo Clin, Coll Med, Dept Radiobiol, Rochester, MN USA
[4] Mayo Clin, Coll Med, Div Gastroenterol & Gen Surg, Rochester, MN USA