[1] Mayo Clin, Dept Med, Div Gastroenterol & Hepatol, Rochester, MN 55905 USA
[2] Mayo Clin, Dept Hlth Sci Res, Rochester, MN 55905 USA
[3] Univ N Carolina, Ctr Funct GI & Motil Disorders, Chapel Hill, NC USA
[4] Mayo Clin, Dept Med, Jacksonville, FL 32224 USA