[1] CMN Siglo XXI, Lab Gastrohepatol Res, Mexican Inst Social Secur, Mexico City, DF, Mexico
[2] CMN Siglo XXI, Dept Gastroenterol, Mexican Inst Social Secur, Mexico City, DF, Mexico
[3] Inst Politecn Nacl, Super Sch Med, Mexico City, DF, Mexico
[4] Vanderbilt Univ, Div Gastroenterol Hepatol & Nutr, 221 Kirkland Hall, Nashville, TN 37235 USA
[5] Med Sur Clin & Fdn, Mexico City, DF, Mexico