[1] VA Palo Alto Hlth Care Syst, Gastroenterol Sect, Palo Alto, CA 94304 USA
[2] VA Palo Alto Hlth Care Syst, Otolaryngol Head & Neck Surg Sect, Palo Alto, CA 94304 USA
[3] Stanford Univ, Sch Med, Stanford, CA 94305 USA
[4] Univ Nebraska, Dept Med, Div Gastroenterol, Omaha, NE 68182 USA
[5] Univ Michigan Hosp, Dept Med, Div Gastroenterol, Ann Arbor, MI 48109 USA
[6] Dallas Diagnost Assoc, Dept Med, Div Gastroenterol, Dallas, TX USA
[7] Boston Univ, Med Ctr, Dept Med, Div Gastroenterol, Boston, MA USA
[8] Dartmouth Hitchcock Med Ctr, Dept Med, Div Gastroenterol, Lebanon, NH 03766 USA
[9] Univ Louisville, Dept Med, Div Gastroenterol, Louisville, KY 40292 USA
[10] Univ Calif San Francisco, Dept Med, Div Gastroenterol, San Francisco, CA 94143 USA
[11] Rochester Gastrointestinal Consultant Ctr, Dept Med, Div Gastroenterol, Rochester, NY USA
[12] Rocky Mt Gastroenterol Associates, Dept Med, Div Gastroenterol, Denver, CO USA
[13] Washington Univ, Sch Med, Dept Med, Div Gastroenterol, St Louis, MO USA
[14] Grad Hosp Philadelphia, Dept Med, Div Gastroenterol, Philadelphia, PA 19146 USA
[15] Univ Calif San Francisco, Dept Surg, San Francisco, CA 94143 USA