[1] Uniformed Serv Univ Hlth Sci, Dept Med, Bethesda, MD 20814 USA
[2] Walter Reed Natl Mil Med Ctr, Div Gastroenterol, Bethesda, MD 20889 USA
[3] Uniformed Serv Univ Hlth Sci, Dept Pathol, Bethesda, MD USA
[4] Walter Reed Natl Mil Med Ctr, Dept Pathol, Bethesda, MD USA