[1] Johns Hopkins Univ, Sch Med, Div Gastroenterol, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sch Med, Dept Mol & Comparat Pathobiol, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ, Sch Med, Dept Surg, Baltimore, MD 21205 USA
[4] Johns Hopkins Univ, Sch Med, Dept Radiol, Baltimore, MD 21205 USA
[5] Hop Lariboisiere, Dept Digest Dis, F-75475 Paris, France
[6] Cook Endoscopy Inc, Winston Salem, NC USA
[7] Univ Puerto Rico, Dept Med, San Juan, PR 00936 USA