[1] McGill Univ, Ctr Hlth, Div Gastroenterol, Montreal, PQ H3G 1A4, Canada
[2] McGill Univ, Ctr Hlth, Dept Clin Epidemiol, Montreal, PQ H3G 1A4, Canada
[3] Univ Dijon, Dept Vasc & Intervent Radiol, Sch Med, F-21004 Dijon, France
[4] Chinese Univ Hong Kong, Inst Digest Dis, Hong Kong, Hong Kong, Peoples R China