[1] Univ Coll London Hosp, Gastrointestinal Serv, London, England
[2] Univ Hosp Zurich, Div Gastroenterol & Hepatol, Zurich, Switzerland
[3] Klin Arlesheim, Digest Function Basel, Lab & Clin Motil Disorders & Funct Gastrointestin, Ctr Integrat Gastroenterol, CH-4144 Arlesheim, Switzerland