[1] Western Gen Hosp, Gastrointestinal Unit, Edinburgh EH4 2XU, Midlothian, Scotland
[2] Univ Roma La Sapienza, Gastroenterol Unit, I-00185 Rome, Italy
[3] Univ Edinburgh, Gastrointestinal Unit, Ctr Genom & Expt Med, Edinburgh, Midlothian, Scotland
[4] Western Gen Hosp, Dept Radiol, Edinburgh EH4 2XU, Midlothian, Scotland