[1] Univ London Imperial Coll Sci Technol & Med, Surg Epidemiol Trials & Outcomes Ctr, London, England
[2] Univ London Imperial Coll Sci Technol & Med, St Marks Hosp, Dept Surg, London, England
[3] Univ London Imperial Coll Sci Technol & Med, Chelsea & Westminster Hosp, Dept Surg, London, England
[4] Univ London Imperial Coll Sci Technol & Med, Dr Foster Hlth, London, England
[5] Univ London Imperial Coll Sci Technol & Med, St Marys Hosp, Surg & Canc, London, England
[6] Univ London Imperial Coll Sci Technol & Med, St Marys Hosp, Dept Gastroenterol, London, England