[1] Univ Saarland, Dept Gen Visceral & Vasc Surg, D-66421 Homburg, Germany
[2] Univ Ulm, Dept Gen Surg, Ulm, Germany
[3] Univ Helsinki, Cent Hosp, Dept Surg, Helsinki, Finland
[4] Univ Verona, Dept Surg & Gastroenterol, Pancreat Unit, I-37100 Verona, Italy
[5] Univ Bern, Dept Visceral & Transplantat Surg, Bern, Switzerland
[6] Univ Hamburg, Inst Stat & Econometry, Hamburg, Germany