1. Institute for Quality and Efficiency in Health Care (IQWiG); Department of Non-Drug Interventions; Dillenburger Str. 27 Cologne Germany 51105
2. University of Witten/Herdecke; Institute for Research in Operative Medicine; Ostmerherimer Str. 200 Cologne Germany 51109
3. University of Heidelberg; Department of General, Visceral and Transplant Surgery; Im Neuenheimer Feld 110 Heidelberg Germany 69120
4. Gasthuisberg University Hospital, Katholieke Universiteit Leuven; Department of Abdominal Surgery; Leuven Belgium 3000