[1] Univ Ulm, Dept Gen & Visceral Surg, D-89081 Ulm, Germany
[2] Donauklinikum, Ctr Oncol Endocrine & Minimal Invas Surg, Neu Ulm, Germany
[3] Ostalb Klinikum, Dept Surg, Aalen, Germany
[4] Univ Ulm, Inst Epidemiol & Med Biometry, D-89069 Ulm, Germany
[5] Red Cross Hosp, Dept Gen Surg, Munich, Germany