Department of Surgery, Academic Medical Center, Amsterdam, The Netherlands. Department of Surgery, University Medical Center Utrecht, Utrecht, The Netherlands. Clinical Research Unit, Academic Medical Center, Amsterdam, The Netherlands. Department of Gastroenterology and Hepatology, Academic Medical Center, Amsterdam, The Netherlands. Department of Surgery, Gelre Hospital, Apeldoorn, The Netherlands. Department of Gastroenterology, Gelre Hospital, Apeldoorn, The Netherlands. Department of Dietetics, Gelre Hospital, Apeldoorn, The Netherlands. Department of Surgery, Hospital Gelderse Vallei, Ede, The Netherlands. Department of Gastroenterology, Hospital Gelderse Vallei, Ede, The Netherlands. Department of Surgery, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands. Department of Gastroenterology, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands. Department of Gastroenterology and Hepatology, University Medical Center Utrecht, Utrecht, The Netherlands.