1. Department of Surgery, Academic Medical Centre, University of Amsterdam, PO Box 22 700, 1100 DE Amsterdam, The Netherlands
2. Department of Radiology, Academic Medical Centre, University of Amsterdam, PO Box 22 700, 1100 DE Amsterdam, The Netherlands
3. Department of Gastroenterology, Academic Medical Centre, University of Amsterdam, PO Box 22 700, 1100 DE Amsterdam, The Netherlands