1. Department of Gastroenterology, St Mark's Hospital, Northwick Park, Watford Road, Harrow HA1 3UJ, UK
2. Department of Radiology, St Mark's Hospital, Northwick Park, Watford Road, Harrow HA1 3UJ, UK
3. Department of Surgery, St Mark's Hospital, Northwick Park, Watford Road, Harrow HA1 3UJ, UK