Department of Surgical Sciences, Uppsala University, Uppsala, Sweden. Centre for Clinical Research, Uppsala University, Västerås, Sweden. Department of Surgery, Västmanland County Hospital, Västerås, Sweden. Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden. Division of Surgery and Interventional Science, University College London, London, UK.