1 Department of Upper Gastrointestinal Surgery, Lancashire Teaching Hospitals NHS Foundation Trust, Sharoe Green Lane, Preston, PRC9HT, UK. Electronic address: ishaan.maitra@googlemail.com.
2 Watford General Hospital, West Hertfordshire Hospitals NHS Trust, Vicarage Road, WD18 0HB, UK.
3 The University of Manchester, Manchester Academic Health Science Centre, Lancashire Teaching Hospital NHS Foundation Trust and the University of Central Lancashire, UK.