Professor Siwan Thomas-Gibson MBBS BSc FRCP MD

Consultant Gastroenterologist
Professor Siwan Thomas-Gibson

Professor Siwan Thomas-Gibson MBBS BSc FRCP MD

Consultant Gastroenterologist


Dr Siwan Thomas-Gibson is a gastrointestinal endoscopist and luminal gastroenterologist. She has been a consultant at the hospital since 2006 and is the deputy director of the Bowel Cancer Screening unit. She was Clinical lead for the department from 2011-2016. Siwan was appointed to the prestigious post of Chair of JAG from January 2017 to January 2020, overseeing the quality of endoscopy services and training throughout the UK.

Her specialist interests include the prevention, diagnosis and endoscopic management of pre-cancerous colonic lesions, both as a screening procedure but also in patients with inflammatory bowel disease and those at increased risk of developing colorectal cancer. She specialises in advanced endoscopic imaging and complex therapeutic endoscopy including polypectomy, endoscopic mucosal resection, colonic stricture dilation and colonic stent insertion. She is developing innovative minimally invasive techniques in collaboration with her surgical colleagues. She co-leads a service caring for patients with gastrointestinal symptoms as consequence of cancer treatment.

A significant part of her role in the department is devoted to postgraduate education and training of endoscopists. Her work in the area of training in colonoscopy aims to improve the quality and standard of care to all patients undergoing endoscopic examination.
Dr Thomas-Gibson represents the hospital at numerous national and international meetings. In 2002 she was awarded the John of Arderne medal by the Royal Society of Medicine’s coloproctology section for her research work. In 2006 she gained an MD for her work in ‘Improving Training and Assessment in Colonoscopy’. This work has generated a number of scientific papers and book chapters. She is regularly invited to speak on issues concerning the improvement of colonoscopy standards; teaches national and international trainees attending endoscopy hands-on, therapeutic and lecture courses. She is actively involved in research and development in endoscopic training. She is a member of the British Society of Gastroenterology and represents the unit at the World Endoscopy Organisation, and Dean of St Mark’s Academic Institute.

Dr Siwan Thomas-Gibson is a specialist endoscopist, Dean of St Mark's Academic Institute and luminal gastroenterologist; she has been a consultant at St Mark's Hospital since 2006.


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St Mark’s Hospital

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