Dr Jason On Wei Ji is a consultant surgeon who specialises in managing colorectal cancers and complex polyps. He offers advanced robotic, laparoscopic, and minimally invasive surgical techniques.

He completed his specialist training in the North of Scotland before undertaking the Northern Laparoscopic Colorectal Fellowship at the Royal Victoria Infirmary and the Freeman Hospital in Newcastle, and separately, at the Queen’s Medical Centre in Nottingham. This combined experience enabled him to further refine his expertise in complex minimally invasive colorectal surgery. 

Dr On was appointed consultant at the Aberdeen Royal Infirmary, where he received training in robotic surgery. He has since performed over 100 robotic colorectal resections. He is a core member of the colorectal cancer and complex polyp multidisciplinary teams. He also provides colorectal support for neuroendocrine tumours (NET) management. In addition, he served as the clinical lead for the colorectal cancer vetting pathway.

Dr On holds a Diploma in Medical Education from the University of Dundee and is engaged in teaching and training of surgical trainees, medical students, physician associate students, and surgical first assistants. He contributes to several surgical training programmes and serves as a faculty member on internationally recognised courses including the European Association for Endoscopic Surgery (EAES) course on minimally invasive colorectal surgery. He also co-organised the first robotic colorectal cadaveric training course in Aberdeen. In addition, he sits on both the shortlisting and interview panels for the national selection of higher surgical trainees, as well as on the panel for the annual review of competence for surgeons in training. He also supervises final-year medical students at the University of Aberdeen during their electives, overseeing their projects through to completion.

Dr On is also involved in clinical research with publications in surgical journals. In Aberdeen, he served as the local lead principal investigator for the LaCeS2 trial, co-principal investigator for the EXTEND trial, and co-investigator for the NAIAD study. He also serves as a reviewer for multiple international journals.

Outside of work, Dr On enjoys spending time with his wife and daughter. In addition to his professional interest, he expresses his creativity through photography and piano.

Publications
1) Towards safer colorectal surgery worldwide: Outcomes and benchmarks from the ESCP CORREA 2022 audit. Colorectal Dis. 2025; 27:e70281

2 ) On, J., Shim, J., Mackay, C., Murray, G., Samuel, L., Parnaby, C. and Ramsay, G. (2021), Pathological response post neoadjuvant therapy for locally advanced rectal cancer is an independent predictor of survival. Colorectal Dis, 23: 1326-1333. https://doi.org/10.1111/codi.15512

3) Pine, J., Stevenson, L., On, J., (2020), Intestinal stomas, Surgery (Oxford), Volume 38, Issue 1, Pages 51-57

4) On J, Shim J, Aly EH. Systematic review and meta-analysis on outcomes of salvage therapy in patients with tumour recurrence during 'watch and wait' in rectal cancer. Ann R Coll Surg Engl. 2019 Sep;101(7):441-452. doi: 10.1308/rcsann.2019.0018

5) On, J., Aly, E.H. ‘Watch and wait’ in rectal cancer: summary of the current evidence. Int J Colorectal Dis 33, 1159–1168 (2018). https://doi.org/10.1007/s00384-018-3116-5

6) Richards C, Ventham N, Mansouri D on behalf of The Scottish Surgical Research Group, et al An evidence-based treatment algorithm for colorectal polyp cancers: results from the Scottish Screen-detected Polyp Cancer Study (SSPoCS) Gut 2018;67:299-306.