Around 100 patients treated at an independent sector treatment centre have been offered further tests after concerns their procedures may not have been carried out thoroughly.
The patients all had colonoscopies at the Shepton Mallet centre between October 2005 and March 2008.
A patient was later found to have bowel cancer, leading to an independent review of their care. This found that the procedure was not as thorough as it could have been and there were poor views of the colon.
External assessors have since reviewed all 1,828 colonoscopies carried out by the surgeon concerned, who was suspended and has since left the centre. About 100 patients have been advised to have follow-up procedures as soon as possible, around 480 may need follow-ups over the next five years, and 755 patients were advised to talk to their GPs. Another 480 were told no further action is necessary.
Dr Naji Abumrad, medical director of UK Specialist Hospitals, which runs the centre, said: "We believe the thoroughness of the review and the actions we have taken will reassure patients and the public of our commitment to maintain standards."