Almost 2000 colonoscopy patients at health services along the Victoria-NSW border may have the procedure repeated, after an investigation into their surgeon.
Public and private patients from the Albury-Wodonga area who were in the care of doctor Liu-Ming Schmidt will be contacted in coming days.
Safer Care Victoria expected many of them would need to have another colonoscopy as a precaution over a "low" risk they could have cancer.
A panel of experts reviewed procedures involving Dr Schmidt at Albury Wodonga Health, Albury Wodonga Private Hospital and Insight Private Hospital from 2018 to 2022 after one of her colleagues raised concerns.
It found some colonoscopies she supervised or performed were incomplete.
"The results potentially were inaccurate," Albury Wodonga Health chief executive William Appleby told reporters on Thursday.
"This is a difficult and distressing time for all 2000 patients and their families and we are deeply sorry for their experience.
"This is not the standard of care that they deserve. Nor is it the standard of care that we expected to deliver."
Victorian Chief Surgical Advisor Ben Thompson said there was a low risk some patients went on to develop undetected cancer.
"That would be our greatest concern for these patients, that there's a risk that a cancer might have been missed," Professor Thompson said.
The review also looked at other procedures Dr Schmidt was involved with, but no other issues were raised.
In December 2022, an inquest examined the death of one of her patients, William Edmunds, who died following complications after a procedure to remove part of his bowel.
Mr Appleby said that matter was unrelated to concerns raised about colonoscopies.
Dr Schmidt is a registered medical practitioner but has now been suspended from three health services in the Albury Wodonga region and relevant medical bodies have been notified.
A review by Safer Care Victoria led to a recommendation to strengthen leadership at Albury Wodonga Health and other measures.
The organisation's chief executive Mike Roberts said lessons would be learnt and shared across health services.
"This is an exceptional circumstance, absolutely exceptional," Professor Roberts said.
"I want to provide assurance that the health system across Victoria and NSW is a safe system.
"It is clear, however, that something has gone wrong in this situation."
Every patient will be offered counselling and follow-up care.
It's expected urgent cases will be seen by an independent clinician within 30 days and non-urgent cases will be seen in the next six to 12 months.
Colonoscopies are often used to detect bowel cancer and patients affected can contact Cancer Council Victoria with any queries.
Shine Lawyers said any impacted patients who were diagnosed with cancer could seek independent legal advice about whether they would be entitled to compensation.
The Australian Medical Association and Medical Council of NSW said they were unable comment.