Video report by Correspondent Jane Loughrey
A public inquiry will be held to investigate concerns around the clinical practice of a former Southern Health Trust consultant.
Consultant urologist Aidan O'Brien retired from his post at Craigavon Area Hospital earlier this year.
The trust notified the Department of Health of concerns in July.
Announcing the inquiry on Tuesday the Health Minister told the Assembly that 1,159 patients' records have initially been reviewed and 271 patients or families have been contacted by the trust.
Robin Swann added: "So far, nine cases have been identified that meet the threshold for a serious adverse incident review and all nine patients and/or their families have been contacted by the trust to inform them of the position in relation to their respective cases," he said.
"A further six cases are currently being reviewed in more detail to establish if those patients have come to harm."
He added: "This emerging situation within the Southern Trust causes me and my department the gravest of concerns. While I remain convinced that the experience of patients who use our health services is overwhelmingly that of a safe and quality service, these incidents regrettably dent the confidence of service users.
"I fully acknowledge this and I will do all that I can to ensure that lessons are learnt, to prevent situations such as these occurring again."
Urologists diagnose and treat disorders of the kidneys, ureters, bladder, prostate and male reproductive organs.
Help & Support
Any urology patient with concerns about their treatment should contact the Southern Trust on 0800 4148520, weekdays from 10am to 3pm.