A review of patient records is underway at Rotherham District General Hospital after it emerged a patient waited over a year for an operation.
Experts from NHS England have been called in to check 13,000 records after the discovery of the 66-week wait.
Five other patients have since been found to have waited more than a year for treatment.
The Trust says all the patients had been assessed and their health had not been compromised, but admitted their experience was ‘very poor’.
Chief operating officer, Chris Holt, said: “Following a routine validation of a number of our referral to treatment patient pathways, we identified a patient that had been waiting longer than 52 weeks following referral to the trust.
“We immediately contacted the patient affected to apologise, and put plans in place to ensure they were seen as a matter of urgency.
“In order to make sure this was not a widespread problem, we instigated an immediate review into 13,000 patient records and have so far checked 11,500, and identified five further patients that have been affected.
“We have been in immediate contact with all affected patients to apologise and are making sure they are treated as a priority for the trust.
“This situation has come about as a result of outdated practices that have since been changed.”
The remaining patient record checks at the hospital are expected to be completed by the end of this month.