The Royal College of Surgeons of England carried out a review of the hospital after concerns were raised about the standards of staff working in the general surgery unit.
NHS Grampian bosses requested an audit after it emerged that there had been a “dramatic breakdown” in team-working within the department.
The probe centred mainly on surgery carried out on patients with gallbladder and liver problems and involved checking sixteen sets of clinical records.
NHS Grampian initially refused to release the full report but has now released information under the Freedom of Information Act.
It reveals that some operations had been unnecessary and carried out as a result of “questionable” decision-making.
The report states: “In seven cases the decisions made about treatment were entirely reasonable, and the outcomes for patients were as good as could have been achieved. In a further three cases the procedures selected were less common or radical approaches which not all surgeons would have chosen.
“Four of the cases involved what could in retrospect be seen as questionable decision-making about pursuing further surgical treatment instead of more conservative or palliative care. With the benefit of hindsight, the surgical treatment of these patients may not have been in their best interests.”
The review team also concluded that patient care could be affected in future if no major changes were made at the hospital.
Malcolm Wright, chief executive of NHS Grampian, said the unit has improved since the report was published in November 2014.
He said: “What is within the review really highlights the fact that the department of general surgery faced a range of very serious issues around team-working, individual behaviours and the potential to impact on patient care.
“The Royal College report provided a springboard for a great deal of the positive progress we’ve made over the last year and a half.”