Metal forceps were left inside a patient in a so-called never event at a Worcestershire hospital.
The error occurred during a complex seven-hour abdominal operation at Alexandra Hospital on 23 November.
The patient spent the night in intensive care at the site in Redditch when the six-inch (15 cm) object could not be retrieved the same day.
The hospital trust has apologised unreservedly and said it would share the findings of an investigation.
The instrument was an arterial clamp resembling a large pair of scissors.
Under normal circumstances, all instruments should be counted and checked twice before the patient is closed. There is also a process of "signing out" at the end of an operation to confirm they are all accounted for.
A source claimed such an incident - known as a never event - should not be able to happen.
It was also claimed that nothing like this had happened at the hospital for at least 15 years.
The BBC understands that following the lengthy operation, the device was found to be missing and was confirmed to be inside the patient, via x-ray, while they were still under anaesthetic.
When it was not possible to remove the forceps, the patient was transferred to intensive care overnight.
A further operation was carried out the next day to remove the clamp and the patient returned to intensive care where they were described as stable.
https://www.bbc.co.uk/news/uk-englan...ester-64075014
