Northampton Hospital: Bung left in gynaecological patient
Surgical staff left medical equipment in a patient undergoing a hysterectomy at a hospital in Northamptonshire.
The bung was left in place after the procedure at Northampton General Hospital.
A report which went before the hospital's public trust board said the patient was discharged home and the bung fell out four days later.
The hospital has apologised for the incident and said it had learned from the error.
It was one of two "never events" to happen at the hospital in Cliftonville in 2016.
A hospital spokesman said details could not be given of the second incident - that happened in January - due to confidentiality reasons but it was described as "wrong site surgery" in July's report.
The spokesman said: "Almost 80,000 procedures are performed annually by our medical and nursing staff.
"We are committed to providing each and every one of our patients with a high level of safe care and are deeply sorry that, in these two cases, a vital aspect of the care provided fell short of the standard we would expect.
"We don't underestimate the effect of a never event on our patients and our staff. That is why we believe we need to openly tackle these issues on the rare occasions they occur.
"We have undertaken thorough investigations into the circumstances surrounding each of these never events and reported them to the Care Quality Commission, NHS England and our commissioners.
"As a result of our investigations we have improved our theatre reporting and recording systems."