Surgeons at a Devon hospital left part of a shattered scalpel blade inside a cancer patient after it broke during an operation last year.
Derriford says it would have been dangerous to remove the blade
Consultants at Derriford Hospital in Plymouth decided it would be too dangerous to remove the broken fragment from 59-year-old Frederick Wynn.
Last week the hospital apologised after a 2in scalpel blade was left inside another patient.
The operation to remove a cancerous kidney took place last August.
Mr Wynn from Kingsbridge told the Plymouth Evening Herald: "Knowing that these bits are inside me is just one more heap of worry that I didn't need after having a kidney removed."
Derriford Hospital said the scalpel had been returned to the manufacturer in the US for investigation.
In a statement, the hospital said: "A fragment of metal from a harmonic scalpel, the size of a staple, broke off when Mr Wynn was in theatre, having his cancerous kidney removed.
"The patient, who had already undergone lengthy and complex surgery, would have been at greater risk if the consultant had tried to undertake further complex surgery to remove this piece of metal.
"So the consultant, acting in the patient's best interest, decided that as the tiny piece of equipment would be unlikely to cause Mr Wynn any problems and gristle would form around it, the safest thing to do would be to leave it in situ.
"The piece of metal is no larger than the staples which have to be left in patients to close their blood vessels after surgery."
Last week it was revealed that a scalpel blade had been left inside retired headmaster Victor Hutchison during a heart bypass operation at Derriford.
The blade was not found until three months later, when the pensioner, from Sticklepath, near Okehampton was X-rayed at another hospital after being admitted with gall bladder pain.
A pathologist found the presence of the scalpel blade did not contribute to Mr Hutchison's death, aged 76, from unrelated causes last March.