Look what the doctor left behind...

A clamp left inside a patient's chest - (C) New England Journal of Medicine

As the image above shows, surgical instruments are sometimes left inside patients after procedures.

In this case, a clamp was left inside a patient's abdomen.

Researchers say although these are rare medical errors - perhaps one in 19,000 cases.

A study has shown they are more likely to happen in "stressful situations" such as emergency operations, or operations where things change part-way through.

Incidents such as this are rare

Instruments were also more likely to be left behind if the patient was overweight.

Two nurses should count surgical instruments twice before and after operations, but the research suggests this may not have happened in some cases.

'Foreign bodies'

Researchers from Brigham and Women's Hospital in Boston, Massachusetts, suggest X-rays or hand-held scanners could be used to check instruments have not been left behind.

It is rare, but it is serious because it is harmful

Dr Atul Gawande

The researchers looked at medical records of claims or incident reports of a retained surgical sponge or instrument filed between 1985 and 2001 with a large malpractice insurer which represented a third of doctors in Massachusetts.

They found 54 patients had had 61 "foreign bodies" left inside them.

Over two thirds were surgical sponges.

Thirty-seven had to have an operation, and one died.

'Not malpractice

Dr Atul Gawande, who led the research, told BBC News Online: "It is rare, but it is serious because it is harmful.

"But it isn't negligence. We found that teams were following strict procedures to prevent objects being left behind.

"We found its situations in which teams are stressed; emergency operations, or where there has been a change in the operation."

He said counts could be done quickly if staff were under pressure, and missing instruments not picked up.

Dr Gawande said: "I would suggest the problem is not malpractice, it's a process that has a hole in it."

"We could start to use X-rays more liberally in emergency situations to pick things up."

He said hand-held scanners could also be used to pick up missing objects.