The case of Graham Reeves - whose healthy kidney was removed by mistake - has highlighted a rare surgical blunder.

Up to 30 people - including surgeons, radiographers, secretaries and even the patient - are involved in checking that the correct organ is removed during an operation.

Around one million operations are performed on "paired" organs such as kidneys in the UK each year.

Experts say that operating on the wrong organ is extremely rare - with less than one case in a decade.

But mistakes can be made.

Mark Emberton, assistant director of the clinical effectiveness unit at the Royal College of Surgeons and himself a kidney expert, said the process should ensure blunders do not occur.

"These operations require a very long process which starts at the time of seeing a consultant in the out-patients department and a decision is made, left or right," he said.

Paperwork

"It goes through X-rays, radiographers, secretaries, typists, clerical staff, other clinicians, and all those have to make sure the paperwork is correct and stipulates the correct side.

"It culminates between the patient and the doctor and everybody has to agree which side."

The day or morning before an operation, the relevant part of the patient's body is marked with permanent pen.

The patient also signs a form consenting to the operation which states in capital letters which organ is to be operated on.

All the paperwork, including consent forms and X-rays are taken into the operating theatre with the patient.

But Mr Emberton admitted that mistakes can be made.

"Anything between 20 and 30 people are involved from beginning to end and the fact that mistakes are so rare is testimony to the rigours of the procedure," he said.

"Mistakes can occur when a series of things go wrong - for instance, an X-ray being labelled the wrong way or a typing error is made and not picked up.

"The side could be mixed up if it is not known whether the patient is lying face up or face down.

"There are obviously things that can go wrong if the system breaks down and we will have to see if anything can be learnt from this case."