More than 400 patients a year may have had the wrong limb or organ operated on, doctors said yesterday at the launch of a guide to eradicate such surgical errors.

More than 400 patients a year may have had the wrong limb or organ operated on, doctors said yesterday at the launch of a guide to eradicate such surgical errors.

Despite being one of the most basic errors in surgery, some patients wake up after an anaesthetic to find they have had the wrong eye operated on or the wrong hip replaced. While there are no official figures, patients have lost their sight, their mobility and their lives as a result.

Hugh Phillips, the president of the Royal College of Surgeons, said: "You might think this is a fairly straightforward exercise [operating on the correct site] but I can assure you it is not because of the large number of people involved in decision making."

A pilot study by the National Patient Safety Agency (NPSA) in 18 NHS acute-care hospitals, found 15 incidents involving wrong-site surgery during a five-month period from November 2002 to April 2003. Extrapolated to the UK that is equivalent to more than 400 incidents a year. Sue Osborn, the agency's chief executive, said the number was tiny compared with the millions of operations performed each year, "but these are 15 individual tragedies and they are 15 too many".

An earlier pilot in 28 NHS trusts found 44 incidents over nine months between September 2001 and June 2002.

The Royal College and the NPSA launched a guide yesterday, described as a "world first", to eliminate the errors. Sir John Lilleyman, the medical director of the agency, said: "Surgery at the wrong site is rare but not rare enough. People operated on the wrong side end up with lawyers."

Margaret Poole, 62, a retired school secretary in Cheshire suffering from cancer, underwent an operation at Leighton Hospital, Crewe, in 1999 to drain fluid from her right lung. The doctor, Kaleem Toori, inserted the needle into her left lung before realising his mistake. He immediately switched but Ms Poole died of a heart attack a few hours later. Dr Toori was later found guilty of serious professional misconduct by the General Medical Council after trying to cover up his error.

In a case from New York, a surgeon had refused to mark up a patient due for heart surgery on the grounds that there was only one of the organ so a mistake was impossible. But the patient was sent to the wrong operating theatre and, in the absence of a mark, ended up having a hernia repair. In a French case, a pregnant woman was confused with another of the same name attending the same gynaecological clinic to have a contraceptive coil removed. The doctor performed the procedure on the pregnant woman and she lost her baby.

Sir John said there were five or 10 cases a year in the UK that resulted in compensation being paid, but there was little data. A review of claims handled by the Medical Defence Union, involving only patients treated in the private sector, found 119 cases over 13 years to 2003 where operations had been performed on the wrong side.

One of the most frequent areas for mistakes was cataract surgery because of the number of operations performed - 250,000 a year - and the pressure to get them done fast. Nick Astbury, the president of the Royal College of Ophthalmologists, said: "As the pace increases with rapid-fire day case surgery the risks increase. The faster we get the more likelihood there is of mistakes being made."

The new guidance calls for clear marking of the body in a standard way in indelible ink while the patient is conscious and a pre-operative checklist to be observed by the whole surgical team. Currently, different hospitals have different styles of marking and surgeons moving jobs have to learn the new style.