John Roberts and Mahesh Goel carried out the operation

Speaking at a General Medical Council (GMC) hearing on Thursday, consultant of 20 years John Gethin Roberts said his "heart sank" when he realised that the patient's healthy left kidney had been removed instead of the diseased right one.

Mr Roberts and his colleague Mahesh Goel are accused of serious professional misconduct in connection with the operation on 69-year-old Korean war veteran Graham Reeves at Prince Phillip Hospital in Llanelli in February 2000 . They both deny the charges.

Leighton Davies QC for the General Medical Council has described the medics' negligence as "abject, needless and inexcusable".

On the fourth day of the hearing, Mr Roberts explained that he collected x-rays and noted on the theatre operating list that Mr Reeves was to undergo a left nephrectomy - a mistake.

He then helped prepare Mr Reeves for the surgery, which was carried out by Mr Goel.

My credibility with myself has been very severely dented by this procedure John Gethin Roberts

Usually, he said, they would study the x-rays together "but for some reason we did not follow our usual practice".

The GMC was told that he realised something had gone wrong when, two hours after the surgery, the consultant anaesthetist told him that the 69-year-old had not produced any urine.

"My heart sank and I began to realise we had removed the wrong kidney," he said.

"I reviewed the x-rays again and came to the conclusion, I could not understand why, that I previously decided the left (kidney) was correct."

"Because a second view made it obvious the nephrectomy should be the right side."

'Rescue'

Graham Reeves died in March 2000

Mr Roberts then tried to "rescue" the organ so that it could be replanted but it had been put in sterilising agent and was not an option.

An attempt to get Mr Reeves' diseased remaining kidney to work was also doomed.

"The biggest difficulty I have in this case is that I followed my usual practice - except for not going through it with my registrar - and became convinced the left side was the correct side.

"My credibility with myself has been very severely dented by this procedure," he added.

Mr Reeves died five weeks later in March 2000.

The doctors were cleared of manslaughter at a subsequent trial at Cardiff Crown Court in June 2002. The prosecution's case collapsed after pathologist Dr Andrew Davison, told the court he could not be sure Mr Reeves died as a result of the mistake.

The hearing was delayed on Monday after Mr Goel - now living in India - failed to turn up.

But following legal arguments it was decided that it should go ahead without him.

The hearing continues.