The Commission for Health Improvement is unlikely to use its investigative 'teeth' in the first high-profile medical 'blunder' to come to light since its inception.
Carmarthenshire trust has ordered an internal inquiry and an investigation by the Royal College of Surgeons into the removal of the wrong kidney from patient Graham Reeves at Prince Philip Hospital in Llanelli, west Wales.
The surgeon in charge of the case, John Roberts, and his surgical team have been suspended from operating. Mr Reeves is still in intensive care at Morriston Hospital, Swansea.
CHI communications manager Diane Jakubowska said: 'There is probably no need for CHI (to take up the case) because the hospital has taken very positive steps itself.'
She admitted: 'We are developing as we go - a lot of our staff are on secondment, so while we are not exactly making it up as we go along, it is taking a while to talk things through.
'It just depends on so many factors - what our capacity is, for one. After year one we will be more able to offer a more coherent vision.'
Mark Emberton, assistant director of the Royal College of Surgeons' clinical effectiveness unit, cautioned against over-reacting to incidents like the kidney error which 'probably only happen about once a decade'.
He said: 'Almost certainly the inquiries will find that this came down to human mistakes that are normally picked up by the processes in place. The fact that these events happen so rarely shows that these procedures are very robust.'
But Liz Thomas, assistant director of Action for Victims of Medical Accidents, suggested that while a 'blatant error - where the effects are critical' - would come to public attention, it might represent the 'tip of the iceberg' of more widespread systems failures.
She urged the government to follow up a pilot study by University College London's clinical risk unit.
The study of 480 patients at north London's Whittington Hospital, found that 6.7 per cent of admissions were marked by adverse events caused by medical mismanagement.