A healthy kidney was removed from a sick child by mistake, says a hospital in the Republic of Ireland.
Our Lady's Children's Hospital in Crumlin described the operation as an "unprecedented error".
The Dublin hospital said it had given its sincere apologies to the family.
The young child now faces regular dialysis unless a donor kidney can be found. An internal investigation is being carried out by the hospital.
The hospital described it as a "significant and regrettable medical error".
The child has been discharged from the hospital.
The hospital said its board of directors will consider the detail of the review and act where appropriate, BBC reports.
Our Lady's said the family was continuing to receive full support by the hospital staff and were happy to remain there for follow-up care.
Irish Health Minister Mary Harney has indicated there may need to be an outside enquiry, even though she said she had total confidence in the internal review.
She said that unfortunately clinical errors occur in the best healthcare systems.
The Labour Party said the findings of the hospital inquiry must be made public.
The party's Jan O'Sullivan said: "While I would accept that private aspects of this case must remain private, any findings of an investigation that indicates that there may have been systems failures or other shortcomings, should be published.
"The parents of this child, as well as parents of other children who are being treated for similar conditions in the hospital, need reassurance that this kind of incident does not recur."