A surgeon at a hospital in Worcester, Massachusetts, is alleged to have performed an operation on the wrong patient, removing their kidney.
The incident is understood to have taken place within the past few weeks at Worcester's St. Vincent Hospital.
Erica Noonan, a spokeswoman for Tenet Health, which owns the hospital, said: "This is a deeply unfortunate situation involving a patient misidentification that took place outside of our hospital and did not involve our employees.
"Our staff followed proper protocols in preparing for and performing the surgery, which was scheduled by the patient's physician at our hospital.
"Saint Vincent Hospital is committed to providing safe, high-quality care to every patient who enters our doors. We are saddened that this incident occurred and our leadership continues to assure the individual receives the support and care needed."