Massachusetts health authorities are investigating an allegation that a surgeon removed a kidney from the wrong patient.

"We are aware of this serious allegation, and are investigating in line with our state and federal authority," according to a statement from the Massachusetts Department of Health, when asked about media reports of the alleged incident at St. Vincent Hospital in Worcester.

"This is a deeply unfortunate situation involving a patient misidentification that took place outside of our hospital and did not involve our employees." according to a statement from Tenet Health, which owns St. Vincent. "Our staff followed proper protocols in preparing for and performing the surgery, which was scheduled by the patient's physician at our hospital."

Tenet Health did not elaborate on how or where the mistaken identification took place.

"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 affected patient receives the support and care needed."

Surgery performed on the wrong patient is described as a "never event" by the Agency for Healthcare Research and Quality: an error that should never occur and indicates serious underlying safety problems.

This kind of "vivid and terrifying" surgical mistake, according to the agency -- when a procedure meant for Mr. Smith is done on Mr. Jones, for example, or when Mr. Smith's right leg is operated on instead of his left leg -- is "relatively rare."

One study found that such errors occur in approximately one in 112,000 surgical procedures, which means an individual hospital would have such an error every five to 10 years.

Looking at a broader range of surgical problems, an estimated 200,000 people died from complications or other postoperative issues involving the 65 million surgical operations performed last year in the United States, according to a report this week in the Harvard Business Review, which looked at innovations in surgical quality and safety.

The Joint Commission (PDF), which accredits hospitals, encourages them to mark the surgical site beforehand and to have a "timeout" just before starting the surgery to confirm that the correct procedure is being done on the correct patient.

While timeouts have been helpful, they haven't solved the problem, said Dr. Peter Pronovost, senior vice president for patient safety and quality at Johns Hopkins Medicine.

The timeout might not work if the patient were given the wrong ID bracelet or if another patient's X-rays were sent to the operating room, he said.