In the subject line of an e-mail message, he wrote: "confidential memo for transplant team members only."
"LET ME CLARIFY ONE ISSUE," he wrote, leading off the April 9, 2004, message with emphatic capitals.
There was no truth to "rumors floating around the hospital and beyond" that he had been turning down offers of donor organs that could have been used to save his patients.
He had refused livers, he said, but only with good reason: if they were from a "marginal donor" or were offered for patients so sick they would never recover. He cited the 2003 case of an extremely ill 40-year-old cirrhosis patient who died six weeks after surgery.
Cao warned the staff against questioning his medical opinion and integrity.
"Anyone who spreads the rumors," he wrote, would be subject to discipline for "professional misconduct" and held "liable, especially if the patients ... find out something and decide to take legal action."
He signed only his last name: "CAO."
The e-mail serves as one strong clue to the meltdown at the liver transplant program, which UCI finally was forced to shut last month.
The hospital was performing so few transplants -- with such poor results -- that it failed to meet federal requirements. The main problem was that the program had been turning down the vast majority of donated livers, many of which were then successfully transplanted into patients at other centers.
Cao's memo -- and the story of his 4 1/2-year stint at UCI -- suggest that the pattern of organ refusals was, in part, a response to the travails of being a small transplant center.
With so much riding on each operation and so few people to bear the responsibility, the program was driven to dysfunction by a paralyzing fear of failure and an obsession for keeping up appearances.
So intense was its aversion to openness that many patients, whose lives swayed in the balance, never suspected anything was wrong until the program was closed, according to interviews and documents.
Cao, who declined to be interviewed for this article, did not create the problems, nor did they disappear when he left -- three months after firing off the April 2004 e-mail.
But his tenure marked a time when all the elements of dysfunction began to coalesce.
"Somebody should have intervened," said Magdi Hanna, a onetime patient of Cao's who waited several months for a liver before giving up on UCI.
"As a patient you are defenseless," he said. "You rely entirely on the integrity of the doctors."
Hiring Cao was a coup for UCI.