SAN FRANCISCO (Bloomberg) — Apple Inc. chief executive officer Steve Jobs could be facing surgery to remove his pancreas, doctors say.

Jobs said yesterday he's taking a five-month leave of absence after discovering that his health problems are "more complex" than he thought last week. Apple, which has plunged after a succession of rumours about Jobs' medical condition, dropped 2.3 percent in Nasdaq trading.

Jobs had a procedure similar to a Whipple operation, which involves removing parts of the pancreas, bile duct and small intestine, after he was diagnosed with a rare type of pancreatic cancer in 2004. A potential side effect of this procedure is that the organ has to be removed to prevent pancreatic leak, and the patient has to be kept alive with insulin to regulate blood sugar, said Robert Thomas, head of surgery at the Peter MacCallum Cancer Centre in Melbourne.

"You might have to take the rest of the pancreas out," said Thomas, 66, who first performed the Whipple procedure more than 20 years ago. "You're on significant doses of insulin, and it's not easy to manage. The person has the risk of severe diabetes."

Thomas hasn't treated Jobs and doesn't know details of his condition.

Jobs, who handed day-to-day operations to chief operating officer Tim Cook, said he will remain involved in "major strategic decisions".

Apple's unwillingness to provide details on Jobs' health has frustrated investors, who have watched the stock plummet with each new rumour about his condition. Apple didn't give any details about Jobs' health even as he appeared increasingly thin in 2008, saying only it was a private matter. Jobs said last week he suffers from a "hormone imbalance" that caused weight loss.

Apple, based in Cupertino, California, fell $1.95 to $83.38 in Nasdaq Stock Market trading, after dropping as low as $80.05.

Jobs, 53, said he would remain ceo while taking a medical leave of absence until the end of June. Just last week, Jobs said his treatment should be "simple and straightforward".

"There's been too little information, and the information that's come out has been vague — creating more concern rather than conveying a sense of certainty," said Nell Minow, founder of the Corporate Library, a research firm specialising in corporate governance based in Portland, Maine. "They have achieved confusion, and a sense of being unsettled."

Apple is not providing information beyond the statement, said spokesman Steve Dowling. The company's directors, including former US Vice President Al Gore and Google Inc. CEO Eric Schmidt, either couldn't be reached or declined to comment.

"What they have done is the extraordinary accomplishment of coming out with a press release that is more opaque than the last one," said Jeffrey Sonnenfeld, associate dean of the Yale University School of Management. "They have now surrendered their credibility."

Jobs, who co-founded Apple in 1976, returned as CEO in 1997 after an ouster in the 1980s. He revived the Macintosh computer brand while pushing the company into new markets with the iPod media player and iPhone. He rarely gives interviews and once had a biography of him pulled from Apple's corporate store.

Andy Hertzfeld, one of the main architects of the Mac operating software, wrote in his book that those who worked with Jobs said he was surrounded by a "reality distortion field".

Jobs hasn't been seen in public since October.

"This should not have gone on this long — it's not healthy for the business," said Charles Elson, director of the University of Delaware's John Weinberg Center for Corporate Governance. "The fact the issue has played around for months makes you wonder at the responsiveness of the board."

Jobs disclosed in August 2004 that he had surgery to remove a tumour related to a rare form of pancreatic cancer that wouldn't require chemotherapy or radiation. Cook ran Apple while Jobs took a monthlong leave.

Jobs told Apple's board about his cancer and directors decided to say nothing, Fortune reported in March 2008. Larry Sonsini, the company's attorney, told directors that Jobs' right to privacy topped disclosure rules, the magazine said. Sonsini declined to comment yesterday.