IStock Photo 8663959 © Hüseyin Tuncer

In January 2009, Apple, Inc. chief executive Steve Jobs took a leave of absence, citing health reasons. In June, news leaked that he’d had a liver transplant.

The odds a person will have a liver transplant—which removes a person’s entire liver and replaces it with all or part of a donor’s liver—in a given year are 1 in 47,280. The odds for a man are 1 in 35,230, while the odds for someone in Jobs’ age range, 50-64, are 1 in 15,260.

Jobs’ operation, like all liver transplants, would have taken at least 4 hours and as many as 12. The surgeons take out the diseased liver, put in a whole or partial healthy liver, and meticulously reconnect all the blood vessels and bile ducts. It can take three weeks to be discharged from the hospital and up to a year to fully recover. Transplant recipients have to take drugs for the rest of their lives so their bodies don’t reject the foreign tissue.

People need transplants if they have liver disease so profound that no other treatment will help. The most common cause of that kind of damage is hepatitis C. Bile duct disease, certain inherited diseases, liver cancer, and chronic alcoholism also frequently scar and destroy this critical organ. Jobs had been diagnosed with a rare form of pancreatic cancer in 2004. Some doctors speculated that the cancer spread to his liver, as it does in most of the 75% of patients whose cancers reappear outside the pancreas.

The odds an adult will be diagnosed with liver disease in a year are 1 in 84.25. That’s almost the same as the odds a person 65 or older will be diagnosed with Alzheimer’s disease in a year (1 in 85.14). The odds that someone is currently on the waiting list for a liver transplant are 1 in 18,150.

Not everyone who needs a liver transplant will get one, because there aren’t enough donor organs to go around. Of the 105,000 people currently on a waiting list for organ transplant in the US, about 16,000 need a liver (About 83,000 need a kidney and 3,000 need a heart). But there are only 6,000 liver transplants performed each year—meeting just three-eighths of the demand.

Whether people on the waiting list get the organs they need depends on a lot of factors, including how sick they are, whether there is a match in blood type and body size between the person and the donor, whether the person has a relative or other living match who's willing to donate, and how long the waiting list is in a particular geographical area. While some states have shorter waits than others, the overall odds a person on the waiting list for liver donation has been there for at least five years are 1 in 4.62. About 1 in 21.1 get added to the list each month.

Despite the waiting list, there’s one thing about liver transplants that’s different from all other organ replacements: the surgery can be successful using only half an organ. That means living donors—usually family members—can offer part of a liver to someone who needs one, and it allows for more recipients of a deceased donor’s liver. Within weeks after surgery, the donor's and recipient’s livers grow back to full size. It's the only organ that can do so.

September found Jobs back on stage at a press conference, gaunt but recovering after his April transplant. He now belongs to a group that has about a 75% chance of surviving five or more years. As a billionaire, he has already beaten some long odds. Perhaps, with his fresh liver, he'll do it again.