John Furdyna hadn't talked to Gerard Rozycki since they graduated from Reading Central Catholic High School in 1979.

They had never been close friends. But in October, Furdyna learned through a mutual Facebook friend that Rozycki needed a kidney. So he offered one of his.

When their blood types were deemed incompatible for direct donation, they joined what is known as a kidney chain.

It made Furdyna an even better Samaritan: On May 30, surgeons at the Hospital of the University of Pennsylvania removed one of his kidneys and sent it to a patient in Wisconsin. Another patient, at Penn, gave a kidney to Rozycki in return.

Kidney chains transfer organs like falling dominoes. An "altruistic donor" - someone with no link to anyone in need - starts the chain by offering a kidney. It goes to someone who has lined up a donor with whom she is incompatible - and whose kidney then goes to yet another person with an incompatible donor. And so, the chain stays in motion.

The two Reading men were among four patients at Penn - two giving and two receiving - who participated in what the National Kidney Registry says is the second-largest kidney chain ever in the United States. In just 36 days, 28 kidneys were removed and transplanted into 28 recipients.

A growing number of chains are being coordinated across the country. They are improving the outcomes of transplants and helping limit the growing gap between kidney supply and demand.

More than 97,000 people now await kidneys, compared with 78,000 five years ago, according to the Organ Procurement and Transplantation Network; 10 percent die on the wait list every year.

Furdyna, 52, and Rozycki, 51, were part of what organizers at the National Kidney Registry named Chain 221, based on how many have been attempted. It involved 19 centers in 11 states.

When Rozycki's kidneys started failing two years ago due to a genetic condition called Alport syndrome, physicians put him on the wait list. In March, his kidneys performed so poorly he received peritoneal dialysis, a type he could do at home but that required eight hours every day.

"Once you're on dialysis, you're on it for life," Rozycki said. "I was hoping I could get a live donor somehow, some way."

According to a paper published last year, 30 percent of patients with a living donor are unable to accept that donor's kidneys.

"It's not just about spending less time on dialysis or on the wait list, but about improving survival," said Peter Abt, who performed one of the Penn surgeries. Transplant patients with kidneys from living donors survive for 18 to 19 years, on average, about twice as long as those with deceased donors, he said.

Kidney chains are particularly useful for patients whose genetics make finding a match difficult. That was the case for 10 patients in Chain 221, including the recipient of Furdyna's kidney.

But difficult patients offered to chains by hospitals outnumber easily matched patients, said Alvin Roth, a professor of economics at Stanford University. He said hospitals handle their own easy patients rather than pay a fee to the registry to coordinate the chain.

Roth worked closely with Itai Ashlagi of the Massachusetts Institute of Technology, along with a team of computer scientists and hospital workers, to develop the algorithm used for setting up kidney chains. It helped Roth win a Nobel Prize last year.

A challenge to keeping chains going is that donors drop out. Since the registry completed its first chain in 2008, however, the number of broken chains has declined, from 33 percent to zero this year. And the number of completed chains is on the rise, with 13 since Jan. 1.

Although other groups also use chains, the registry holds the record with 709 recipients. Still, that is just a drop in the bucket compared with the tens of thousands of kidneys transplanted over the last five years. And only 4.7 people, on average, received kidneys in each of the registry's chains.

Paige Porrett, who performed Rozycki's surgery, estimates Penn has been involved in about 20 kidney chains. Porrett and others anticipate more people will sign up to be altruistic donors.

Being a live donor involves a significant time commitment. Donors, for example, are required to provide samples whenever a potential recipient is found.

"I was nervous," Furdyna recalled of his first appointment. "I had this whole jug of urine driving down, thinking, 'Why am I doing this?' "

Risks are the same as for any major surgery. They include bleeding, infection, and, in less than 1 percent of cases, death. Recovery may take months.

But possible complications should not deter people from becoming altruistic donors, said Steve Mulroy, a law professor at the University of Memphis whose donation - inspired by an episode of The Simpsons, in which a hospitalized Homer spies his next-door neighbor on a gurney, ready to donate a lung and kidney - started Chain 221 on April 30.

"In law school, we learn something called the Hand formula," Mulroy said. "It's a way of assessing risks and benefits. If you're worried about a potentially bad thing happening, you multiply the magnitude of loss by the probability of it actually happening. There's such a low risk of serious mishaps with kidney donations, I can't imagine making a different decision."

Furdyna has been back producing studio television for weeks. Rozycki won't return to work at a steel mill until the end of August, but that hasn't stopped him from his side operation of baking cheesecakes.

"Yeah," Rozycki said, "you don't expect a steel mill worker to be making cheescakes, do you?"

Contact Leila Haghighat at 215-854-4869 or lhaghighat@phillynews.com.