Donors can have their own agendas, too. The academic literature on donor psychology offers many examples, like a man who sought the adulation of his community by offering a kidney to his minister, a daughter who competed with her own mother to be the rescuer of another family member and a woman who told researchers that her motive for wanting to give a kidney to a stranger was to become “‘Daddy’s good girl.” Then there is the “black-sheep donor,” a wayward relative who shows up to offer an organ as an act of redemption, hoping to reposition himself in the family’s good graces. For others, donation is a sullen fulfillment of familial duty, a way to avoid the shame and guilt of allowing a relative to suffer needlessly and even die.

By comparison, friends are better insulated from emotional pressures; their compassion is less likely to be tinged with obligation, let alone tainted by it. And the rare Good Samaritan donor who cold-calls a transplant center to donate to the next suitable person in the queue, not even knowing who will get his kidney, surely embodies the purest form of altruism. In the end, though, people who don’t want to donate usually manage to extract themselves. They miss appointments for screening tests or just drop out of the process.

People who actually do become donors, however, usually regard it as a supremely gratifying experience: they were given a blessed opportunity to save a life, a chance that relatives of a dying cancer patient can only dream of. I’ve read of siblings jousting to give an organ to a cherished parent and of adult children who were heartbroken when doctors ruled them out on medical grounds. According to a review of published surveys on donor attitudes by Mary Amanda Dew, a psychologist as the University of Pittsburgh Medical Center, about 95 percent of donors say they would do it again. Most experience a boost in self-worth and enjoy feelings of deep purpose, while only a small minority regret having donated or report that their relationships with recipients changed for the worse.

From my medical training, I was familiar with some of the ins and outs of end-stage renal disease. I had an especially morbid dread of dialysis. The playwright Neil Simon received a kidney from his longtime publicist in 2004  “The Odd Donor Couple,” as The New York Times put it  but before that he endured 18 wretched months on dialysis, suffering cramps and vomiting spells that kept him largely confined to his house. His memory deteriorated, and he hated the time away from his writing. Shortly before his donor came forward (unsolicited, it should be noted), Simon’s doctors said he might have to start spending more time on dialysis. If that were necessary, he said, he had decided, “I didn’t want to live my life anymore.” Neither, I thought, would I.

It is possible that I was overestimating how miserable I would be on dialysis. An avalanche of psychological data shows that people are far better at handling adversity when it actually befalls them than they expect they will be. Still, I was quite sure I would flout the longstanding evidence attesting to human adaptability. On dialysis I would be disconsolate and maybe even suicidal if the wait for an organ were to stretch for years. As dispiriting, I would lose all my friends. Not that I expected them to abandon me. I would abandon them out of anger for not rescuing me.

By the end of the summer of 2005, a year after the diagnosis, there was no donor in sight. I was mentally preparing myself to undergo the standard predialysis operation to create “access” to the machine. A vein and artery in my arm would be joined to create a large superficial vessel for the insertion of needles and tubing that would carry my blood to and from the machine. I resisted, but I knew that soon I wouldn’t be able to put off dialysis any longer.

The “tyranny of the gift” now took on a new meaning for me. It was no longer about moral debt; it was about the very fact that an organ had to be a gift, about the tyranny of the system. I heard of people trying to persuade strangers to give them organs. They put up bulletin boards or started Web sites (GordyNeedsAKidney.org, whose opening page carried the plaintive headline, “Please Help Our Dad”). I flirted with the idea of becoming a “transplant tourist” in Turkey or the Philippines, where I could buy a kidney. Or going to China, where I would have to face the frightful knowledge that my kidney would probably come from an executed prisoner. Grim choices, but I was afraid I could die on dialysis if I didn’t do something to save myself.