n June 14, 2001, doctors at a hospital in Greenville, N.C., undertook what for transplant experts was a routine operation, removing a healthy kidney from one person and placing it another.

The procedure, performed nearly 5,300 times last year in the United States, is widely considered the safest transplant operation. Complications in kidney transplants are considered extremely rare, with only 3 of 10,000 donors dying. Recipients, aided by powerful anti-rejection drugs, enjoy lives free from waiting lists and dialysis machines. Donors, frequently family members, express awe at the knowledge that their gifts mean so much.

It is what my mother, no doubt, prayed for as she underwent surgery on June 14 in Pitt County Memorial Hospital in North Carolina. She would give a kidney to her mentally retarded son, who had lost one organ as a sickly toddler and seen the other start to fail in middle age.

Those who heard about the case marveled at its emotional weight, and at the science that made it possible.

A mother — one at age 69, no less — would give her most fragile child life a second time.

Yet the outcome of the operation quickly doused such optimism. It left those involved wondering about the decisions, medical and personal, that had led up to the surgery.

Today, my brother Joe has the pink cheeks of a successful kidney recipient. This summer, he will take that Caribbean vacation that he had talked about so often before the surgery.

Today, my mother, Barbara, lives in a nursing home, paralyzed on the left side as a result of an extensive stroke that she suffered a day after the surgery. Her brain, so damaged by an errant clot that nearly killed her, has mended enough to allow her a few bursts of words. Most mean nothing. She endlessly repeats, "Bar-Bill," a combination of her name and my father's. Yet she can sing snatches of favorite Rodgers and Hammerstein songs.

Hours after the surgery, Mom had talked of going home — early even — to resume her active retired life in New Bern, N.C.

The urologist who evaluated her as a donor candidate described her in medical records as a "very pleasant, healthy- appearing older white female in no apparent distress." At that point, he told her of the risks of surgery, which included stroke.

When we, her five other children, questioned her decision — "Wasn't she too old?" — she reassured us. And we trusted her, of course. For she was not only Mom, she was Barbara Tarrant, registered nurse, who began her career tending to polio patients alongside Jonas Salk in Pittsburgh and in retirement helped set up a mission hospital in Haiti.

We, her five other children, were busy leading lives across the country when Joe's kidney started to fail. Four of us shared his blood type, meaning we could take the next step in a complicated series of testing to determine a match.

Yet my mother would not hear of it. "It's my duty," she told me.

We trusted her, and we trusted the medical profession that she had served her entire life.

And what was the transplant team thinking in approving an elective surgery on a 69-year-old?

This question fueled my anger after Mom's stroke, and the anger displaced the guilt I felt for not stepping forward first.

I began to dig. Telephone calls, records requests, Internet searches. I exhausted whatever sources of information I could in search of a definitive rule that said donors should be knocked out of contention at, say, 65.

In the end, I found no universal standard that governs all 245 medical centers in the United States that perform kidney transplants.

At U.C.L.A., it is 65, at New York University, 70, and at Fairview-University Medical Center in Minneapolis, 80.

"I don't think there's a straight-up answer," says Dr. Carl Haisch, the North Carolina surgeon who performed Joe's transplant at Pitt County Memorial. He remains perplexed at the outcome with Mom because post-stroke tests show no carotid blockages.

Was her age a factor? Dr. Haisch says he isn't sure, and he hasn't ruled out accepting future older donors.

Today, Joe has moved in with his adored older brother, the teacher and basketball coach. He goes to every game, talks nonstop about the latest ESPN headlines and carefully counts the pills that he must take to maintain a healthy kidney.

He grows quiet when we talk about Mom.