By LIZ SADLER and RITA DELFINER

He went behind his mom's back to save her life.

Anthony Ciambrone's 71-year-old mom, Betty, was stricken with kidney disease after a bout with high blood pressure.

When the North Merrick, LI, woman was told that she needed a transplant, Anthony, 42, volunteered.

His mom didn't want him to go through surgery, but Anthony pulled a fast one.

"I kind of went behind her back and spoke to the doctors," said the Elmont school custodian.

"There's a very long wait list and I was basically told she really didn't have that much time to wait.

"It really wasn't a hard decision."

Tests revealed that his kidney was a match, and the transplant surgery took place last June.

"I don't know how to thank him for the rest of my life," said Betty Ciambrone, who no longer has to go through a grueling dialysis routine.

"Last winter, I couldn't even walk in the snow. This year, I went out and shoveled three times," she added.

Betty was among three sets of miracle moms and selfless sons who spoke yesterday at North Shore University Hospital's Transplant Center in Manhasset, where the surgeries were performed last year.

Dr. Ernesto Molmenti, the doctor who performed all three transplants, said that "the best way to celebrate this Valentine's Day is to see these three beautiful mothers with their three handsome sons who volunteered to give a kidney to them to make their lives so beautiful."

He said parents generally initially turn thumbs-down on accepting a kidney from an adult child and "we have to give a message that it's all right for children to give a kidney to their parents, that it's perfectly normal to live with one kidney."

For NYPD Sgt. Nicole Dean, 45, of Jamaica, Queens, a Police Academy instructor, the shocking news that she had kidney disease and needed a transplant came in August 2008 during a routine physical.

Her whole family volunteered to help out, but she chose her oldest son, Dominick, 24, a salesman at a Long Island car dealership.

"I would never expect in a million years that . . . I would give him life and raise him and now he has given me a better quality of life," said Dean, who had the transplant in March and now feels "great."

Dominick Dean said "the older son is like the protector. Even though they run to their mother when something goes wrong, they still feel, 'If I can help her, if I can do this' . . . so of course, I had to step up."

Kathleen Geiger, 55, of Northport, had a kidney transplant a decade ago, but was in desperate need of a new one last year. Dennis, 28, of Manhattan, the eldest of her three sons and a research analyst at a hedge fund, said he had the "privilege" to be the donor.

"You feel a little selfish taking a kidney from your son, but he volunteered and never complained about anything," his mother said.

The transplant took place in June -- two months before Dennis was set to walk down the aisle -- but the Geigers were able to dance together at his wedding.