Breast implants do not last forever -- whether they are filled with silicone gel or saline, or whether they were done to reconstruct a breast after a mastectomy or to augment the size or shape of a breast.

Knowing just when that time has come, however, and what to do if you suspect it has, is not always simple.

Sonia Fuentes, 77, of Potomac, Md., a retired attorney and co-founder of the National Organization for Women, encountered that conundrum last year when she suspected problems with the silicone-gel implant she had gotten 15 years earlier after a mastectomy. She thought it had hardened and gotten smaller and feared it was leaking.

She consulted her oncologist, the surgeon who had performed the mastectomy and the plastic surgeon who had performed the implant, and she also scrolled the Internet for background. But opinions and advice were conflicting:

• Get a mammogram to see if the implant has ruptured, one doctor suggested.
• Don't get a mammogram, a women's Web site warned, as the compression could cause the implant to break.
• Have an MRI, the FDA urged on its site, noting that that's the best way to detect a rupture.
• An MRI wasn't necessary, another doctor told her.

"The quality of advice people get is very spotty," said Dr. Scott Spear, chief of plastic surgery at Georgetown University Hospital in Washington, D.C., and immediate past president of the American Society of Plastic Surgeons.

So what's a woman to do?

Anyone concerned about an implant should "start off by seeing a doctor, a plastic surgeon" preferably, Spear said. If the original surgeon cannot be reached or the woman is uncomfortable with the surgeon's opinion, he recommended going to a clinic that specializes in implants or finding a plastic surgeon associated with a university.

That's when Fuentes' saga really began. First she consulted the doctors who had treated her initially. "All of these doctors are top guys," she said. "I had a lot of respect for them." But, she said, two of them "said to me, 'Your breast hasn't changed,' " which she considered "a little presumptuous."

She also was not comfortable with their nudging her to have a mammogram, given what she had read on the Internet and heard from friends.

"You've got to learn to go with your gut," Fuentes said. "But so many women, if a doctor tells them something -- that's it."

Fuentes insisted on an MRI, her doctor relented, and the MRI revealed a ruptured implant.

She asked a plastic surgeon in Cleveland to remove the implant, replace it with a saline version and reconfigure her breasts to ensure symmetry. But she said the surgeon insisted on an ultrasound of the implant beforehand, an option no one else had proposed. It, too, showed a rupture, and the surgery went on as planned.

Dr. Michele Shermak, chief of plastic surgery at Johns Hopkins Bayview Medical Center in Baltimore, said she also uses ultrasound to evaluate implants.

"A mammogram, like any plain film X-ray, is not good at seeing soft-tissue problems," Shermak explained.

For detecting breast cancer, the American Cancer Society recommends regular mammograms, and Shermak indicated that advice should apply to women with and without implants. "Compression should not be a problem" for women with implants, she said.

But for detecting possible rifts in an implant, "mammograms are really not the best way to go," she said.

"Ultrasound is usually the first test that I'll do," Shermak said. She described it as "easy technology" and a test that most medical offices could perform.

"MRI would be the next step," she said. "The MRI is very good, very specific, very sensitive." She described it as "almost too precise in some cases" as it tends to detect "any little thing that looks a little bit abnormal."

In Fuentes' case, however, the MRI and ultrasound were on target. Her surgery took 4-1/2 hours, in part because "the implant had collapsed and had silicone all over it, so it was difficult to remove," Fuentes said she was told by the surgeon.

Saline leaking from a broken implant appears to pose no danger, but opinions differ on the effect of escaping silicone.

If silicone leaks, "the body walls it off," Shermak explained. "The body normally develops scar tissue to things it doesn't see as itself. The scar tissue effectively becomes a shell around the implant."

However, Spear said that "the risk of it even locally causing mischief is pretty low."

Both surgeons said that for any woman unnerved by those thoughts or having other fears about an implant, removing the implant is usually the appropriate option.

"You only need to treat or remove the implant if the patient is symptomatic," Shermak said. "But I would never say 'don't do it,' if that's what the woman wants."