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Marilyn never expected that a routine heart exam would cause kidney damage. But it did.
A nurse from Salt Lake City with type 2 diabetes, Marilyn had undergone one angiogram before being diagnosed with heart disease in 1996. Three years later, in November 1999, she found herself facing an unpleasant surprise after going in for her second heart exam. The creatinine in her body rose to an unusually high level, causing her kidney to stop functioning properly.
Consulting Her Doctor
Concerned, Marilyn consulted her cardiologist. It turned out that her diabetes had put her at risk for kidney damage from the dye given during the angiogram. But the interventional cardiologist, the doctor who conducted the test, went ahead with the procedure anyway.
In the end, her kidney regenerated itself, but it took six months to heal.
Her Reason for Concern
Marilyn is worried that the doctors administering the exams are either not aware that their patients have diabetes, or don't think to take the tests in a way that will avoid damage to the kidneys.
"It was scary," said Marilyn about the experience. "Some doctors are not that cognizant. They're not being negligent, but they don't think, 'Is there another way this can be done?'"
The Medical Community Is Aware
According to James T. McCarthy, MD, staff physician at the Mayo Clinic in Rochester, Minnesota's Division of Nephropathy, the risk of kidney damage from dyes is a "widely known fact" among the medical community.
"Doctors make a habit of inquiring with patients if they know about their kidney condition," McCarthy says.
Studies Support the Evidence
Angiograms, which are examinations of the vessels in the heart, are typically taken to detect heart complications. They involve injecting a contrast agent, or dye, into the blood. But, as in Marilyn's case, certain types of contrast agents may cause the body's serum creatinine, a non-protein component of the blood, to increase to above normal levels. The increase can thwart kidney function, and possibly result in the need for dialysis treatment or even death.
Many studies have shown this to be true. One reason, they state, is because type 1 and 2s may have a history of kidney weakness.
In a study published in the July 20, 2000 issue of New England Journal of Medicine (NEJM), researchers say that chances of damage from contrast agents are 50 to 90 percent higher for those who already have severe kidney problems and 9 to 40 percent higher for those with mild to moderate kidney problems. In the book "Brennor & Rector's The Kidney" (fifth edition, 1996, pp. 1686-1687), writers say that the results of tests with animals show that, in most cases, kidney weakness is already present when contrast agents cause damage.
But published literature shows mixed results about how likely it is that damage will occur.
The authors in "Brennor & Rector's The Kidney" cite one study that shows that 50 percent of diabetic patients studied had a toxic reaction to the dye, and another that showed a 38 percent incidence.
History of diabetes, kidney weakness and high creatinine levels before being tested, along with other factors such as age and history of heart failure, all contribute to the risk of damage. This range of variables accounts for the discrepancy between the results of the studies.
Prevention is Possible
As for ways to reduce the chance of damage, options run the gamut.
According to Dr. McCarthy, avoiding the use of a contrast agent altogether is an effective option.
"The general advice is to request an alternative test that can give the same information," he says.
If using a contrast agent is required to get the results they need, McCarthy says that doctors give patients water to avoid dehydration, which is known to keep creatinine levels down.
Researchers in "Brennor & Rector's The Kidney" also recommend giving patients saline (salt solution), urination and using the least amount of dye possible. Some studies they cited showed that using a nonionic dye (one with a low molecular weight) reduced a toxic reaction, but results were inconclusive. In the NEJM report, a preliminary study showed that giving patients a drug called acetylcysteine with water helped maintain low creatinine levels. The drug, however, requires further testing.
What Patients Can Do
Having been on both sides of the fence—as a patient and health professional—Marilyn thinks self-management is the best plan of action. She says that since some doctors don't ask their patients if they have diabetes or don't take the necessary precautions to avoid kidney damage, diabetes patients need to be responsible for informing their doctors.
"That's why it's up to us to be pro-active for ourselves," she says. "And without knowledge we can't be. Unless doctors are made aware of this problem, they might not think about it."
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