Ct Scans: How to Protect Your Kidneys

Today more and more of us are undergoing CT scans and other medical imaging scans involving intense X-rays.  A new study suggests that we should be taking a pre-scan drug that could protect our kidneys from potential damage.

The inexpensive drug recommended is called N-acetylcysteine.  It can prevent serious kidney damage caused by iodine-containing "dyes" that doctors are using to enhance the quality of the scans.

The "dye" called contrast agent, is usually given intravenously before a CT scan, angiogram or other test. But the new study shows that taking an N-acetylcysteine tablet before receiving the contrast agent can protect patients and that it works better than other medicines that have been proposed for the same purpose.

People whose kidneys are already vulnerable, including many older people and those with diabetes or heart failure, are the most at risk from contrast agents, and have the most to gain from taking the drug.

Mild to moderate kidney damage occurs in one in four high-risk people who have CT scans, and in as many as one in ten people with normal kidney function. In some cases, it causes acute kidney failure.

"Millions of people receive contrast agent each year, including most heart patients who have angioplasties and stents, as well as those having a CT scan. Contrast agent helps physicians see the things we need to see, but it also does pose a hazard to some people," says Kelly. "This drug, which is quick, convenient, inexpensive and widely available, with no major side effects, appears to be the best choice to protect those whose kidneys are most at risk."

And, since most kidney problems cause no symptoms, even healthy people might want to ask their doctors to test their blood creatinine levels before sending them for a scan.

Creatinine levels go up when the kidneys aren't operating efficiently. Contrast-induced nephropathy is defined as a 25 percent or greater increase in creatinine within 48 hours of receiving contrast agent. The new study evaluated the impact of pre-scan medicines by looking at their impact on patients' creatinine levels, as a surrogate for kidney function.

N-acetylcysteine is already widely used to clear mucus in cystic fibrosis patients, and to treat overdoses of acetaminophen. Tablets of prescription-strength N-acetylcysteine are inexpensive about 25 cents for a 500 milligram tablet and stocked by most pharmacies. It has few side effects. Over-the-counter supplement forms of the drug should not be used for pre-scan kidney protection.