MRI Health Risks to Kidney Patients Growing with Scan Frequency

August 2, 2010, 10:30AM. By Gordon Gibb

Washington, DCRecent revelations from researchers studying the effects of various MRI health risks, including MRI contrast side effects, further deepen concern over the increasing frequency of MRI procedures by way of the increased availability of MRI machines. With a desire to ensure a proper diagnosis, doctors are ordering MRI scans in rising numbers. And yet, additional scans expose a certain sector of patients--namely, those with kidney disease or renal issues—to increased risk.

That's the conclusion derived from new federal figures that suggest hospitals across the US are administering too many imaging procedures. While MRI (magnetic resonance imaging) does not expose patients to radiation, the same cannot be said for CT scans and X-Ray. While radiation levels are low and deemed not unsafe for an individual scan, the questions surround the cumulative aspect when a patient is exposed to an increasing number of CT scan procedures, for example.

In South Florida, 24 percent of patients who received a chest CT scan at Columbia Hospital in West Palm Beach in actual fact received two, according to a recent report in the Sun Sentinel (Fort Lauderdale): one scan with a contrasting agent, and one without.

While contrast agents used for CT scans have not been the focus of concern recently, those used in MRI scans have been a concern—especially gadolinium-based contrast agents and especially to patients with compromised kidneys. According to the July 20th issue of the Puget Sound Business Journal, 65 percent of all MRI procedures use contrast agents in order to achieve a better image. To that end gadolinium contrast agents are associated with safety concerns with regard to the potential for nephrogenic system fibrosis (NSF) and further MRI kidney damage in patients already suffering from renal failure.

While the risks associated with gadolinium are low provided the MRI contrast agent can be expelled from the body efficiently, patients with kidney failure will not be in a position to quickly and efficiently rid their systems of the gadolinium, without the aid of MRI dialysis.

To that end, Dr. Rodney Ho of the University of Washington has been awarded a $150,000 grant to continue his research into a gadolinium-containing lipid nanoparticle carrier (LNC) that is hoped to deliver improved image contrast at gadolinium levels far lower than those used now.

But even contrast imaging agents deemed more safe, do not make up for the upward spike in MRI and CT scans, and the radiation that results from CT scans specifically. The US Centers for Medicare and Medicaid Services, the federal agency which provided the figures on scanning frequency, noted that CT scans to the chest can expose patients to 133 times more radiation than a simple chest X-ray and can cost $1,000 each.

It's the cost (and revenues) that prompt some doctors to order additional scans, according to un-named researchers in the Sun Sentinel story. This is especially true for doctors having an ownership stake in MRI and CT machines. This, according to past research, which showed a 27 percent to 54 percent increase in scans amongst those medial professionals who stood to achieve some monetary gain from additional scans.

But that's not the only reason. Doctors are increasingly relying on scans not only due to their increased availability, but also to confirm their diagnosis in an effort to avoid malpractice lawsuits.

While imaging achieves that goal for the physician (and for the patient, in the context of the particular malady at issue), it also produces the potential for over-exposure to radiation when a CT scan is involved. It should be noted that health care employees, according to the Sun Sentinel report, observe a maximum annual radiation dose of 20 millisieverts of radiation. However, a 2009 study found that a small but significant percentage of patients—2.1 percent—were exposed to radiation above that benchmark.

There are other concerns with regard to radiation from excessive imaging. Researchers from the Department of Surgical Oncology, University of Toronto, noted in a study published in Nature Reviews Urology that: "Such imaging is not without risk, however, as radiation from frequent CT imaging has been implicated in the development of secondary malignancies, and contrast agents for CT and MRI can pose risks, particularly in patients with compromised renal function."