MRI contrast agents may cause gadolinium toxicity symptoms, prompting the FDA to call for further investigation and research.

Gadolinium contrast agents, often referred to as “contrast” or “dyes”, are used during MRI scans to enhance the imaging capabilities of the test. According to Inside Radiology, these contrast agents are used in about 1 in 3 MRI scans.

The contrast agents are given through the an IV typically during an MRI scan. By using these gadolinium contrasts, radiologists are able to get better visibility of inflammation, tumors, blood vessels and tissues. This can be extremely important when diagnosing various conditions through an MRI scan.

Typically, 90 percent of gadolinium contrast is processed out through urine within the 24 hours of injection. However, these agents may cause gadolinium toxicity symptoms if the heavy metal is retained in the skin, bone, brain and other organs.

In late 2017, the U.S. Food and Drug Administration (FDA) called for the addition of strict warnings on gadolinium contrast agents. The agency also called for “additional research” into gadolinium toxicity symptoms and how much gadolinium is retained in the body after use of contrast agents.

Dr. Janet Woodcock, who serves as director of the FDA’s Center for Drug Evaluation and Research, stated that gadolinium contrast agents may not be recommended “for patients who may be at higher risk, such as those who may require repeat GBCA MRI scans to monitor a chronic condition,” according to HealthDay.

The FDA noted that “gadolinium retention has not been directly linked to adverse health effects” for most patients and that “the benefit of all approved GBCAs continues to outweigh any potential risks.”

Currently, gadolinium contrast agents are not recommended for use in patients with kidney failure. In this group, gadolinium agents have reportedly been linked with a painful thickening of the skin.

Some researchers reject the idea that gadolinium retention can cause serious, long term health effects. Before the FDA’s announcement in late 2017, researchers from the Mayo Clinic conducted a study of 4,300 adults which reportedly found no evidence that exposure to gadolinium contrast agents were associated with mental decline.

“This study provides useful data that at the reasonable doses 95 percent of the population is likely to receive in their lifetime, there is no evidence at this point that gadolinium retention in the brain is associated with adverse clinical outcomes,” said lead researcher Dr. Robert McDonald during a news release, HealthDay reports.

Scientists such as Dr. Vikas Gulani reportedly remain flexible about the safety profile of gadolinium agents due to the vast number of unknowns. The agents have been in use for decades, but research is only now being done about the side effects of gadolinium retention and toxicity.

Gulani, who serves as an associate professor of radiology at Case Western Reserve University, notes that even the Mayo Clinic study doesn’t rule out the potential for neurological side effects and other adverse outcomes.

Luckily, gadolinium contrast is not necessary in every MRI scan.

“It’s just like with any other medication,” Gulani said. “If you don’t need it, don’t use it.”