Doctors sometimes give patients a medicine called gadolinium during an MRI scan to help make the pictures clearer. However, scientists at the University of New Mexico have found that small pieces of gadolinium can go into people’s kidneys and cause serious side effects. In some cases, the metal can cause a disease called nephrogenic systemic fibrosis, which is very painful and sometimes deadly.

The scientists used a unique tool called electron microscopy to see tiny bits of gadolinium in the kidneys of people who had gotten contrast agents before their MRI. The contrast agent is a substance that contains gadolinium, and it helps the MRI show more detail.

Although gadolinium helps make the pictures clearer, it can also be dangerous. The metal needs to be attached to particular molecules so the body can filter it out and get rid of it. However, scientists found that some gadolinium particles can break free and go into the kidneys and other parts of the body.

About half of all MRI scans use contrast agents with gadolinium, but not everyone who gets the substance has adverse side effects. It is unclear why some people get sick and others don’t. The risk of developing side effects increases the more a person is exposed to the contrast agent.

Scientists are worried that many doctors may not know about the risks of using gadolinium-based contrast agents. They think the substance is given too often, even when people don’t need it.

Another problem is that gadolinium can get into the environment. After people get an MRI with gadolinium, the substance comes out of their body in their urine. But wastewater treatment plants cannot remove the metal, so it can end up in rivers, lakes, and oceans. Gadolinium has even been found in tap water in some places.

Scientists still have many questions about gadolinium and how it affects the body. They are continuing to study the metal and try to figure out how to make MRI scans safer for everyone.