OTTAWA (CP) - Health Canada has notified Canadian hospitals about safety concerns over certain contrast agents used in diagnostic imaging that have been linked to a rare and potentially fatal skin disease.

A contrast agent is a liquid injected into the body to make certain tissues more visible during imaging procedures. Contrast agents containing gadolinium - which are used primarily in magnetic resonance imaging (MRI) - have been linked to a condition called nephrogenic systemic fibrosis/nephrogenic fibrosing dermopathy, or NSF/NFD.

To date, 109 cases of NSF/NFD associated with gadolinium-containing contrast agents have been reported worldwide, although none has been reported in Canada. So far, NSF/NFD has been observed only in patients with serious kidney disease, Health Canada said Tuesday in an advisory.

NSF/NFD may develop over a period of a few days to several weeks, with lesions on the skin the most visible effect. The skin becomes thickened with a woody texture, restricting joint movement and resulting in the shortening or distortion of muscle tissue.

"Internal organs such as the heart may also be affected," Health Canada said. "A skin biopsy is necessary to accurately diagnose this disease."

The seven gadolinium-containing contrast agents authorized for sale in Canada are Omniscan, Magnevist, Optimark, Gadovist, ProHance, MultiHance and Vasovist.

The federal department recommends that patients with serious kidney disease consult their health-care professionals to minimize the risk of developing NSF/NFD following an imaging procedure.

Consumers requiring more information can contact Health Canada's public inquiries line at 613-957-2991, or toll free at 1-866-225-0709.