Gadolinium-based contrast agents (GBCA) are widely used in magnetic resonance imaging (MRI) to improve image quality, particularly in angiography and oncologic imaging.1 Gadolinium (Gd) is a naturally occurring heavy metal. In its elemental form, gadolinium is toxic, but, when bound to chelating agents, it is safe for use in humans. GBCA are usually injected intravenously at the start of the MR scan. The extent of gadolinium use in imaging is ubiquitous. In 2018, it was estimated that, since approval in 1988, over 460 million dosages of gadolinium had been administered worldwide.2
Acute allergic reactions to gadolinium are rare. Nephrogenic systemic fibrosis (NSF), a systemic disorder linked to GBCA administration in patients with impaired renal function,3 has decreased in incidence with the use of newer GBCAs and a more cautious approach to administration.
The phenomenon of gadolinium deposition in the brain was first described in 2014 on MRI images.4 Subsequent studies have confirmed that these signal changes in the brain correspond to gadolinium deposition; this phenomenon occurs in patients with normal renal function. There is no definite evidence linking gadolinium deposition in the brain with any adverse patient outcome.
Despite the lack of causation of a disease state, the action of regulators in the US and Europe has been remarkable. In the US, the Food and Drug Administration took the step of requiring imaging centres to distribute patient Medication Guides to better apprise patients of GBCA-associated risks before administration. The European Medicines Agency went further by restricting the use of certain GBCAs, while concluding that ‘there is currently no evidence that gadolinium deposition in the brain has caused any harm to patients’.5
We raise this clinical and regulatory conundrum for the information of colleagues in primary care as, with more direct requesting of a wider range of imaging investigations by GPs, it is likely that questions on this topic will be posed by patients. Colleagues in primary care would be advised to seek up-to-date advice from the radiology department of their local hospital or imaging services provider, as the regulatory position on this topic will undoubtedly alter as new evidence emerges.
- © British Journal of General Practice 2021
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