Kinetics of Urinary Excretion of Gadolinium Contrast Agents Used in MRI Examinations

The contrast agents used in MRI to characterize certain lesions contain a chemical element from the rare earth family: Gadolinium (Gd). Gd, in its isolated form, is toxic in humans, but it can still be used in the form of complex molecules such as gadolinium contrast agents (Gd-CAs), which retain its contrast power while greatly minimizing its toxicity.

The MRI is performed rapidly after the injection of Gd-CAs, and these compounds are eliminated by the urinary route in the first urine following the examination. After elimination, and in view of their very high stability, these compounds follow the path of wastewater via sewage treatment plants. However, the processes currently used in these plants do not retain them, and they remain present in the purified water discharged into rivers.

Work carried out at the Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC) at the University of Lorraine has demonstrated the bioaccumulation of these compounds in freshwater organisms. Gd-CAs then follow the classic pathway of continental waters. It should be noted that the quantity of Gd released as a result of MRI activities has been estimated on average at 1 injection per 1 g of Gd used.

In order to prevent future environmental disorders, recovery of all or part of the Gd-CAs immediately after MRI by urine collection is undoubtedly the most effective approach.

The aim of this project is to assess the feasibility of such an approach, and to propose a protocol applicable to MRI involving the injection of gadolinium contrast agents for urine collection.

This project is part of the "Rare Earths" theme of LabEx R21. It will examine the possibility of recycling gadolinium as an element or as Gd-CAs.

Inclusion criteria

Patients:

• over 18 years of age
• with a prescription for MRI with gadolinium-based contrast agents (Gd-CAs) injection validated by a radiologist
• affiliated with a health insurance plan
• have signed an informed consent form

Exclusion criteria

• Patients:
• with known allergy to gadolinium-based contrast agents (Gd-CAs)
• with known severe renal impairment (GFR < 30 mL/min)
• on dialysis
• with urinary incontinence
• with an ongoing urinary tract infection
• under hydric or hydrosodic restriction
• unable to urinate independently
• Protected persons (under guardianship, curatorship or safeguard of justice)
• Pregnant or breast-feeding women