Urinary Gadolinium Levels After Contrast-Enhanced MRI in Individuals with Normal Renal Function: a Pilot Study.

Introduction: Gadolinium-based contrast agents (GBCA) have been used to enhance magnetic resonance imaging (MRI) since 1985. Recently, the media and online groups have voiced concerns about gadolinium deposition in patients with normal renal function based on "elevated" urinary gadolinium levels. The determination of increased urinary gadolinium levels is based on reference ranges developed in individuals with normal renal function who were never exposed to GBCA. Studies suggest an elevated gadolinium urinary elimination greater than 72 h post GBCA scan. We evaluated urine gadolinium concentrations over a 30-day period in patients administered GBCA.

Methods: In this prospective, observational pilot study, we enrolled subjects between 18 and 65 years of age with normal renal function who received GBCA for the first time. Urinary gadolinium was measured at days zero (prior to GBCA exposure), 3, 10, and 30 after GBCA exposure. We compared urinary gadolinium levels after GBCA exposure to the current reference range and calculated an estimated duration of "elevated" gadolinium urine levels in the average patient.

Results: All 13 subjects had 24-h urinary gadolinium levels higher than 0.7 μg/24 h with means of 1944 (± 1432) μg/24 h on day 3, 301 (± 218) μg/24 h on day 10, and 34 (± 33) μg/24 h on day 30. Based on calculated urinary gadolinium elimination kinetics, we estimate urinary gadolinium levels will often remain above the current reference range for > 50 days.

Conclusion: The current reference range of 0.7 μg/24 h for 24 h urinary gadolinium is not applicable to patients for at least 30 days following GBCA exposure.