Gadolinium Retention Estimation Tool

Spot urine or chelate-provoked urine gadolinium concentrations are often measured in patients with complaints following Gd-CM administration. However, interpreting these results can be challenging, as gadolinium excretion depends on the toxicokinetics of the specific contrast agent, which is renally cleared over an extended period and partly stored long-term in the body. There is some confusion among physicians about normal ranges of gadolinium concentrations in spot and chelate-enhanced urine samples, particularly in relation to the time elapsed since Gd-CM exposure.The estimator in this Excel file provides a tool for estimating individual gadolinium retention and excretion capacity based on the time-lapse (in months) between the administration of Gd-CM and urine sample collection. Users can input spot urine and Chelate-Evoked Metal Excretion Test (CEMET) urine concentrations in µg/g creatinine. These values are then aggregated into norm-regression curves with ±95% Confidence Intervals (CI). The norm curves are based on data from 54 patient samples. Spot urine samples were collected from patients in the morning while fasting. Following this, a standard intravenous infusion of 600 mg glutathione, 1.9 g Na-Ca-EDTA, and 250 mg DMPS was administered, with CEMET urine collected two hours after infusion. This combination of metal excretion agents was designed to enhance sensitivity and broaden the spectrum of metals captured by the Chelate-Evoked Metal Excretion Test (CEMET). Notably, Na-Ca-EDTA is effective at binding and promoting the urinary excretion of gadolinium and can be used as an alternative to Zn-DTPA for this purpose. The tool generates two separate regression curves: one for short- to medium-term gadolinium retention (<24 months, located in Sheet 1) and another for long-term retention (2–10 years, located in Sheet 2), as the slopes of the norm curves differed between these periods.Sheet 3 provides a Python script for generating norm diagrams and aggregating patient data. This script can be adapted to specific patient subsets, such as those distinguished by renal function, lifetime gadolinium exposure, or specific Gd-CM types or brands. While the tool helps estimate the degree of gadolinium retention in tissues after defined intervals following Gd-CM administration, it should be noted that elevated gadolinium retention values do not necessarily correlate with symptoms. Some patients with typical retention values may exhibit symptoms, while patients with elevated retention may remain asymptomatic.Increased sensitivity to gadolinium and related pathology appears to involve autoimmune mechanisms or predisposing factors, such as decreased metal tolerance and increased pre-exam metal exposure, which are not directly correlated with gadolinium concentrations in blood. Thus, this tool is valuable for estimating individual gadolinium retention after exposure to Gd-CM, but it is not intended to determine toxicity levels.