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Observational Study
. 2025 Mar;35(3):1205-1214.
doi: 10.1007/s00330-024-11150-3. Epub 2024 Oct 31.

The GREENWATER study: patients' green sensitivity and potential recovery of injected contrast agents

Moreno Zanardo  1 , Federico Ambrogi  2   3 , Luigi Asmundo  4 , Rosanna Cardani  5 , Giulia Cirillo  6 , Anna Colarieti  6 , Andrea Cozzi  6 , Massimo Cressoni  6 , Isabella Dambra  6 , Giovanni Di Leo  6 , Caterina B Monti  4 , Leonardo Nicotera  7 , Francesco Pomati  8 , Laura V Renna  5 , Francesco Secchi  6   9 , Marco Versuraro  5 , Paolo Vitali  6   9 , Francesco Sardanelli  6   9
Affiliations
Observational Study

The GREENWATER study: patients' green sensitivity and potential recovery of injected contrast agents

Moreno Zanardo et al. Eur Radiol. 2025 Mar.

Abstract

Objectives: The environmental footprint of iodinated contrast agents (ICAs) and gadolinium-based contrast agents (GBCAs) is noteworthy. This study assesses: (1) patients' "green sensitivity" as measured by their acceptance in a sustainability study and (2) the resulting potential reduction of contrast residuals in wastewater.

Materials and methods: After ethical approval, participants scheduled for administration of ICAs or GBCAs for diagnostic purposes were enrolled in this prospective observational study from July 2022 to October 2023. They were asked to prolong their hospital stay by up to 60 min to collect their first urine in dedicated canisters, thereby measuring the recovery rates of ICAs and GBCAs as found/theoretical ratio of concentrations. Mann-Whitney U, χ2 tests, and multivariable regression analysis were used.

Results: Patients scheduled for contrast-enhanced CT or MRI (n = 455) were screened; 422 (92.7%) accepted to participate. We enrolled 212 patients administered with ICAs and 210 administered with GBCAs. The median recovery rate was 51.2% (interquartile range 29.2-77.9%) for ICAs and 12.9% (9.0-19.3%) for GBCAs. At multivariable analysis, a significant effect of patient age (ICAs, p = 0.001; GBCAs, p = 0.014), urine volume (p < 0.001 for both), and time interval from contrast administration to urine collection (p < 0.001 for both) on recovery rates was found for both contrast agents; injected contrast volume (p = 0.046) and saline flushing usage (p = 0.008) showed a significant effect only for ICAs.

Conclusion: The high patient enrollment compliance (93%) and potential recovery rates of 51% (ICAs) and 13% (GBCAs) play in favor of sustainable practices in reducing the environmental footprint of contrast agents.

Key points: Question How many patients are willing to extend their stay in radiology by up to 60 min to help reduce the environmental impact of contrast agents? Findings Over 90% of screened patients agreed to extend their stay by up to 60 min and collect their urine in dedicated containers. Clinical relevance Patients demonstrated a high willingness to cooperate in reducing the environmental impact of contrast agents, allowing for a potential recovery of approximately 51% for iodinated and 13% for gadolinium-based contrast agents.

Keywords: Contrast media; Environmental fate; Gadolinium-based contrast agents; Iodinated contrast agents; Sustainability.

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Conflict of interest statement

Compliance with ethical standards. Guarantor: The scientific guarantor of this publication is F.S. Conflict of interest: The authors of this manuscript declare relationships with the following companies: F.S. has received research grants from Bracco, Bayer, GE. F.P. is an employee of ArsChemica S.R.L. The other authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article. Statistics and biometry: Professor Federico Ambrogi, Full Professor of Medical Statistcs at the University of Milan, kindly provided statistical advice for this manuscript. Informed consent: Written informed consent was obtained from all subjects enrolled in this study. Ethical approval: The GREENWATER study has been approved by the local Ethics committee (Comitato Etico Ospedale San Raffaele, then Comitato Etico Territoriale Lombardia 1, Milan, Italy; protocol number 53/INT/2022) on May 11, 2022, and emended on September 26, 2023. Study subjects or cohorts overlap: None. Methodology: Prospective Cross-sectional study/observational Performed at one institution

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