GREENWATER 2.0: Reducing Iodinated Contrast Agents in Hospital Wastewater

GREENWATER 2.0 is a single-center, prospective observational study with an additional urine collection procedure. The study will be conducted in the diagnostic imaging department of IRCCS Ospedale Galeazzi - Sant'Ambrogio and will include adult outpatients undergoing clinically indicated contrast-enhanced CT scans with iodinated contrast agents.

Iodinated contrast agents are widely used in CT imaging to improve diagnostic accuracy. After intravenous administration, these agents are predominantly eliminated unchanged through urine. Because conventional wastewater treatment may not fully remove iodinated contrast agent residues, urine collection shortly after contrast administration may represent a practical strategy to reduce their release into hospital wastewater.

The study builds on the previous GREENWATER study, which showed high patient willingness to participate in a sustainability-focused urine collection protocol after contrast-enhanced imaging. In GREENWATER 2.0, a dedicated urine collection device will be installed in the radiology department to make the collection process more practical and integrated into the clinical workflow.

Participants will undergo their scheduled CT scan according to standard clinical practice. The indication for the CT scan, the choice of iodinated contrast agent, the contrast dose, and the imaging protocol will not be modified for research purposes. After contrast injection, participants will be asked to remain in the radiology department for about 60 minutes and then use the dedicated urine collection device before leaving the hospital.

The study will evaluate whether this workflow is acceptable and feasible for patients in routine radiology practice. It will also assess the potential recovery of iodinated contrast agent residues from the collected urine. Additional information will be collected on the contrast agent administered, the volume of urine collected, the time between CT examination and device use, and patient-reported experience with the device, including comfort, ease of use, cleanliness, privacy, odor, waiting time perception, and clarity of instructions.

The study is expected to provide evidence on the feasibility of using a dedicated urine collection device in a hospital radiology department as a sustainability measure to reduce the environmental impact of iodinated contrast agents. The planned sample size is 416 participants, with recruitment expected to last approximately 12 months. The total study duration is expected to be approximately 18 months, including recruitment, data analysis, and preparation of the final study report.

Inclusion criteria

• Adult patients aged 18 years or older.
• Patients scheduled for a clinically indicated contrast-enhanced CT scan with iodinated contrast agent.
• Patients able to provide written informed consent.
• Patients willing to wait approximately 60 minutes after contrast injection before using the dedicated urine collection device.

Exclusion criteria

• Patients unable to use the dedicated urine collection device for urine collection.