Greener Choices in Biliary Imaging: A Prospective Carbon Footprint Comparison of EUS versus MRCP for Intermediate-Likelihood Choledocholithiasis.

INTRODUCTION: Healthcare accounts for nearly 5% of global greenhouse gas (GHG) emissions, and medical imaging is among its most energy-intensive activities. For intermediate-likelihood common bile duct (CBD) stones, endoscopic ultrasound (EUS) and magnetic resonance cholangiopancreatography (MRCP) are both guideline-endorsed with comparable diagnostic accuracy, yet their environmental costs have never been directly compared. METHODS: In this prospective study, we measured the per-procedure carbon footprint of EUS and MRCP using the Greenhouse Gas Protocol and India's grid emission factor. We recorded EUS procedure times individually; MRCP emissions were derived from a validated power model that captures the continuous cryocooler load maintaining magnet superconductivity around the clock, with shared infrastructure allocated by real case volume. We performed sensitivity analyses across scanner utilization, energy-allocation method, scan duration, and grid carbon intensity. The study followed the ESGE E-SPARE reporting standard. RESULTS: EUS generated 4.53 kg CO2e per procedure and MRCP 18.90 kg CO2e per procedure, making MRCP 4.2 times more carbon-intensive. The continuously running cryocooler was the single largest fixed contributor to MRCP emissions (23.4% in standby alone), a 24/7 load absent in EUS. Choosing EUS for 108 patients saved 1,552 kg CO2e, equivalent to the annual carbon uptake of 74 mature trees. EUS remained the lower-carbon option across sensitivity analyses, though the advantage narrowed and could reverse on low-carbon grids. DISCUSSION: For bile duct stone evaluation, EUS offers the same diagnostic answer at substantially lower carbon cost where grid electricity is carbon-intensive, adding environmental impact to accuracy, safety, and cost in the decision.