Carbon Dioxide Pyelography: A Convenient and Safe Alternative to Both Room Air and Iodinated Contrast Pyelography...

Introduction/Background: There are increasing reports of serious complications related to the air pyelography technique, which raise concerns about the safety of room air (RA) injection into the renal collecting system. Carbon dioxide (CO₂) is much more soluble in blood than nitrogen and oxygen and thus considerably less likely to cause gas emboli. Iodinated contrast medium (ICM) is expensive, and supplies may not be as reliable as previously assumed. CO₂ pyelography (CO₂-P) techniques using standard fluoroscopy and digital subtraction fluoroscopy (CO₂ digital subtraction pyelography [CO₂-DSP]) are described. Materials and Methods: During the endourologic stone cases, 15 to 20 mL of CO₂ gas was typically injected into the renal pelvis through a catheter or sheath. Imaging was usually obtained with endovascular CO₂ digital subtraction angiography settings using either a traditional fluoroscopy system (TFS) or robotic arm multiplanar fluoroscopy system (RMPFS) (Artis Zeego Care+Clear^®; Siemens). Results: CO₂-P was performed in 22 endoscopic stone treatment cases between March 2021 and August 2022, primarily using digital subtraction settings in 20 cases. CO₂-DSP overall provided higher quality images of the renal pelvis and collecting system than CO₂-P, but with a relatively higher radiation dose. Following a quality intervention, fluoroscopy doses for CO₂-DSP cases were decreased by 81% overall. The use of CO₂-P avoided fluoroscopic or intraoperative CT (ICT) artifacts seen with intraluminal ICM. Conclusions: CO₂-P allows the urologist to obtain imaging of the renal collecting system without ICM and with much lower risk of air embolism compared with RA pyelography. CO₂ is a nearly cost-free alternative to ICM. Because CO₂ is widely available and the technique is easy to perform, we propose that CO₂-P should be favored over traditional air pyelography to improve patient safety.