Carbon dioxide-based portography: An alternative to conventional imaging with the use of iodinated contrast medium

Background and Aim: To clarify the efficacy of carbon dioxide (CO2) as a contrast material to evaluate portal vein images by percutaneous transhepatic portography (PTP). Methods: Twenty patients (38-76 years; male 13, female 7) with chronic liver diseases were the subjects of this prospective study. Portal venous opacification by PTP was compared between CO2-based images and iodinated contrast medium (ICM)-based images by two independent reviewers, according to the three-grade scoring; 0 for none, 1 for weak and 2 for sufficient. Results: Total scores of extrahepatic portal veins (137 for CO2, 93 for ICM), collateral vessels (64 for CO2, 60 for ICM) and intrahepatic portal veins (69 for CO2, 76 for ICM) were not statistically significant between CO2-based and ICM-based images (P = 0.0623). Sufficient opacification of superior mesenteric vein was more frequent on CO2-based images (none 0, weak 4, sufficient 16) than ICM-based images (none 19, weak 0, sufficient 1; P < 0.0001). The score was not statistically significant between CO2-based and ICM-based images in portal trunk, splenic vein, inferior mesenteric vein and other collateral vessels. Although opacification grade in the intrahepatic left portal vein was not statistically significant between CO2-based and ICM-based images (P = 0.1515), weak opacification was significantly frequent on CO2-based images (weak 10, sufficient 10) compared to ICM-based images (weak 0, sufficient 20; P = 0.0003) in the intrahepatic right portal vein. Inter-reviewer agreement was excellent between the two reviewers for CO2-based images (kappa = 0.913) and ICM-based images (kappa = 0.924). Conclusions: Carbon dioxide may be a first-line contrast material for evaluating portal vein images by PTP.