Inferior phrenic arteries: angiographic anatomy, variations, and catheterization techniques for transcatheter arterial chemoembolization.

The inferior phrenic artery (IPA) is the most common extrahepatic collateral vessel to hepatocellular carcinoma (HCC); however, there are many anatomical variations in its origin and branches. In addition, the IPA is frequently reconstructed through several pathways, mainly through the retroperitoneal network, because of the occlusion of its orifice due to atherosclerosis or previous catheter manipulation. Infrequently, selective catheterization into the IPA is impossible even using a microcatheter, particularly in the IPA that originates from the proximal or distal portion of the celiac trunk or from the aorta with an acute angle. In this article, we describe anatomical variations of the IPA and catheterization techniques, such as a catheter with a large side hole and a catheter with a cleft, to facilitate catheterization into the IPA that is difficult using a conventional coaxial technique. Radiologists should have sufficient knowledge of such variations and catheterization techniques to perform transcatheter arterial chemoembolization for HCCs through the IPA effectively and safely.