Extrahepatic collateral arteries commonly supply hepatocellular carcinomas if the tumors are large or peripherally located. Because development of these vessels interferes with effective control of the tumor with transcatheter arterial chemoembolization (TACE), radiologists should become familiar with the imaging findings of extrahepatic collateral vessels to detect them at an early stage. The authors observed 2104 such vessels in 860 patients over 5.5 years. The extrahepatic collateral vessels observed originated from the inferior phrenic artery, omental branch, adrenal artery, intercostal artery, cystic artery, internal mammary artery, renal or renal capsular artery, branch of the superior mesenteric artery, gastric artery, and lumbar artery. The authors suspected extrahepatic collateral vessels when (a) a tumor grew exophytically or invaded adjacent organs, (b) a tumor was in contact with the ligaments and bare area of the liver, (c) a hypertrophied extrahepatic collateral vessel was observed on a computed tomographic (CT) scan, (d) a peripheral defect of iodized oil retention within a tumor was seen during chemoembolization or on a follow-up CTscan, (e) a local recurrence developed at the peripheral portion of the treated tumor during follow-up, or (f) a sustained elevation in serum alpha-fetoprotein level was noted despite adequate embolization of the hepatic artery. When both the hepatic artery and extrahepatic collateral vessels supply a tumor, additional extrahepatic collateral vessel chemoembolization should be attempted to increase the therapeutic efficacy of TACE for hepatocellular carcinoma.
