CT Findings in Liver Cancer, October 31, 1996

CT Findings in Liver Cancer, October 31, 1996

CT scans do not require fasting, but intestinal gas is a major contraindication; therefore, avoid consuming coarse, fibrous foods before the exam to prevent excessive gas production. Liver and kidney function should be assessed beforehand, or an iodine allergy test performed, since contrast-enhanced scans are conducted after intravenous injection of iodine-containing contrast agents. Contrast-enhanced scans improve the diagnosis of liver cancer and are particularly useful in differentiating it from cavernous hemangiomas. Non-contrast scans are called plain scans; clinically, it is extremely difficult to distinguish between cavernous hemangiomas and liver cancer on plain scans, but contrast-enhanced scans provide much clearer differentiation. Patients with hyperthyroidism, heart failure, liver failure, or kidney failure should not undergo contrast-enhanced scans—please remember this. Direct CT signs of liver cancer include localized areas of decreased density with relatively well-defined borders, which may appear singly or in multiples, sometimes with blurred or indistinct margins. Occasionally, tumor tissue necrosis results in uneven low-density shadows, and during contrast-enhanced scans, high-density septa appear within the lesion, varying in width and orientation—some refer to this as the “septal sign.” Generally speaking, abnormal liver shape and displacement of the porta hepatis can be observed. The porta hepatis is located between the left and right lobes, as well as the quadrate and caudate lobes; any large liver cancer in any lobe can cause displacement of the porta hepatis. Additionally, portal vein tumor thrombus is a common manifestation of liver cancer, where the vessel thickens and enlarges, and contrast-enhanced scans show filling defects within the lumen, accompanied by signs of cirrhosis, irregular liver contour, hepatomegaly, ascites, widened interlobar fissures, and proliferation of the caudate lobe.