Hepatocellular carcinoma in cirrhotic liver: CT findings and the usefulness of delayed phase scan

Abstract

Background : Most hepatocellular carcinomas (HCCs) occur in an underlying cirrhotic liver. Some of which are difficult to diagnose because they do not show typical enhancement pattern, and cirrhotic nodules can mimic an HCC. Although multiphasic dynamic computed tomography (CT) has been used for detecting HCC, the usefulness of delayed phase scan is unclear.

Objectives : To analyze CT appearances of HCCs and other associated findings in cirrhotic livers, and to determine the usefulness of delayed phase scan for detecting HCCs.

Setting : Department of Radiology, Faculty of Medicine, Chulalongkorn University

Research design : Retrospective study

Materials and Methods : Fifty-three cirrhotic patients with 109 hepatic lesions underwent multiphasic dynamic CT scan. They were considered to have HCCs according to the Barcelona EASL 2000 HCC guideline and AASLD criteria. The combination of unenhanced, arterial and portal venous phase scans and the combination of unenhanced, arterial, portal venous and delayed phase scans of each patient was reviewed separately by two independent radiologists. Each lesion was evaluated regarding its size, focalization, location, attenuation, enhancement pattern and confidence level for diagnosing HCC.

Results : Most HCCs showed wash out of contrast material on portal venous phase scan (64.2 -66%). Approximately, one-fourth of HCCs showed wash out on delayed phase scan, higher percentage in small HCCs with a diameter of less than 2 cm (31.6 - 42.1%) compared to those with a diameter of more than 2 cm (23.4 - 24.5%). On delayed phase scan, 40.4% of HCCs showed capsular enhancement. There were tumor involvement of portal veins and hepatic veins in 17 patients (32.1%) and one patient (1.9%), respectively. Arterioportal shunt was present in 5 patients (9.4%) and bile duct dilatation was found in 3 patients (5.7%). Mean confidence level for diagnosing HCC by combined unenhanced, arterial and portal venous phase scans was 4.28-4.45 and 4.63 for combined unenhanced, arterial, portal venous and delayed phase scans. The confidence level increased significantly after adding the delayed phase scan (P<.05).

Conclusion : CT findings on delayed phase scan are helpful in the diagnosis of HCC, especially in small HCCs with a diameter of less than 2 cm. Adding the delayed phase scan shows significantly increased confidence level and can confirm the diagnosis.