Proximal arterioportal shunt in hepatocellular carcinoma: multi-slice spiral CT features and its clinical significance

Objective To evaluate the dynamic enhanced multi-slice spiral CT features and the formative mechanisms of proximal arterioportal shunt (APS) associated with hepatocellular carcinoma (HCC), and to assess the CT diagnostic ability and clinical value for proximal APS by comparing with digital subtraction angiography (DSA). Methods One hundred and sixty-eight patients with HCC received both dynamic enhanced multi-slice spiral CT scan and DSA of the liver, and the time lapse between these two examinations was from 3 to 15 days. Of the 168 patients, 37 were massive tumors, 102 were nodular, and 29 were diffuse, respectively. Spiral CT signs and its diagnostic ability for proximal APS were analyzed and compared with the golden standard of DSA. Peripheral hepatic segmental or subsegmental small APS were excluded in our study. Results Of the 168 patients with HCC, 42 (25.0%) were demonstrated to have proximal APS on DSA, and all the of 42 patients had positive CT findings related to proximal APS in arterial phase. Of the 6 patients proved to have false positive CT signs, 2 showed lower enhancement of portal vein (PV) than that of the aorta. The sensitivity, specificity, accuracy, and positive and negative predictive value of spiral CT in diagnosing proximal APS were 100.0%, 95.2%, 96.4%, 87.5%, and 100.0%, respectively. There was a good correlation on the extent of APS to main PV, left or right PV, superior mesenteric vein, splenic vein, and coronary vein between CT and DSA in 35 patients (83.3%). The extent of APS to main PV and left or right PV was well correlated between CT and DSA in 38 patients (90.5%). The direct CT signs of proximal APS in arterial phase were revealed as early and strong enhancement of main PV and/or left or right PV approaching the density of the aorta (n=38). The indirect CT signs of proximal APS in arterial phase were demonstrated as high attenuation of normal hepatic parenchyma in the lobar distribution ipsilateral to the tumor (n=4). Conclusion The dynamic enhanced multi-slice spiral CT can be used as an important tool for the diagnosis of proximal APS associated with HCC, and its diagnostic accuracy could be comparable to that of DSA. The transvascular route is the main formative mechanism of proximal APS in HCC. CT diagnosis of proximal APS is of important clinical significance in the treatment of HCC.