Arterioportal shunt: prevalence in small hemangiomas versus that in hepatocellular carcinomas 3 cm or smaller at two-phase helical CT.

Purpose: To compare the prevalence of arterioportal (AP) shunting associated with (a) small (< or =3 cm) hemangiomas and (b) hepatocellular carcinomas (HCCs) (< or =3 cm) at two-phase helical computed tomography (CT).
Materials and Methods: Two-phase helical liver CT was performed in 107 patients (61 men, 46 women; age range, 25-73 years; mean, 48.6 years) with 169 small hemangiomas and in 384 patients (292 men, 92 women; age range, 18-82 years; mean, 58.3 years) with 598 HCCs 3 cm or smaller. Diagnosis of HCC was verified with histologic findings (n = 30) or typical imaging and clinical findings (n = 568); that of all hemangiomas was verified with typical imaging and clinical findings. Three radiologists retrospectively reviewed all CT images in consensus. Contrast material-enhanced CT scans were obtained during the hepatic arterial and portal venous phases. AP shunt was considered to be present when wedge-shaped or irregularly shaped homogeneous enhancement peripheral to tumor appeared at hepatic arterial phase CT and isoattenuation or slight hyperattenuation in that area appeared at portal phase CT. The prevalence of AP shunting associated with hemangiomas and that associated with HCCs were compared with multivariate model testing. Speed of lesion enhancement (rapid enhancement, when extent of intratumoral enhancement at hepatic arterial phase CT was >50%; slow enhancement, when extent of intratumoral enhancement was < or =50%) and presence of AP shunt were correlated with chi2 or Fisher exact testing.
Results: AP shunts were more frequently found in hemangiomas (36 lesions [21.3%]) than in HCCs (25 lesions [4.2%]) (P <.001). Twenty-four (38%) of the 64 hemangiomas with rapid enhancement had AP shunts, whereas only 12 (11.4%) of the 105 hemangiomas with slow enhancement had AP shunts (P <.001). There was no significant difference between prevalence of AP shunt in the 573 HCCs with rapid enhancement (24 lesions, 4.2%) and that in the 25 HCCs with slow enhancement (one lesion, 4.0%).
Conclusion: AP shunts were more frequently seen at two-phase helical CT in small hepatic hemangiomas than in HCCs and thus represent a suggestive but not specific finding of hemangioma. Small hemangiomas with AP shunts tend to show rapid rather than slow enhancement.
(Copyright RSNA, 2004)