Fading hepatic hemangiomas on multiphasic CT.

PURPOSE: To describe fading hemangiomas [substantially lower attenuation (>30 HU) than vascular pool in the portal venous phase (PVP)] and to determine their incidence and characteristics on multiphasic CT. METHODS: The study population composed of 168 hemangiomas (≥5 mm) in 114 consecutive patients which were imaged on multiphasic CT and also proved by diagnostic findings on MRI. The size of hemangiomas and CT attenuation number of the enhancing area within the hemangioma, liver parenchyma, and portal vein were measured on both arterial phase (AP) and PVP images. The rapidity of enhancement (slow, <50%; rapid, 50%-99%; flash-filler, 100% filling in the AP) and association with arterioportal shunting (APS) were also determined by two independent reviewers. Imaging features were compared between fading and non-fading hemangiomas using Kruskal-Wallis test. RESULTS: Of 168 hemangiomas, the enhancing area of 27 hemangiomas (16%, 27/168) showed substantially lower attenuation than that of PV (fading) in the PVP. When the attenuation difference was compared with the rapidity of enhancement, flash-fillers showed lower attenuation than PV in the PVP more frequently than both slow-fillers (P < 0.05) and rapid-fillers (P < 0.05). The proportion of fading hemangiomas was 52% (14/27) in flash-fillers, much more frequent than in rapid-fillers (4/27, 15%) as well as slow-fillers (9/27, 33.3%). The size of fading hemangiomas (17.9 ± 4.5 mm) was significantly smaller than that of non-fading (24.2 ± 3.6 mm) (P = 0.032). Although APS was more frequent in fading hemangiomas (55.6%, 15/27) than that of non-fading hemangiomas (37.6%, 53/141), there was no statistically significant difference (P = 0.086). CONCLUSIONS: Sixteen percentage (27/168) of the hemangiomas in our study showed substantially lower attenuation than the portal vein in the PVP CT and this was more frequent in flash-fillers (52%, 14/27). The knowledge that fading does not preclude the diagnosis of hemangioma as well as of its high incidence in flash-fillers is important, as flash-filling hemangiomas with fading may cause a diagnostic challenge in patients suspected to have hypervascular malignancy.