Hemangiomas are large, thin-walled, blood-filled vascular spaces lined by epithelium and separated by fibrous septa. They are the most common benign liver tumor (78%) and are the second most common liver lesion overall, behind metastatic disease.

The incidence is approximately 1-4%. They are rarely seen in young children and when present, are predominantly in females (M:F 1:4).

Typically they are asymptomatic, but larger lesions may present with hemorrhage, abdominal discomfort, or pain (when thrombosed). They frequently enlarge during pregnancy and are more common in multiparous women. Hemangiomas may present with spontaneous life-threatening hemorrhage if large (5% of lesions). Over 90% are less than 4 cm.

Radiologic hallmarks of hemangiomas are as follows:
US: VARIABLE, from uniformly hyperechoic (60%) due to multiple interfaces created by blood-filled spaces separated by fibrous septa to inhomogenous hypoechoic (up to 40%) in larger hemangiomas with well-defined thick or thin echogenic lobulated borders due to hemorrhagic necrosis and scarring. They typically have no Doppler signal to ones with peak velocity less than 50cm/sec.

CT (precontrast, and dynamic scanning post-contrast):
1. Well-defined hypodense mass of same density as other blood-filled spaces (portal vein) on unenhanced images.
2. Develop nodular like areas of enhancement in periphery after rapid bolus contrast medium.
3. Areas of enhancement become confluent with entire lesion gradually becoming iso- to hyper-dense relative to liver parenchyma.
4. Enhancement persists in lesion for 20-30 minutes after injection.
5. Large lesions can present with discrete areas of fibrosis and occasionally calcification that are hypodense throughout the entire period of enhancement.
When these findings are observed, CT is diagnostic with high degree of confidence. If questions persist, tagged red blood cell scintigraphy is usually diagnostic.