A simple hepatic cyst is a single, unilocular lesion containing homogeneous serous fluid surrounded by a single layer of cuboidal epithelium, identical to that of bile ducts, and a thin underlying layer of fibrous stroma [1].

Usually, a correct diagnosis is already allowed by means of grayscale US thanks to a homogeneous anechoic appearance, a thin or imperceptible wall with posterior acoustic enhancement. Some internal thin septa may be present, but thick septa should suggest an abscess, parasitic infection, or cystic neoplasm. In particular, at CEUS, cystic tumors of biliary origin and cystic metastasis usually present a thick capsule, thick internal septa, or mural nodules which show contrast enhancement suggesting the presence of viable tissue [2].

Furthermore, hemorrhagic or complicated cysts may show hypoechoic inhomogeneous appearance instead of typical anechoic aspect on conventional US scan. In these cases, CEUS can depict the absence of vascularization throughout the vascular phase, suggesting cystic nature.

Hydatid disease is a parasitic infestation by a tapeworm of the genus Echinococcus.

Cystic hydatid disease usually affects the liver (50–70 %) and less frequently the lung, the spleen, the kidney, the bones, and the brain. Liver hydatidosis can cause dissemination or anaphylaxis after a cyst ruptures into the peritoneum or biliary tract. Infection of the cyst can facilitate the development of liver abscesses and mechanic local complications, such as mass effect on bile ducts and vessels that can induce cholestasis, portal hypertension, and Budd-Chiari syndrome. At baseline US, hydatid cysts may present a solid aspect because of its inhomogeneous complex appearance. Parasitic cyst usually presents as a single, unilocular cyst or multiseptated cysts, showing “wheel-like,” “rosette-like,” or “honeycomb-like” appearances. “Snowstorm” sign may appear as multiple internal echogenic foci within the cyst cavity (hydatid sand). A correct diagnosis is of clinical relevance since biopsy of these lesions is not recommended in order to avoid severe adverse events. Usually, CEUS shows lack of enhancement of septa separating daughter cysts [3, 4].

Hemangioma is the most frequent primary benign tumor of the liver found out with a prevalence range varying from 1 to 20 % and a higher incidence in females (women/men: 2/1–5/1).

At histopathological analysis, hemangioma is characterized by vascular lacunae lined by a single layer of endothelial cells associated with a variable rate of fibrous tissue [5, 6]. The differential diagnosis with other hepatic lesions has a pivotal clinical impact since it does not require any treatment.

At grayscale US, the hemangioma can present a “typical” aspect—hyperechoic lesion, variable in size with homogeneous or slightly inhomogeneous echotexture, well-defined margins with or without posterior wall shadowing—making easy a correct diagnosis especially in patients with no history of malignancy or chronic liver disease. Usually, color- and power-Doppler evaluation does not show any vascular signal within or at the periphery of the lesion because of very slow blood flows that distinguish it. Except for patients with cancer history or known chronic HBV-HCV-related liver disease, the detection of a lesion presenting these imaging findings does not require any further investigation.

Nevertheless, on grayscale US, hemangioma may show atypical features, such as an inhomogeneous internal echotexture. In particular, hemangiomas larger than 4–5 cm may present a markedly inhomogeneous aspect, because of thrombohemorrhagic episodes, cystic degeneration, fibrosis or hyalinization, and calcium deposit [7]. In these latter cases, CEUS represents a useful tool in order to more precisely characterize the lesion demonstrating, as shown at contrast-enhanced CT and MR, peculiar and specific contrast enhancement patterns [8–10]. In fact, CEUS allows the depiction of typical peripheral nodular enhancement in the arterial phase followed by a progressive centripetal fill-in in the extended portal-venous phase, which is considered diagnostic for hemangioma on contrast-enhanced CT and MR [11]. Incomplete fill-in in the extended portal-venous phase can depend either on the lesion size and the presence of thrombohemorrhagic phenomena or fibrosis [12]. In a smaller percentage of cases, it is possible to observe a peripheral rim enhancement in the arterial phase followed by a progressive centripetal complete or incomplete fill-in [13]. And finally, lesions smaller than 2 cm can show a rapid and homogeneous uptake of contrast medium in the arterial phase with sustained contrast enhancement in the remaining phases [14]. This feature is suggestive of capillary hemangioma. Capillary hemangioma could cause misinterpretation since other benign (focal nodular hyperplasia, hepatocellular adenoma) and malignant lesions (well-differentiated hepatocellular carcinoma) present this contrast enhancement behavior. Hence, clinical history is of pivotal relevance since if a lesion presenting these findings at CEUS is found out in a patient with chronic hepatitis, further investigations such as MR with hepatocellular-specific contrast medium are needed in order to rule out a well-differentiated hepatocellular carcinoma or a dysplastic nodule [15, 16].