Anechoic Masses

wall since, although the cysts are lined by a simple columnar epithelium, they do not exhibit any wall structures. Complications may arise from hemorrhage into or infection of the cysts; apart from the clinical sign of local tenderness it may alter/increase the echogenicity of the pathological cystic contents.

Hemorrhage/Hematoma

Hemorrhage or localized hematoma (Fig. 2.63, 2.8 p–r) may be due to local trauma, e. g., needle biopsy, stab wound, or rupture of healthy adjacent tissue, and is different from bleeding into an existing lesion (e. g., adenoma, metastasis). Typically, a recent hematoma is anechoic and exhibits a smooth boundary with the surrounding tissue; in cases of major parenchymal rupture, the shape could become irregular and even bizarre. Subcapsular hemorrhage may lift the capsule off the liver like a tent. The bleeding is characterized by a less than optimal posterior enhancement, and frequently the adjacent parenchyma displays a slight increase in echodensity due to compression artifacts. Older hemorrhages/hematomas

Fig. 2.62 Polycystic liver disease. Finding during laparoscopy.

Fig. 2.63 Subcapsular hematoma in the posterior face of the left hepatic lobe; guided-needle biopsy under sonography.

lose their anechogenicity: the bleeding becomes organized, first with hypoechoic and later with hyperechoic intraluminal thrombi, which may appear in bizarre lumps and strands.

Hemorrhage/Hematoma

Hemorrhage. Bleeding in the liver may be due to inadvertent trauma, iatrogenic injury (needle biopsy, drainage), or coagulation disorder, or it may complicate a preexisting mass (e. g., adenoma). The typical finding is a hypoechoic to anechoic liquid mass; in rare cases (due to compression) it is homogeneously hyperechoic. The mass caused by a hemorrhage is sharply delimited and sometimes irregular in shape; the surrounding tissue is compressed (increased echogenicity), and quite often the patient is in pain (capsular tension).

Older hemorrhage. Apart from irregular liquid regions, these demonstrate inhomogeneous echogenic areas corresponding to clots, strands of fibrin, and different stages

of organization in the hemorrhage. Subcapsular bleeding may come from ruptured parenchyma with irregular borders and end up as perforation and massive hemorrhage into the abdominal cavity (demonstration of free fluid in the abdominal cavity).

Capsule injuries. In ultrasonography, injuries solely to the capsule of the liver are detected as gaps in the hepatic contour; however, frequently this direct sign is impossible to demonstrate and the sonographer has to rely on the indirect sign of free fluid in the abdominal cavity increasing in volume during frequent follow-up scans.

Bilioma

It is not possible to differentiate between acute bleeding and collections of bile that may also gather as a result of liver trauma and display the same sonographic characteristics ( 2.8n).

Abscess

An abscess may present as an anechoic mass with distinct posterior enhancement (Fig. 2.64,

2.8x–z).

Fig. 2.64 Abscess, subdiaphragmatic in the right liver lobe; not quite anechoic, slight posterior enhancement; impression of the diaphragm, atelectasis of the basal lung.

Echinococcus Infection

Cystic echinococcosis, also known as unilocular hydatid disease, is due to Echinococcus granulosus (a parasitic tapeworm in canines). Alveolar echinoccocosis, terminating in alveolar hydatid disease, is due to Echinococcus multilocularis (parasitic in foxes and small rodents).

Ultrasonography of cystic echinococcosis demonstrates the characteristics of a complex cyst: thickened, sometimes layered cyst wall, akin to a capsule, with marginal daughter cysts (cyst-within-cyst) and calcification in the wall (pathognomonic). Because of the wall thickness, posterior enhancement is less pronounced or may even be absent, and in calcification there will be posterior shadowing. Old and no longer

vital hydatid cysts may present with different degrees of lumen degradation, bizarre membrane formation, irregular hyperechoic compaction, and also central calcification, or they may exist just as calcified remnants.

In alveolar echinococcosis (multilocular hydatid disease) there is diffuse poorly delimited infiltration of the hepatic parenchyma with inhomogeneous coarse texture, whose more advanced stages involve the vessels and bile ducts, may demonstrate calcification, and can spread from the liver to destroy the diaphragm, lungs, porta hepatis, retroperitoneum, duodenum, and pancreas.

trahepatic criteria such as splenomegaly with infiltrative changes and lymphadenopathy may be seen.

Fig. 2.67 Lymphoma of the liver. Non-Hodgkin lymphoma with multiple hypoechoic masses and one almost completely anechoic lesion.

Infiltrating Lymphoma

Involvement of the liver is seen in about 50% of lymphoma cases (Hodgkin disease and non-Hodgkin lymphoma). Particularly the more advanced stages will demonstrate hepatic involvement with circumscribed malignant lymphadenopathy. Diffuse, miliary, or periportal infiltration of the parenchyma is primarily found in early

stages of the disease and usually escapes ultrasound detection. In diffuse nonspecific parenchymal changes, the presence of splenic pathology and lymphadenopathy may warrant the presumed diagnosis of diffuse infiltrative lymphoma of the liver. This suspicion must then be confirmed by needle biopsy.

Hypoechoic/anechoic malignant lesions or deposits within the liver are highly suspicious for a tumor with a high degree of malignancy and a low degree of differentiation (see below) (Fig. 2.68). Diffuse metastasis of the small nodular type may present as numerous anechoic masses that differ from polycystic liver disease by their irregular shape and diffuse margin. There is no posterior enhancement.

Fig. 2.68 Metastases of neuroendocrine tumors may present as almost anechoic lesions; in color Doppler sonography an intensive vascularity is detectable.

Any differential diagnosis of anechoic masses in the liver has to include the possibility of vessels or bile ducts being viewed in crosssection. In this case, the characteristic aspects are the tubular shape of the lesion when imaged in a cross-section plane, and its course, which can be traced all the way back to the originating vessel/duct. In addition, vessels may be identified by duplex or color-flow duplex scanning as well as CEUS, which can differentiate between an enlarged bile duct or arterial, portal venous, and venous vessels. For reasons of clarity, these anechoic “masses” are listed here.

●Bile ducts. Bile ducts appearing as anechoic masses in the liver have to be pathologically enlarged/engorged (e. g., Caroli disease). These cases are characterized by their periportal location and identification of the socalled hepatic triad, i. e., delineation of a branch of each of the hepatic artery proper and the portal vein as well as the enlarged bile duct.

●Portal vein branches. Being part of the hepatic triad, the branches of the portal vein course through the periportal area as well. Venectasia, varicosities, and collaterals in case of portal hypertension will all be imaged as enlarged segments of the intrahepatic tree of the portal venous system.

●Hepatic vein branches. They are easily identified by their typical course terminating at their stellate junction with the vena cava. The sonographer should keep in mind the possible venectasia and anomalies of the Budd–Chiari syndrome.

●Hepatic artery aneurysms, shunts, and vascular malformation. These may be identified by color-flow duplex scanning and can be differentiated further by CEUS (Fig. 2.69).

Fig. 2.69a–c Demonstration of arteriovenous shunts.

a AV shunt in the right liver lobe in known hereditary hemorrhagic telangiectasia (Osler disease).

b AV malformation (Osler disease): spot-like anechoic masses, gray-scale image.

c Color Doppler sonography: vascular conglomerates.