Ultrasound signs of liver pathology

Liver enlargement/hepatomegaly: with homogeneous echotexture

If the liver is enlarged, but has a normal homogeneous echostructure, this may be due to the following reasons:

1. Heart failure. The hepatic veins will be dilated. There is no change in the diameter of the inferior vena cava with the phase of the respiratory cycle. Look for pleural effusion above the diaphragm.
2. Acute hepatitis. There are no specific echographic signs of acute hepatitis, but the liver may be enlarged and painful. Ultrasound examination may be useful to exclude other liver diseases, and if the patient has jaundice, to differentiate between obstructive and non-obstructive forms. As a rule, ultrasound cannot provide more information if hepatitis is suspected.
3. Tropical hepatomegaly. The only significant finding is an enlarged liver, usually in combination with an enlarged spleen.
4. Schistosomiasis. The liver may be normal or enlarged sonographically, with thickening of the portal vein and its major branches, the walls of which and the tissue around which become more echogenic, especially around the portal vein. The splenic vein may also be enlarged, and if portal hypertension is present, splenomegaly will be present. Collaterals develop at the splenic hilum and along the medial margin of the liver. These appear as tortuous, anechoic, vascular structures that must be distinguished from the fluid-filled bowel. (Observation over a period of time will reveal intestinal peristalsis.) Periportal fibrosis develops with Schistosoma mansoni and S. japonicum.

Enlarged liver: with heterogeneous echotexture

1. Without focal lesions. If there is an increase in the echogenicity of the liver parenchyma with depletion of the vascular pattern of the peripheral branches of the portal vein, cirrhosis of the liver, chronic hepatitis, fatty hepatosis may occur. A liver biopsy may be required to establish an accurate diagnosis. In some cases, the deep parts of the liver are practically not visualized, so the hepatic veins cannot be identified. With a normal echographic picture of the liver, the presence of cirrhosis cannot be excluded.
2. With multiple focal lesions. Multiple focal lesions of varying size, shape and echostructure, creating heterogeneity of the entire liver, are observed in:
   • Macronodular cirrhosis. The liver is enlarged with echogenic lesions of varying size but with normal stroma. The vascular pattern is altered. There is a high risk of malignancy, but this can only be detected by biopsy.
   • Multiple abscesses. Abscesses usually have ill-defined margins, posterior wall enhancement, and internal echotexture.
   • Multiple metastases. May have increased echogenicity, may be hypoechoic with clear contours or unclear contours, may simultaneously have metastases of different echostructures. Metastases are usually more numerous and more varied than abscesses; multinodular hepatocarcinoma can also metastasize.
   • Lymphoma. It can be suspected in the presence of multiple hypoechoic foci in the liver, usually with unclear contours, without distal acoustic enhancement. Ultrasound examination cannot distinguish lymphoma from metastases.
   • Hematomas. They usually have fuzzy edges and distal acoustic enhancement, but when blood clots are organized, hematomas may become hyperechoic. It is important to clarify the presence of a history of trauma or anticoagulant therapy.

It is not easy to differentiate liver abscesses, metastases, lymphoma and hematoma based on ultrasound data alone.

Small liver / shriveled liver

Micronodular cirrhosis of the liver is characterized by diffusely increased echogenicity and distortion due to scarring of the portal and hepatic veins. This is often associated with portal hypertension, splenomegaly, ascites, and dilation and varicose transformation of the splenic vein. The portal vein may have a normal or reduced diameter intrahepatically, but may be enlarged in the extrahepatic region. If internal echostructures are present in the lumen, thrombosis may occur, which extends to the splenic and mesenteric veins. In some patients with this type of cirrhosis, the liver appears normal in the early stages of the disease.

Cystic formations in a normal or enlarged liver

1. Solitary liver cyst with clear contours. An anechoic formation with clear contours, rounded in shape, with acoustic enhancement, usually less than 3 cm in diameter, usually asymptomatic. more often turns out to be a congenital solitary simple liver cyst. However, it is impossible to exclude the presence of a small parasitic cyst, which cannot be differentiated sonographically.
2. Solitary cyst with an "undermined", uneven outline.
3. Multiple cystic lesions. Multiple round lesions of varying diameter, almost anechoic, with clear contours and dorsal acoustic enhancement may occur in congenital polycystic disease. It is necessary to look for cysts in the kidneys, pancreas and spleen; congenital polycystic disease is very difficult to differentiate from parasitic cysts).
4. Complicated cyst. Hemorrhages and suppurations of the cyst can lead to the appearance of an internal echostructure and simulate an abscess and a necrotically changed tumor.
5. Echinococcal cyst. Parasitic disease can give a wide range of echographic changes.

Before performing fine-needle aspiration of a solitary cyst, examine the entire abdominal cavity and obtain a chest x-ray. Parasitic cysts are usually multiple and may be dangerous if aspirated.

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Differential diagnosis of liver lesions

Differentiating hepatocellular carcinoma from multiple liver metastases or abscesses is difficult. The primary cancer usually develops as a single large mass, but multiple masses of varying sizes may also be present, and the echostructures usually have a hypoechoic rim. The center of the mass may be necrotic and appear almost cystic, with fluid-containing cavities and a thick, irregular wall. Sometimes it is very difficult to differentiate such tumors from abscesses.

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Single solid formation in the liver

A variety of diseases can cause the appearance of single solid formations in the liver. Differential diagnosis is sometimes very difficult and in some cases requires biopsy. A single, well-defined hyperechoic formation located under the liver capsule may be a hemangioma: 75% of hemangiomas have dorsal enhancement without acoustic shadowing, but at large sizes they can lose their hyperechogenicity, in which case they are difficult to differentiate from primary malignant liver tumors. Sometimes there are multiple hemangiomas, but they usually do not give any clinical symptoms.

It can be extremely difficult to differentiate a hemangioma from a solitary metastasis, abscess, or parasitic cyst. The absence of clinical symptoms largely indicates the presence of a hemangioma. Computed tomography, angiography, magnetic resonance imaging, or radioisotope scanning with labeled red blood cells may be required to confirm the diagnosis. The absence of other cysts allows us to exclude a parasitic disease. In the presence of internal hemorrhage, the ultrasound image may simulate an abscess.

A single lesion with a homogeneous echotexture and a hypoechoic rim at the periphery is most likely a hepatoma, however, a hepatoma may also have central necrosis or may be presented as a diffuse heterogeneity, or may be multiple and infiltrate the portal and hepatic veins.

Liver abscesses

Differentiation between bacterial abscess, amebic abscess, and infected cyst is difficult. Each may present as multiple or solitary lesions and typically appears as a hypoechoic structure with posterior wall enhancement, irregular border, and internal sediment. Gas may be present in the cavity. Bacterial infection may be superimposed on a cold amebic abscess or may occur in the cavity of a healed amebic abscess. A necrotic tumor or hematoma may also simulate an abscess.

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Amebic abscess

In the early stages of development, amoebic abscesses may be echogenic with an unclear outline or even isoechoic, not visualized. Subsequently, they look like formations with uneven walls and acoustic amplification. Sediment is often determined inside. As the infection progresses, the abscess acquires clearer contours: the sediment becomes more echogenic. Similar changes occur with successful treatment, but the abscess cavity can persist for several years and simulate a cyst. The scar after the healing of an amoebic abscess exists indefinitely and can calcify.

Amebic abscesses in the liver

• Usually single, but can be multiple and of varying sizes.
• Most often found in the right lobe of the liver.
• They are most often found under the diaphragm, but can also occur elsewhere.
• They respond clearly to the introduction of metronidazole or other adequate therapy.
• May be isoechoic and not visualized on initial examination. If abscess is suspected clinically, repeat ultrasound examination after 24 and 48 hours.
• Cannot be clearly differentiated from pyogenic abscesses

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Subdiaphragmatic and subhepatic abscess

An almost completely anechoic, clearly defined, triangular formation between the liver and the right dome of the diaphragm may be a right-sided subphrenic abscess. Subphrenic abscesses can be of different sizes and are often bilateral, so the left subphrenic space should also be examined. When a chronic abscess forms, the contours of the abscess become unclear: septa and internal sediment may be visualized.

When performing an ultrasound examination for fever of unknown origin or fever after surgery, it is necessary to examine both the right and left subdiaphragmatic spaces.

The posterior pleural sinuses should also be examined to rule out the presence of an accompanying pleural effusion (which may also be caused by a purulent or amebic liver abscess). A chest radiograph may be helpful. If a subphrenic abscess is identified, the liver should be examined to rule out an accompanying amebic or subphrenic abscess.

Sometimes a subdiaphragmatic abscess can reach the subhepatic space, most often between the liver and kidney, where it is visualized as the same anechoic or mixed echogenicity structure with internal sediment.

Liver hematomas

Ultrasound is good at detecting intrahepatic hematomas, the echogenicity of which may vary from hyper- to hypoechogenic. However, a relevant history and clinical symptoms may be necessary to differentiate hematomas from abscesses.

Subcapsular hematomas may be represented by anechoic or mixed echogenicity (due to the presence of blood clots) zones located between the liver capsule and the underlying liver parenchyma. The liver contour usually does not change.

Extracapsular hematomas are represented by anechoic or mixed echogenicity (due to the presence of blood clots) zones located close to the liver, but outside the liver capsule. The echographic picture may resemble an extrahepatic abscess.

Any patient with liver trauma may have multiple intraparenchymal hematomas, subcapsular hematomas, or extrahepatic hematomas. Other organs, especially the spleen and kidneys, should be evaluated.

Bilomas

Fluid in or around the liver may be bile resulting from trauma to the biliary tract. It is impossible to differentiate between bilomas and hematomas using ultrasound.