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While the liver is the primary and most often involved organ (99%), hematogenous dissemination may occur to other organs such as lungs (Fig. 3.164), brain and bone in less than 5% of patients. Liver lesions vary from minor foci to large areas of infiltration of 15 to 20 cm diameter or more. Any part of the liver may be infiltrated.

Fig. 3.164 Multiple large hydatid cysts of varying sizes and shapes throughout both lungs and the mediastinum in a patient from India. The appearance resembles metastatic neoplasm, but these were in fact metastatic hydatids. Air is present within several cysts that have ruptured, especially at the lung bases, and there are several air-fluid levels in the right lower hemithorax. Several of these masses have indistinct, irregular margins, suggesting infiltration into the surrounding lung, or pneumonitis adjacent to the lesions. Although E. granulosus infection is by far the most common form of hydatid disease in India, this reportedly was a fatal case due to E. multilocularis.

In most countries, ultrasound will be the primary imaging tool for diagnosing hepatic alveolar echinococcosis (Figs. 3.165-3.168). Weill has described in detail the sonographic findings, noting that necrosis and resulting cyst formation occur in 30% of patients. The necrotic debris, when present, causes a heterogeneous appearance; the lesions are usually much more irregular than those of cystic hydatid disease caused by E. granulosus and do not have a well-defined wall (Figs. 3.165 and 3.166). The multiple cystic complexes are surrounded by abnormal hepatic parenchyma and their outlines are often craggy, so that they may simulate the snowstorm or complex pattern of metastatic disease. Scattered hyperechoic foci are often the result of calcifications, better seen with plain films or CT scanning. The infiltrating character of the disease causes postobstructive dilatation of multiple biliary ducts (Figs. 3.166 and 3.167) as well as narrowing of portal and hepatic veins and, at times, the inferior vena cava (Fig. 3.168), all of which can lead to jaundice and portal hypertension which may require liver transplantation, if available.

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Fig. 3.165 Sonograms of hepatic alveolar echinococcosis. (A) A right coronal section and (B) sagittal section show the typical massive necrosis of the large irregularly marginated lesion with shaggy borders and abnormal adjacent parenchyma (arrowheads and arrows). (C and D) A second patient with marked necrosis of a huge lesion with dependent debris within the cavity and heterogeneous hyperechoic areas bordering the cavity. (Reprinted with permisssion from Weill FS: Ultrasound Diagnosis of Digestive Diseases (ed 3); Springer- Verlag, 1990).

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Fig. 3.166 Hepatic alveolar echinococcosis. (A) Transverse sonogram shows a huge, partially necrosed lesion of the right liver lobe (arrow). (B and C) Oblique and sagittal sections reveal the complex heterogeneous, often hyperechoic nature of the lesions near the dome of the liver (arrows). (D) Sagittal section of the left lobe shows localized dilatation of bile ducts (arrows). (Reprinted with permisssion from Weill FS: Ultrasound Diagnosis of Digestive Diseases (ed 3); Springer- Verlag, 1990).

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Fig. 3.167 Hepatic alveolar echinococcosis. (A) Hyperechoic lesion contains calcifications (open arrow) and obstructs the portal branch (arrowhead). (B) Parallel section also shows hyperechoic calcifications (open arrow) with posterior acoustic shadowing and dilated intrahepatic ducts (arrowhead). (Reprinted with permisssion from Weill FS: Ultrasound Diagnosis of Digestive Diseases (ed 3); Springer- Verlag, 1990).

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Fig. 3.168 (A) Sagittal sonogram shows heterogeneous hyperechoic hepatic lesion of E. multilocularis invading the inferior vena cava (arrows). (B) Transverse intraoperative sonogram shows the lesion (black arrowheads) obstructing the lumen of the vena cava whereas the lumen of the aorta (white arrowhead) is clear. (Reprinted with permisssion from Weill FS: Ultrasound Diagnosis of Digestive Diseases (ed 3); Springer- Verlag, 1990).

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