Pictorial review of hepatic echinococcosis: Ultrasound imaging and differential diagnosis

Table 1 Comparison of clinical features between hepatic cystic echinococcosis and hepatic alveolar echinococcosis

	HCE	HAE
Endemic region	Worldwide	North America, northern and central Eurasia
Definitive host	Dogs and other canids	Red foxes and wolves
Intermediate host	Sheep, horses, cows and humans	Rats and humans
Type of growth	Concentric expansive growth	Vesicle-to-vesicle, infiltrative growth
Clinical symptoms	Epigastric discomfort and loss of appetite	Vague abdominal pain (upper right abdomen, 30%), jaundice (25%-30%), fatigue, weight loss, fever and chills
Imaging modalities	Ultrasound, CT, and MRI are used to evaluate the structures adjacent to the lesion, and FDG-PET is used to evaluate the activity of the lesion
Immunological diagnosis	Relatively specific immune response to heat-resistant B antigen, with 20%-58% negative results	Sensitive, positive immune response to specific antigens such as Em2 or Em18, with 90% positive results
Treatment methods and prognosis	Surgical removal of active hydatid cyst to avoid extravasation of cystic fluid, supplemented with drug treatment, with a good prognosis	Radical resection, supplemented with drug therapy, with poor prognosis in the late stage
Postoperative imaging follow-up duration	> 3 years	> 10 years

HCE: Hepatic cystic echinococcosis; HAE: Hepatic alveolar echinococcosis; CT: Computed tomography; MRI: Magnetic resonance imaging; FDG-PET: Fluorodeoxyglucose-positron emission tomography.

Table 2 Sonographic features of hepatic cystic echinococcosis

WHO standardized classification	Disease course and prevalence	Sonographic features
CL	Uncertain, infertile cysts	Fundamental sign: Cystic occupations with indistinct cystic walls
Type CE1	Active, brood capsules; 21%-43%	Special sign: Double cyst wall. Secondary sign: Snowflake
Type CE2	Active, brood capsules; 4%-12%	Special signs: Nested cysts/daughter cysts (wheel-, petal-, or honeycomb-like)
Type CE3a	Transitional, the cysts begin to degenerate; 2%-8%	Special signs: Water lily, cuff sign, and ribbon
Type CE3b	Transitional, the cysts begin to degenerate; 2%-8%	Cystic and solid mass with mixed echogenicity
Type CE4	Inactive, most do not contain viable protoscolex; 10%-27%	Special signs: Ball of wool and cerebral gyri
Type CE5	Inactive, most do not contain viable protoscolex; 1%-11%	Special sign: Eggshell calcified wall

WHO: World Health Organization; CL: Cystic lesions; CE: Cystic echinococcosis.

Table 3 Sonographic features of hepatic alveolar echinococcosis

Course of disease	EMUC-US	Sonographic features
Infiltration stage	Hemangioma-like/metastasis-like	Fundamental sign: A solid, heterogeneously echoic mass with unclear boundaries and an irregular shape
Calcification stage	Hailstorm/ossified	Special sign: A heterogeneously echoic mass with punctate, gravel-like, and small circular echogenic calcifications inside, accompanied by a posterior acoustic shadow
Liquefaction stage	Pseudocystic	Special sign: A heterogeneously echoic mass with large, irregularly shaped dark areas, creating a “lava-like” appearance, referred to as the “cavity” sign

EMUC-US: Echinococcosis multilocularis Ulm classification-ultrasound.

Table 4 Differential diagnosis of solid hepatic echinococcosis

Entities	Medical history	Sonographic features	Laboratory examination
HCE (HCE4, HCE5)	History of travel to endemic areas	B-mode: The mass shows the “cerebral gyri” sign with intermittent hyperechoic and hypoechoic signals, as well as scattered, annular, and “eggshell-like” calcification. CEUS: Most of the masses show no enhancement in both their interior and margins	Heat-resistant B antigen, with 20%-58% negative results
HAE	History of travel to endemic areas	B-mode: An ill-defined, heterogeneously echoic mass with diffuse, scattered, or focal calcification and possible liquefactive necrosis. CEUS: In the AP, an enhanced and irregular “rim-like” peripheral band can be observed surrounding the lesion, with no obvious internal enhancement, presenting as a “black hole” sign	Specific antigens such as Em2 or Em18, with 90% positive results
Hepatic paragonimiasis	History of eating undercooked shrimp and crabs	B-mode: An irregularly shaped and heterogeneous lesion with an internal appearance resembling “tunnel-like” echoes. CEUS: The lesion shows uneven enhancement in the AP, with non-enhancing reticular and “tunnel-like” areas internally	Stool examination
Liver abscess	History of diabetes, high fever, pain upon percussion in the liver area	B-mode: Thick-walled septated cystic lesions with areas of liquefied necrosis, including some with an air-fluid level within the cysts. CEUS: The mature liver abscess shows hyper-enhancement of the cystic wall and internal septa in the AP, with multiple patches of non-enhancing liquefied necrotic areas, resembling a “honeycomb-like” pattern	CBC, CRP
HCC	History of underlying liver disease associated with hepatitis and alcohol intake	B-mode: Swelling growth with a “hump” sign. CEUS: The typical HCC shows uniform hyper-enhancement in the AP and begins to wash out with slightly lower enhancement in the LP	AFP, AT
ICC	History of hepatolithiasis	B-mode: An ill-defined lesion, often accompanied by biliary duct dilation and early metastasis to hepatic hilar lymph nodes. CEUS: The mass-forming ICC shows irregular “rim-like” peripheral enhancement in the AP, washout in the PVP, and significant hypo-enhancement in the LP	CA 19-9
Liver metastases	Mainly arising from primary cancers of the lung, gastrointestinal tract, pancreas, and breast	B-mode: Multiple hypoechoic or hyperechoic masses within the liver. CEUS: The mass shows a thick “rim-like” hyper-enhancement in the early AP, washout in the late AP, and significant hypo-enhancement in the PVP and LP, presenting as a “bull's eye” sign	CEA, CA 72-4, CA 15-3, CA 125, CA 19-9
HBCA	Mainly in middle-aged women	B-mode: The cystic-solid mass with mixed echogenicity has a “multi-room-like” structure, often with solid wall nodules growing towards the cavity. CEUS: The enhancement of the lesion can be observed in “multilocular-like” septa, walls, and wall nodules in the AP	-
HCA	Women who take oral contraceptives	B-mode: A well-defined, homogeneous mass with clear borders. CEUS: The mass shows overall high enhancement in the AP and primarily iso-enhancement in the PVP and LP	-
FNH	Mainly in young and middle-aged women	B-mode: Central scar with a radial distribution within the mass. CEUS: The typical FNH presents as centrifugal enhancement in a “spoke-wheel” or “firework-like” pattern from the center to the periphery in the AP, with slight hyper-enhancement in the PVP and LP	-
HSH	-	B-mode: A “sieve pore-like” hyperechoic mass. CEUS: The typical HSH shows discontinuous, nodular peripheral enhancement in the AP, with progressive partial or complete centripetal fill-in in the PVP and slight hyper-enhancement in the LP. A non-enhancing area can be observed within the lesion	-
Hepatoblastoma	Predominantly in children under five years of age	B-mode: A slightly lobulated, heterogeneously echogenic mass with visible liquefied necrotic areas. CEUS: The mass shows hyper-enhancement in the AP and begins to wash out in the PVP, with no enhancement in the liquefied necrotic zone	AFP

HCE: Hepatic cystic echinococcosis; CEUS: Contrast-enhanced ultrasound; HAE: Hepatic alveolar echinococcosis; AP: Arterial phase; CBC: Complete blood cell count; CRP: C-reactive protein; HCC: Hepatocellular carcinoma; LP: Late phase; AFP: Alpha fetoprotein; AT: Abnormal thrombin; ICC: Intrahepatic cholangiocarcinoma; PVP: Portal venous phase; CA: Carbohydrate antigen; CEA: Carcinoembryonic antigen; HBCA: Hepatic biliary cystadenoma; HCA: Hepatocellular adenoma; FNH: Focal nodular hyperplasia; HSH: Hepatic sclerosing hemangioma.