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Official reprint from UpToDate www.uptodate.com ©2015 UpToDate

AuthorPedro L Moro, MD, MPH

Section EditorPeter F Weller, MD, FACP

Deputy EditorElinor L Baron, MD, DTMH

Clinical manifestations and diagnosis of echinococcosis

All topics are updated as new evidence becomes available and our peer review process is complete.Literature review current through: Jan 2015. | This topic last updated: Oct 21, 2014.

INTRODUCTION — Echinococcal disease is caused by infection with the metacestode stage of the tapewormEchinococcus, which belongs to the family Taeniidae. Four species of Echinococcus produce infection inhumans; E. granulosus and E. multilocularis are the most common, causing cystic echinococcosis (CE) andalveolar echinococcosis (AE), respectively. The two other species, E. vogeli and E. oligarthrus, causepolycystic echinococcosis but have only rarely been associated with human infection.

The clinical manifestations and diagnosis of cystic and alveolar echinococcal infection will be reviewed here.The epidemiology, treatment, and prevention of echinococcosis are discussed separately. (See "Epidemiologyand control of echinococcosis" and "Treatment of echinococcosis".)

CLINICAL MANIFESTATIONS — The Echinococcus species have different geographic distributions andinvolve different hosts. E. granulosus and E. multilocularis also differ in their clinical presentation. (See"Epidemiology and control of echinococcosis".)

Echinococcus granulosus — The initial phase of primary infection is always asymptomatic. Many infectionsare acquired in childhood but do not cause clinical manifestations until adulthood. Latent periods of more than50 years before symptoms arise have been reported. While approximately 50 percent of detected cases occurin asymptomatic patients, many more cases remain undiagnosed or are found incidentally at autopsy.

The clinical presentation of E. granulosus infection depends upon the site of the cysts and their size. Smalland/or calcified cysts may remain asymptomatic indefinitely. However, symptoms due to mass effect withinorgans, obstruction of blood or lymphatic flow, or complications such as rupture or secondary bacterialinfections can result.

Cysts typically increase in diameter at a rate of one to five centimeters per year. However, cyst growth ratesand time courses are highly variable [1,2]. Hydatid cysts may be found in almost any site of the body, eitherfrom primary inoculation or via secondary spread. The liver is affected in approximately two­thirds of patients,the lungs in approximately 25 percent, and other organs including the brain, muscle, kidneys, bone, heart, andpancreas in a small proportion of patients. Single organ involvement occurs in 85 to 90 percent of patients withE. granulosus infection, and only one cyst is observed in more than 70 percent of cases (image 1).

Liver involvement — E. granulosus infection of the liver frequently produces no symptoms. The right lobeis affected in 60 to 85 percent of cases. Significant symptoms are unusual before the cyst has reached at least10 cm in diameter. If the cysts become large, hepatomegaly with or without associated right upper quadrantpain, nausea, and vomiting can result (picture 1).

E. granulosus cysts can rupture into the biliary tree and produce biliary colic, obstructive jaundice, cholangitis,or pancreatitis. (See "Endoscopic diagnosis and management of biliary parasitosis".)

Pressure or mass effects on the bile ducts, portal and hepatic veins, or on the inferior vena cava can result incholestasis, portal hypertension, venous obstruction, or the Budd­Chiari syndrome. (See "Etiology of the Budd­Chiari syndrome".)

Liver cysts can also rupture into the peritoneum, causing peritonitis, or transdiaphragmatically into the pleuralspace or bronchial tree, causing pulmonary hydatidosis or a bronchial fistula. Secondary bacterial infection ofthe cysts can result in liver abscesses. (See "Pyogenic liver abscess".)

Lung involvement — The most common symptoms of pulmonary cystic echinococcosis (CE) described inthe literature include cough (53 to 62 percent), chest pain (49 to 91 percent), dyspnea (10 to 70 percent), and

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hemoptysis (12 to 21 percent). Less frequent symptoms include malaise, nausea and vomiting, and thoracicdeformations [3,4]. The majority of children and adolescents with lung lesions are asymptomatic despite havinglesions of impressive size, assumedly because of a weaker immune response and the relatively higherelasticity of the lung parenchyma relative to older patients [3,5].

Cysts can break or develop secondary bacterial infection. The presence of these complications changes theclinical presentation, either by causing new symptoms or by increasing the severity of existing symptoms. Theprincipal complication is cyst rupture, with spilling of cyst material containing fragments of larval tissue andprotoscolices into the bronchial tree or the pleural cavity. Bronchial tree involvement can lead to cough, chestpain, hemoptysis, or emesis; pleural cavity involvement can cause pneumothorax, pleural effusion, orempyema. Secondary bacterial infection of the cyst can manifest as a pulmonary abscess with poorly definedmargins [6­8].

Approximately 60 percent of pulmonary hydatid disease affects the right lung, and 50 to 60 percent of casesinvolve the lower lobes [9]. Multiple cysts are common. Approximately 20 percent of patients with lung cystsalso have liver cysts [10]. The ratio of lung to liver involvement is higher in children than in adults [10].

Other organs — Involvement of organs outside of the liver or lung is unusual but can lead to significantmorbidity and mortality.

Cyst rupture — Fever and acute hypersensitivity reactions, including anaphylaxis, may be the principalmanifestations of cyst rupture. Hypersensitivity reactions are related to the release of antigenic material andsecondary immunologic reactions. (See "Anaphylaxis: Rapid recognition and treatment".)

Outcome — The outcome of infection varies with the stage of the disease. One study reported on the long­term outcome of 33 patients with asymptomatic liver hydatid cysts [1]. The natural history of infection wasvariable. Approximately 15 percent of patients had undergone surgery 10 to 12 years after the initial diagnosis.Among patients who did not undergo surgery, 75 percent remained asymptomatic; 57 percent did not have achange in the size of the cyst by imaging.

Calcification usually requires 5 to 10 years to develop and occurs most commonly with hepatic cysts but rarelywith pulmonary or bone cysts. Total calcification of the cyst wall suggests that the cyst may be nonviable.

Echinococcus multilocularis — Infection due to E. multilocularis is usually symptomatic, although theclinical manifestations are frequently nonspecific. The most common presenting complaints include malaise,weight loss, and right upper quadrant discomfort due to hepatomegaly. Cholestatic jaundice, cholangitis, portalhypertension, and the Budd­Chiari syndrome can also occur. The clinical presentation may mimic that ofhepatocellular carcinoma.

Extrahepatic primary disease is very rare (1 percent of cases). Multiorgan disease was described in 13 percentof cases in one series in which metacestodes involved the lungs, spleen, or brain in addition to the liver [20].Immunodeficiency, such as HIV or transplantation, may accelerate the manifestations of alveolarechinococcosis [21].

If left untreated, more than 90 percent of patients will die within 10 years of the onset of clinical symptoms, and

Infection of the heart can result in mechanical rupture with widespread dissemination or pericardialtamponade [11,12].

Central nervous system involvement can lead to seizures or signs of raised intracranial pressure;infection of the spinal cord can result in spinal cord compression [13].

Cysts in the kidney can cause hematuria or flank pain [14]. Immune complex­mediated disease,glomerulonephritis leading to the nephrotic syndrome, and secondary amyloidosis have also beendescribed [15,16].

Bone cysts are usually asymptomatic until a pathologic fracture develops; the spine, pelvis, and longbones are most frequently affected [17].

Ocular cysts also occur [18,19].

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virtually 100 percent will die by 15 years [22]. Since treatment with albendazole has been introduced, theprognosis has improved considerably. Of 117 patients from France who underwent long­term follow­up, theactuarial survival rate was 88 percent [23]. Life expectancy has improved, and patients undergoing radicaltreatment have a better outcome now than 40 years ago. In Switzerland in 1970, the life expectancy for anaverage 54­year­old patient with echinococcosis was estimated to be reduced by 18 and 21 years for men andwomen, respectively; by 2005, life expectancy was reduced by approximately 3.5 and 2.6 years for men andwomen, respectively [23].

DIAGNOSIS — Both cystic and alveolar Echinococcus may be diagnosed with a combination of imaging andserology [24]. Serologic assays for E. multilocularis infection are more sensitive and specific than for E.granulosus infection. The following discussion primarily deals with the more common E. granulosus infection,except as indicated. Specific discussion related to the diagnosis of alveolar echinococcosis follows below.

E. granulosus — Nonspecific leukopenia or thrombocytopenia, mild eosinophilia, and nonspecific liver functionabnormalities may be observed but are not diagnostic. Eosinophilia is observed in fewer than 15 percent ofcases and generally occurs only if there is leakage of antigenic material.

Imaging — Hydatid cysts may be visualized and evaluated with ultrasonography, computed tomography(CT), or magnetic resonance imaging (MRI). Ultrasonography is employed most widely because it is easy toperform and relatively inexpensive. Portable ultrasound machines are frequently used for screening patients incommunities in which E. granulosus infection is endemic, sometimes with confirmatory serologic testing tomaximize the diagnostic yield [25]. However, CT or MRI may be useful for circumstances in which greateranatomic detail is needed to establish the location and number of cysts, the presence or absence of daughtercysts, and presence of ruptured or calcified cysts, which are important for guiding management (table 1).

Plain radiography may demonstrate calcification within a cyst but cannot detect uncalcified cysts so is notadequate for definitive diagnostic evaluation.

Ultrasonography — The sensitivity of ultrasonography for evaluation of Echinococcus is 90 to 95percent [26,27]. The most common appearance on ultrasound is an anechoic, smooth, round cyst, which canbe difficult to distinguish from a benign cyst. In the presence of liver cyst membranes, mixed echoes can beconfused with an abscess or neoplasm. In the presence of daughter cysts, characteristic internal septation canbe seen.

Shifting the patient's position during ultrasonography may demonstrate "hydatid sand," which consistspredominantly of hooklets and scolexes from the protoscolices. Hydatid disease is probable in the setting ofhydatid sand, inner cyst wall infoldings, and separation of the hydatid membrane from the wall of the cystobserved on ultrasound [28].

Ultrasound allows classification of the cyst(s) as active, transitional, or inactive based on biologic activity;such categorizations may influence the choice of treatment (image 2). Characteristics suggestive of an inactivelesion include a collapsing, flattened elliptical cyst (corresponds to low pressure within the cyst), detachment ofthe germinal layer from the cyst wall ("water lily sign"), coarse echoes within the cyst, and cyst wallcalcification [29,30]. Cysts with a calcified rim may have an "eggshell" appearance.

Several other classification systems are based upon ultrasound appearance (image 2):

WHO categories CE1 and CE2 are active cysts. Type CE1 is unilocular and type CE2 is multilocular withdaughter cysts (figure 1). Class CE3 consists of cysts that are thought to be degenerating (transitional group).There are two types of CE3: CE3a, featuring the "water­lily" sign for floating membranes, and CE3b, which ispredominantly solid with daughter cysts. Establishing whether daughter cysts are present is important forguiding treatment. In addition, nuclear magnetic resonance has demonstrated that CE3a and CE3b have

The World Health Organization (WHO) classification characterizes cysts by type and size (table 1)[31,32].

The Gharbi classification divides cysts into five types [33]. Type I cysts consist of pure fluid; type II havea fluid collection with a split wall; type III cysts contain daughter cysts (with or without degenerated solidmaterial); type IV have a heterogeneous echo pattern; and type V have a calcified wall [33].

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different metabolic characteristics [34]. Classes CE4 and CE5 are considered inactive. By ultrasonography,they are echogenic with increasing degrees of calcification and are nearly always nonviable.

It is important to establish whether daughter cysts (cysts that have involuted from the wall and reside withinthe larger cyst) are present and to distinguish them from brood capsules, which are attached to the wall of thelarger cyst. This distinction is important for guiding treatment.

Lung cysts may be single or multiple, usually do not calcify, rarely lead to daughter cyst formation, and maycontain air if the cyst has ruptured.

Computed tomography — Many reports suggest that computed tomography (CT) has higher overallsensitivity than ultrasonography (95 to 100 percent) [26,27,35]. CT is the best mode for determining thenumber, size, and anatomic location of the cysts and is better than ultrasound for detection of extrahepaticcysts. CT may also be used for monitoring lesions during therapy and to detect recurrences (image 1) [36].

CT may be superior to ultrasonography in assessing for complications such as infection and intrabiliary rupture[37]. In one study, ultrasound performed better than CT in the investigation of the cyst wall, hydatid sand,daughter cysts, and splitting of the cyst wall, while CT was superior for detecting gas and minute calcificationswithin the cysts, in attenuation measurement, and in anatomic mapping [30,38].

Magnetic resonance imaging — Magnetic resonance imaging (MRI) has no major advantage over CTfor evaluation of abdominal or pulmonary hydatid cysts, except in defining changes in the intra­ andextrahepatic venous system [39]. MRI may delineate the cyst capsule better than CT and may be better atdiagnosing complications, particularly for cysts with infection or biliary communication. However, MRI isusually not required and, in most instances, is not cost effective [40­42].

Both CT and MRI are useful in diagnosing echinococcal infection in other sites such as in the brain [43].

Other — Other imaging techniques such as cholangiography may be indicated to diagnose biliaryinvolvement, particularly in patients with cholestatic jaundice. Endoscopic retrograde cholangiopancreatography(ERCP) or magnetic resonance cholangiopancreatography (MRCP) is frequently performed in patients with livercysts prior to intervention to ascertain potential involvement of the biliary system and to guide the treatmentapproach. (See "Endoscopic diagnosis and management of biliary parasitosis".)

Serologic and antigen assays — Serology is useful for primary diagnosis and for follow­up after treatment[20,44,45]. Antibody detection is more sensitive than antigen detection for diagnosis of E. granulosus [20].

Laboratory serologic tools — Diagnostic serologic techniques include:

The sensitivity and specificity of a number of the serologic tests have been compared (table 2). ELISA appearsto be the most sensitive and specific of the available assays [46­51]:

Complement fixationIndirect hemagglutination (IHA)Indirect immunofluorescenceLatex agglutinationDouble diffusion immunoelectrophoresisCounter­current immunoelectrophoresis (CIEP)Radioimmunoassay (RIA)Enzyme­linked immunosorbent assay (ELISA)Enzyme­linked immunoelectrodiffusion assay (ELIEDA)Time­resolved fluoroimmunoassay (TR­FLA)Immunoblot

One study of 79 patients with surgically confirmed pulmonary hydatidosis demonstrated that IgG ELISAwas the most sensitive (84 percent), followed by IgM ELISA (62 percent), passive hemagglutination (61percent), latex agglutination (58 percent), immunoelectrophoresis (51 percent), and specific IgE ELISA (44percent). The specificity of all tests was 98 to 100 percent. Specific IgG ELISA had the highest negative

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The methods most frequently employed for initial screening tests (using crude antigens such as hydatid fluid orprotoscolex extracts) are ELISA and IHA. Confirmatory tests using specific antigens can then be performed,such as immunoelectrophoresis and immunoblotting [48]. Additional tests using recombinant or purifiedspecies­specific antigens may also be useful diagnosis [52].

Simple, heat­stable, inexpensive tests, such as hydatid antigen dot immunoassays, are often used for fieldtesting and population screening [53]. The dot­ELISA has a reported sensitivity of 88 to 96 percent and aspecificity of 90 to 98 percent [54­56].

Two major E. granulosus antigens utilized in serologic testing include antigen 5 and antigen B:

The sensitivity of these antigens in ELISA assays is 60 to 90 percent and the specificity is usuallyapproximately 90 percent [60]. The sensitivity in immunoblot and gel diffusion assays is approximately 90percent with a specificity of 97 to 100 percent [59,61]. One study demonstrated that the immunoblot with theantigen B­rich fraction was positive in 92 percent of patients with E. granulosus but was also positive in 79percent of patients with E. multilocularis [62]. No cross­reactivity was observed with sera from patients withother parasitic diseases, malignancies, or healthy controls.

A variety of issues influence the rates of false­positive and false­negative serologic results. First, there is alack of standardization among different laboratories; for example, one study showed that ELISA using antigenB had a sensitivity of 63 percent, whereas immunoblotting using the same antigen had a sensitivity of 80percent [63]. Second, methods of antigen isolation and purification can influence the results. Third, serologicalassays with high sensitivity and specificity for diagnosis of cystic echinococcosis in clinical settings can beless useful in epidemiological studies; these assays may detect only half of liver cysts in field surveys and asfew as 20 percent of lung cysts [64,65].

The utility of serology can be improved by using a combination of tests or sequential testing [66]. Testsemploying a number of recombinant antigens are being evaluated to improve the sensitivity and specificity ofthe commercially available serologic tests. A highly sensitive assay, usually an ELISA or indirecthemagglutination test, is commonly used as an initial screen, followed by a highly specific immunoblot or geldiffusion assay for confirmation. Testing for specific antibodies, such as specific IgG1 or IgG4 rather than totalIgG, may improve specificity [63,67­69].

Clinical factors — A negative serologic test generally does not rule out echinococcosis. There is noconsistent correlation between serologic results and the number or size of cysts [46]. In general, liver cystselicit an antibody response more frequently than lung cysts. Overall, approximately 85 to 95 percent of livercysts and 65 percent of lung cysts are associated with positive serology, although this varies with the specificserologic test used and cyst activity [47]. Brain, eye, and splenic cysts often do not produce detectable

predictive value (93 percent) [46].

One study compared eight serologic tests among 131 patients with E. granulosus infection [49]. IgGELISA was the most sensitive (94 percent) and specific (99 percent) for the majority of cyst locations.

One report compared six different serologic tests for the diagnosis of cystic hydatid disease among 243patients with surgically confirmed infection [50]. The two ELISA tests gave identical results, with asensitivity of 89 percent for liver cysts and 78 percent for lung cysts. In the 39 patients with false­negative results, the use of immunoblotting only increased the yield by 8 percent; ELIEDA did not identifyany additional cases.

Antigen 5 is a major parasite antigen found on the inner aspect of the germinal layer, brood capsule, andprotoscolices. Only a few studies have assessed the value of tests based on recombinant antigen 5,which has relatively low specificity, although it is used quite extensively for diagnosis in clinical practice[48].

Antigen B is a highly immunogenic polymeric lipoprotein. Studies have showed that antigen B shows ahigh degree of genetic variability [57]. It offers greater specificity than detection of antigen 5; however,neither antigen is specific for E. granulosus per se despite a very high specificity for echinococcalinfection [58,59].

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antibodies, whereas bone cysts frequently are associated with positive serology. Serology is less likely to bepositive with cysts at any site if the cysts are intact, calcified, or nonviable.

The likelihood of false­negative results is variable depending on the lesion site of the lesion and the integrityand viability of the cyst. Antigen­antibody complexes that "mop" up all antibodies may lead to false­negativereactions. Children and pregnant women more frequently have negative serology than other patient populations[9]. False­positive reactions are more likely in the presence of other helminth infections (such as Taeniasaginata, Taenia solium, and particularly neurocysticercosis), cancer, and immune disorders.

Antigen assays — A variety of purified or recombinant diagnostic antigens have been evaluated.Demonstration of antigens in cystic fluid or serum can also be used for diagnosis of primary infection or relapse[66,70,71]. However, up to 50 percent of patients with echinococcal cysts do not have circulating antigens.Latex agglutination or a dot­ELISA to detect echinococcal antigens from cyst fluid have excellent sensitivityand specificity [72­74]. Antigen assays and tests for circulating immune complexes are not widely available butmay become useful secondary tests in the future [75].

E. multilocularis — Nonspecific leukopenia or thrombocytopenia, mild eosinophilia, and nonspecific liverfunction abnormalities may be detected but are not diagnostic. Hypergammaglobulinemia and elevated serumIgE levels are present in more than 50 percent of cases.

Imaging — The diagnosis of E. multilocularis is generally made by imaging techniques in conjunction withserology. On ultrasound or CT, the lesions usually have an irregular contour with no well­defined wall, centralnecrosis, and irregular intralesional and wall calcifications. They may be difficult to distinguish from a tumor,but the patient's overall condition is usually better than would be expected for a malignancy.

Obstruction of the inferior vena cava or of the portal venous system may be evident, which may be more easilyappreciated on MRI. Lung, brain, and bone lesions may also be detected.

Serology — Serologic tests are more reliable for diagnosis of E. multilocularis infection than for E.granulosus infection; sensitivity and specificity rates are 95 to 100 percent [76]. A specific E. multilocularisantigen such as the affinity purified Em2 antigen from AE metacestodes is often used; the Em2­ELISA candiscriminate between E. granulosus and E. multilocularis in 95 percent of cases. Serology usually remainspositive indefinitely; following complete surgical resection, serology may normalize within a few years [77]. TheEm2­ELISA frequently becomes negative within four years of surgery and becomes positive again in thesetting of a recurrence [76,78,79]. An Em2plus­ELISA assay uses additional species­specific antigens; it hassensitivity and specificity of 97 and 99 percent, respectively, and is also useful for monitoring recurrencefollowing surgical resection [80­82]. These tests may not be readily available and may be found only inspecialized centers.

ELISA and immunoblot studies using Em 18, an 18­kD protoscolex antigen, are sensitive and highly speciesspecific [62,83­87]. The antigen is also useful for differentiating between active and inactive infection and isuseful for follow­up of patients on treatment [82,83,88,89].

Clinical recurrence is frequently associated with rising serologic titers. IgG1 and IgG4 antibodies are the mostsensitive isotypes for monitoring success of therapy [83].

Cyst aspiration or biopsy — In the absence of a positive serologic test, percutaneous aspiration or biopsymay be required to confirm the diagnosis by demonstrating the presence of protoscolices, hooklets, or hydatidmembranes. Percutaneous aspiration of liver cyst contents is associated with very low rates of complications,but this method of diagnosis is generally reserved for situations when other diagnostic methods areinconclusive because of the potential for anaphylaxis and secondary spread of the infection [90­93].

Active cysts have clear, watery fluid containing scolices and elevated pressure; inactive cysts have cloudyfluid without detectable scolices and do not have elevated pressure [29]. In the setting of lung cysts,protoscolices or degenerated hooklets may be demonstrable in sputum or bronchial washings. A variety ofstaining methods to detect parasitic material can be used. Stains for visualization of hydatid elements includeRyan trichrome blue stain and modified Baxby stain. Ziehl­Neelsen stain is also useful; under green excitationlight (546 nm), the hydatid elements have a fluorescent bright red appearance [94].

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If aspiration is required, it should be performed under ultrasound or CT guidance; complications can beminimized by concurrent administration of albendazole and praziquantel [95]. (See "Treatment ofechinococcosis".)

Polymerase chain reaction — Polymerase chain reaction (PCR) techniques are limited to research settingsbut may play a diagnostic role in the future [96]. DNA probes using Southern hybridization tests are also beingdeveloped [80].

DIFFERENTIAL DIAGNOSIS — In general, any mass occupying lesion may clinically resemble anechinococcal cyst. The differential diagnosis of cystic echinococcosis includes [97]:

The differential diagnosis of alveolar Echinococcus includes:

SUMMARY

Simple benign cyst – Patients with symptomatic liver cyst may present with abdominal discomfort, pain,or nausea. Liver cysts are distinguished from Echinococcus by ultrasonography. (See "Diagnosis andmanagement of cystic lesions of the liver".)

Hemangioma – Hemangioma is usually an incidental finding identified in the setting of radiographicimaging or laparotomy; the most common symptoms are abdominal pain and right upper quadrantfullness. The diagnosis of hemangioma is generally established radiographically. (See "Hepatichemangioma".)

Hepatocellular carcinoma – Patients with hepatocellular carcinoma are usually asymptomatic in the earlystages; they are distinguished from patients with cystic Echinococcus based on clinical history andimaging. (See "Clinical features and diagnosis of primary hepatocellular carcinoma".)

Abscess – A liver or lung abscess may resemble an Echinococcus cyst clinically and radiographically.Liver abscess is evaluated by aspiration; lung abscess may be evaluated via bronchoscopy or aspiration.In the setting of suspicion for echinococcosis, percutaneous aspiration or biopsy should be reserved forsituations when other diagnostic methods are inconclusive because of the potential for anaphylaxis andsecondary spread of the infection. (See "Pyogenic liver abscess" and "Lung abscess".)

Tuberculosis – A cavitary tuberculosis lesion may resemble an Echinococcus cyst on radiographicimaging. The diagnosis of tuberculosis is established based on the presence of acid­fast bacilli on smearand culture. (See "Clinical manifestations and evaluation of pulmonary tuberculosis".)

Cirrhosis – Patients with cirrhosis may have anorexia, weight loss, weakness, and fatigue; patients withalveolar Echinococcus may have malaise, weight loss, and right upper quadrant discomfort. The two aredistinguished based on radiographic imaging and laboratory data. (See "Cirrhosis in adults: Etiologies,clinical manifestations, and diagnosis".)

Malignancy (hepatocellular carcinoma or liver metastases) – Patients with liver tumors are generallydistinguished from those with alveolar Echinococcus based on radiographic imaging. (See "Solid liverlesions: Differential diagnosis and evaluation".)

E. granulosus infection is initially asymptomatic and may remain so for many years. Subsequent clinicalfeatures and complications depend upon the site and size of the cyst(s). The liver and lungs are affectedin approximately 67 and 25 percent of cases, respectively. Most patients have single organ involvement,and a single cyst is present in more than 70 percent of cases. The long­term outcome is variable andmany patients remain asymptomatic. (See 'Echinococcus granulosus' above.)

E. multilocularis infection is more likely to be symptomatic than E. granulosus infection. The mostcommon clinical manifestations include right upper quadrant discomfort, malaise, and weight loss, andthe picture may mimic that associated with hepatocellular carcinoma. In the absence of treatment, morethan 90 percent of patients with alveolar echinococcosis die within 10 years of the onset of clinicalsymptoms. (See 'Echinococcus multilocularis' above.)

The diagnosis of echinococcosis is typically established by ultrasound imaging (table 1 and image 2) in

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ACKNOWLEDGMENT — The editorial staff at UpToDate, Inc. would like to acknowledge Dr. Karin Leder andDr. Peter Weller, who contributed to an earlier version of this topic review.

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16. Gelman R, Brook G, Green J, et al. Minimal change glomerulonephritis associated with hydatid disease.Clin Nephrol 2000; 53:152.

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combination with serologic testing (usually enzyme­linked immunosorbent assay [ELISA]). Hydatiddisease is probable in the setting of ultrasound demonstrating infoldings of the inner cyst wall, separationof the hydatid membrane from the wall of the cyst, or hydatid sand. E. multilocularis lesions may have anirregular contour and may be difficult to differentiate from tumor. (See 'Ultrasonography' above.)

Diagnostic judgment must take into consideration the limitations of serologic testing. The likelihood of apositive serology depends on cyst location and viability. Patients with liver cysts are more likely to beseropositive than patients with lung cysts. Serologic assays are less likely to be positive in the setting ofcalcified or nonviable cysts. In addition, the sensitivity and specificity of serology is greater for E.multilocularis than for E. granulosus. (See 'Serologic and antigen assays' above.)

Percutaneous aspiration or biopsy should be reserved for situations when other diagnostic methods areinconclusive because of the potential for anaphylaxis and secondary spread of the infection. If aspirationis required, it should be performed under ultrasound or CT guidance. Complications can be minimized byconcurrent administration of albendazole and praziquantel. (See 'Cyst aspiration or biopsy' above.)

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Topic 5669 Version 12.0

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GRAPHICS

Echinococcal cyst of the liver

A computed tomogram shows a multilocular cyst in the liver of a patient withhydatid disease.

Reproduced with permission from: Sun T. Parasitic Disorders: Pathology, Diagnosis, andManagement, 2nd edition. Baltimore: Lippincott Williams & Wilkins, 1999. Copyright © 1999Lippincott Williams & Wilkins.

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Macroscopic appearance of echinococcal cysts inliver tissue

Reproduced with permission from: Craig PS, McManus DP, Lightlowlers MW, etal. Prevention and control of cystic echinococcosis. Lancet Infect Dis 2007;7:385. Copyright ©2007 Elsevier.

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World Health Organization classification of cystic Echinococcus(CE) and treatment stratified by cyst stage

WHOstage

Description Stage SizePreferredtreatment

Alternatetreatment

CE1 Unilocular unechoiccystic lesion withdouble line sign

Active <5 cm Albendazolealone

PAIR

>5 cm Albendazole +PAIR

PAIR

CE2 Multiseptated, "rosette­like" "honeycomb" cyst

Active Any Albendazole +either modifiedcatheterizationor surgery

Modifiedcatheterization

CE3a Cyst with detachedmembranes (water­lily­sign)

Transitional <5 cm Albendazolealone

PAIR

>5 cm Albendazole +PAIR

PAIR

CE3b Cyst with daughtercysts in solid matrix

Transitional Any Albendazole +either modifiedcatheterizationor surgery

Modifiedcatheterization

CE4 Cyst with heterogenoushypoechoic/hyperechoiccontents; no daughtercysts

Inactive Any Observation ­

CE5 Solid plus calcified wall Inactive Any Observation ­

Albendazole is dosed 10 to 15 mg/kg per day in two divided doses; the usual dose foradults is 400 mg twice daily. Duration of therapy is discussed in the text.

PAIR: Puncture, Aspiration, Injection, Reaspiration; WHO: World Health Organization.

Data from:1. Junghanss T, da Silva AM, Horton J, et al. Clinical management of cystic echinococcosis: state

of the art, problems, and perspectives. Am J Trop Med Hyg 2008; 79:301.2. Brunetti E, Kern P, Vuitton DA, Writing Panel for the WHO­IWGE. Expert consensus for the

diagnosis and treatment of cystic and alveolar echinococcosis in humans. Acta Trop 2010;114:1.

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Ultrasonographic classification of cysts due to cystic echinococcus

(Panel CL) Consists of unilocular, cystic lesion(s) (CL) with uniform anechoic content. The cyst wall is notclearly visible; lesions are usually round but may be oval. If these lesions are caused by cystic echinococcus atan early stage of development they are usually not fertile. Definitive diagnosis cannot be made by ultrasoundfindings alone. (Panel CE1) Consists of unilocular, simple cyst with uniform anechoic content. The cyst wall is visible; lesionsare round or oval. Cyst may exhibit fine echoes due to shifting of brood capsules called hydatid sand ("snowflake sign"). (Panel CE2) Consists of multivesicular, multiseptated cysts. The cyst wall is normally visible; lesions are roundor oval. Septations produce "wheel­like" structures. The presence of daughter cysts is indicated by rosette­likeor honeycomb­like structures. Daughter cysts may partly or completely fill the unilocular mother cyst. (Panel CE3) Consists of a unilocular cyst which may contain daughter cysts. Anechoic content with detachmentof laminated membrane from the cyst wall may be visible as floating membrane or as "water­lily sign" which isindicative of wavy membranes floating on top of remaining cyst fluid. The cyst form may be less round becauseof decreased intracystic pressure. The cyst which may degenerate further or may give rise to daughter cysts. (Panel CE4) Consists of heterogenous hypoechoic or hyperechoic degenerative contents; no daughter cysts arepresent. A "ball of wool" sign may be seen which is indicative of degenerating membranes. Most cysts of thistype are not fertile. Definitive diagnosis cannot be made by ultrasound findings alone. (Panel CE5) Cysts characterized by a thick calcified wall that is arch shaped, producing a cone shaped shadow.The degree of calcification varies from partial to complete. These cysts are not fertile in most case. Definitivediagnosis cannot be made by ultrasound findings alone.

World Health Organization Informal Working Group on Echinococcosis (WHO­IWGE) standardized classification of Echinococcalcysts. PAIR: Puncture, Aspiration, Injection, Re­Aspiration: An option for the treatment of Cystic Echinococcosis.WHO/CDS/CSR/APH/2001.6. World Health Organization 2001. Copyright © 2001.

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Structure of the echinococcal cyst

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Sensitivity of serologic tests for echinococcosis at different sites

Site of lesion Sensitivity of serologic tests

Liver IgG ELISA: 80 to 90 percent

IgE ELISA: 82 to 92 percent

Latex agglutination: 65 to 75 percent

Hemagglutination: 80 to 90 percent

Immunoblot (using antigen 5 and/or a B­rich fraction): 80 to 90 percent

Enzyme­linked immunotransfer blot: 80 percent

Lung IgG ELISA: 60 to 85 percent

IgE ELISA: 45 to 70 percent

Latex agglutination: 50 to 70 percent

Hemagglutination: 50 to 70 percent

Immunoblot (using antigen 5 and/or a B­rich fraction): 55 to 70 percent

Enzyme­linked immunotransfer blot: 55 percent

Ig: immunoglobulin; ELISA: enzyme­linked immunosorbent assay.

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Disclosures: Pedro L Moro, MD, MPH Nothing to disclose. Peter F Weller, MD, FACPGrant/Research/Clinical Trial Support: NIH [EGPA (Mepolizumab)]. Consultant/Advisory Boards: GSK[EGPA (Mepolizumab)]. Elinor L Baron, MD, DTMH Employee of UpToDate, Inc.Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, theseare addressed by vetting through a multi­level review process, and through requirements forreferences to be provided to support the content. Appropriately referenced content is required of allauthors and must conform to UpToDate standards of evidence.Conflict of interest policy

Disclosures