Hydatid Cysts Workup

Updated: May 07, 2019
  • Author: Imad S Dandan, MD; Chief Editor: BS Anand, MD  more...
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Workup

Laboratory Studies

The results of routine laboratory blood work are nonspecific. Liver involvement may be reflected in an elevated bilirubin or alkaline phosphatase level. Leukocytosis may suggest infection of the cyst. Eosinophilia is present in 25% of all persons who are infected, while hypogammaglobinemia is present in 30%.

Almost every serodiagnostic technique has been evaluated for echinococcosis, with variable results. Note the following:

  • The indirect hemagglutination test and the enzyme-linked immunosorbent assay (ELISA) have a sensitivity of 80% overall (90% in hepatic echinococcosis, 40% in pulmonary echinococcosis) and are the initial screening tests of choice.

  • Immunodiffusion and immunoelectrophoresis demonstrate antibodies to antigen 5 and provide specific confirmation of reactivity.

  • The ELISA test is useful in follow-up to detect recurrence.

Casoni test

Historically, an intradermal skin test (Casoni test) was used and had a sensitivity of 70%. It is now largely abandoned because of its low sensitivity, low accuracy, and potential for severe local allergic reaction.

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Imaging Studies

Plain films

In cystic echinococcosis (CE), findings from plain films of the chest, abdomen, or any other involved site are, at best, nonspecific and mostly nonrevealing. A thin rim of calcification delineating a cyst is suggestive of an echinococcal cyst.

In alveolar echinococcosis (AE), results from plain films may be normal.

Ultrasonography

Ultrasonography helps in the diagnosis of hydatid cysts when the daughter cysts and hydatid sand are demonstrated. The accuracy of ultrasound evaluations remains operator-dependent.

Computed tomography (CT) scanning

CT scanning has an accuracy of 98% and the sensitivity to demonstrate the daughter cysts. It is the best test for the differentiation of hydatid from amebic and pyogenic cysts in the liver.

In AE, the CT scan findings are sometimes indistinguishable from those of hepatocellular carcinoma.

Magnetic resonance imaging (MRI)

Images show the cysts adequately, but MRI offers no real advantage over CT scanning.

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Procedures

Endoscopic retrograde cholangiopancreatography (ERCP)

ERCP is both diagnostic and therapeutic in patients with intrabiliary rupture of a hydatid cyst, in whom a sphincterotomy can be performed.

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