Echinococcosis

Key Features

Essentials of Diagnosis

• Cystic tumors of liver, lungs, kidneys, bones, brain, and other organs

• Eosinophilia

• Urticaria and pruritus if cysts rupture

• Protoscoleces or daughter cysts in the primary cyst

• Positive serology

• Epidemiologic evidence of exposure

General Considerations

• Dogs, cats, and other carnivores are the hosts for Echinococcus granulosus

• Cystic and alveolar echinococcosis (hydatid disease) cause significant morbidity and mortality worldwide

• Endemic areas include Australia, New Zealand, and the southwestern United States, including Native American reservations where shepherding is practiced

• Primary sites of involvement are the liver (60–70%) and the lungs (20–25%)

• A unilocular cyst is most common

• Cysts of Echinococcus multilocularis are multilocular and demonstrate more rapid growth

Clinical Findings

Symptoms and Signs

• Vary and depend primarily on the site, size, and condition of the cysts

• Growth rates of cysts are variable and range between 1 and 5 cm in diameter per year

• Liver cysts

  • Can cause hepatomegaly, right upper quadrant pain, nausea, and vomiting

  • If a cyst ruptures, the sudden release of its contents can result in a severe allergic reaction

  • May cause biliary obstruction

  • Most are in the right lobe

• Rupture of a pulmonary cyst causes

  • Coughing, dyspnea, wheezing, urticaria, chest pain, and hemoptysis

  • Cyst and worm remnants are found in sputum

• Brain cysts may cause focal neurologic signs and convulsions

• Renal cysts cause pain and hematuria

• Bone cysts cause pain

Differential Diagnosis

• Tumors, bacterial or amebic abscess

• Cavitary tuberculosis (pulmonary)

• Mycoses

• Benign cysts

Diagnosis

Laboratory Findings

• Antibody assays

  • Useful to confirm a presumptive diagnosis

  • However, some patients do not have a detectable immune response (related to the integrity of the cyst and sequestration of echinococcal antigens inside the cyst)

• Eosinophilia is present in only about 25% of patients

• Serologic tests are useful for diagnosis and follow-up of therapy

Imaging

• Visualization of daughter cysts is highly suggestive of echinococcosis

• CT, MRI, and ultrasonography are useful for the diagnosis of deep-seated lesions

• Abdominal ultrasonography is most widely used diagnostic tool

• Pulmonary or bone cysts may be visible on plain films

Diagnostic Procedures

• Ultrasonography-guided fine-needle aspiration coupled with parasitologic examination for protoscoleces, rostellar hooks, antigens, or DNA may confirm diagnosis

Treatment

Medication

• Chemotherapy alone has been shown to cure about one-third of patients

• Albendazole

  • Should be initiated for several days prior to surgery

  • Dosage: 15 mg/kg/d divided in two doses for 3 months, maximum 400 mg twice daily

  • Praziquantel is sometimes added

• For alveolar echinococcus, lifetime chemotherapy may be required in some patients (particularly in those in whom complete resection is not possible)