History

Months or years may pass before an individual exhibits any signs or symptoms of infection with the cystic larval stages.

During the natural course of infection, the fate of E granulosus cysts is variable. Some cysts may grow to a certain size and then persist without noticeable change for many years. Other cysts may rupture spontaneously or collapse and completely disappear.

Spontaneous or traumatic cyst rupture and spillage of viable parasitic tissue during interventional procedures may result in secondary echinococcosis. Cysts may rupture into the peritoneal or pleural cavity, the pericardium, the bile ducts, the gastrointestinal tract, or even blood vessels, leading to extraordinary manifestations and severe complications.

Spontaneous cure of cystic echinococcosis is possible.

After a variable incubation period, infections may become symptomatic if cysts are growing and exerting pressure on adjacent tissue and inducing other pathologic findings.

Sudden symptomatology is usually due to spontaneous or traumatic cyst rupture.

Usually, cysts do not induce clinical symptoms before they have reached a size sufficient to exert pressure on adjacent organs.

Physical

The presentation of human echinococcosis is protean. Patients come to the clinician's attention for different reasons, such as when a large cyst has some mechanical effect on organ function or rupture of a cyst causes acute hypersensitivity reactions. The cyst may also be discovered accidentally during radiographic examination, body scanning, surgery, or for other clinical reasons.^[11]

Common chief symptoms are upper abdominal discomfort and pain, poor appetite, and a self-diagnosed mass in the abdomen. Physical findings are hepatomegaly, a palpable mass if on the surface of the liver or other organs, and abdominal distention. If cysts in the lung rupture into the bronchi, intense cough may develop, followed by vomiting of hydatid material and cystic membranes.^[12]

Liver findings may include the following:

Hepatomegaly
Jaundice
Biliary colic–like symptoms
Cholangitis
Pancreatitis
Liver abscess
Portal hypertension
Ascites
Inferior vena cava compression or thrombosis
Budd-Chiari syndrome
Cyst rupture, peritoneal spread, and peritonitis
Hemobilia
Biliary fistula to skin, bronchial system, or gastrointestinal tract

Lung findings may include the following:

Tumor of chest
Chest pain
Chronic cough, expectoration, and dyspnea
Pneumothorax
Eosinophilic pneumonitis
Pleural effusion
Parasitic lung embolism
Hemoptysis
Biliptysis

Heart findings may include the following:

Tumor
Pericardial effusion
Embolism

Breast masses may be found (must be differentiated from neoplasms).^[11]

Spine masses with neurologic symptoms may be found.

Brain masses with neurologic symptoms may be found.

Causes

See Background for a brief discussion of infection routes.

Susceptibility of humans to infection varies, presumably because of individual differences in nutritional, immunologic, and genetic factors.

Complications

The cysts may rupture, and the cyst content may be released into biliary or bronchial systems. This may cause infection of the cyst and an obstruction of the biliary or bronchial tree with severe clinical consequences (eg, pneumonitis, pleural effusion, pneumothorax, secondary echinococcosis of the pleural and peritoneal cavity).

Differential Diagnoses

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Media Gallery

WHO Informal Working Group on Echinococcosis standardized ultrasound classification of echinococcal cysts. Image courtesy of World Health Organization (WHO).
CE1 cyst in the right segments of the liver in a young Albanian boy
CE3a echinococcal cyst of the liver. Note the folding endocyst ("waterlily sign") typical of CE3a cysts.
CE3b cyst in the right lobe of the liver. The cyst is predominantly solid with a few daughter cysts
CE4 cyst in the liver. The cyst is completely solid and inactive.
CE3b cyst in the muscles of posterior thigh (scanned with a convex ultrasound probe).
CE4 cysts in the peritoneum in a patient with disseminated echinococcosis (longitudinal scan).
Viable scolices (note rostellar hooklets).
CT scan of peritoneal, disseminated echinococcosis
MR scan of echinococcal cyst in the right psoas muscle, infiltrating the adjacent vertebral body
Ultrasound scan of a CE3b subcutaneous cyst located in the lumbar area. The cyst was the subcutaneous extension of a cyst located in the spine that had been previously operated on.
MR of the spine showing CE involvement of CE3,CE4,CE5 vertebral bodies, spinous processes and subcutaneous tissue (same patient as # )
CT scan showing CE infiltration of vertebral bodies and destruction of left peduncles

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Author

Enrico Brunetti, MD Associate Professor, Department of Infectious Diseases, Division of Infectious and Tropical Diseases, University of Pavia, Italy; Staff Physician, Department of Infectious Diseases, IRCCS S Matteo Hospital Foundation, Pavia, Italy

Enrico Brunetti, MD is a member of the following medical societies: American Society of Tropical Medicine and Hygiene, European Society of Clinical Microbiology and Infectious Diseases

Disclosure: Nothing to disclose.

Coauthor(s)

Carlo Filice, MD Chief of Ultrasound Unit, Adjunct Professor, Department of Internal Medicine, Division of Infectious and Tropical Diseases, IRCCS S Matteo Hospital, University of Pavia, Italy

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John W King, MD Professor of Medicine, Chief, Section of Infectious Diseases, Director, Viral Therapeutics Clinics for Hepatitis, Louisiana State University School of Medicine in Shreveport; Consultant in Infectious Diseases, Overton Brooks Veterans Affairs Medical Center

John W King, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Association of Subspecialty Professors, Infectious Diseases Society of America, Sigma Xi, The Scientific Research Honor Society

Disclosure: Nothing to disclose.

Chief Editor

Pranatharthi Haran Chandrasekar, MBBS, MD Professor, Chief of Infectious Disease, Department of Internal Medicine, Wayne State University School of Medicine

Pranatharthi Haran Chandrasekar, MBBS, MD is a member of the following medical societies: American College of Physicians, American Society for Microbiology, International Immunocompromised Host Society, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

Mark R Wallace, MD, FACP, FIDSA Infectious Disease Physician, Skagit Valley Hospital, Skagit Regional Health

Disclosure: Nothing to disclose.