Hydatid Cysts 

  • Author: Imad S Dandan, MD; Chief Editor: Julian Katz, MD   more...
 
Updated: Nov 28, 2011
 

Background

Hydatid disease is a parasitic infestation by a tapeworm of the genus Echinococcus. It is not endemic in the United States, but the change of immigration patterns and the improvement of transcontinental transportation over the past 4 decades have caused a rise in the profile of this previously unusual disease throughout North America. This has led to the necessity for physicians to be more aware of its clinical features, diagnosis, and management.

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Pathophysiology

Human echinococcosis is a zoonotic infection caused by the tapeworm of the genus Echinococcus. Of the 4 known species of Echinococcus, 3 are of medical importance in humans. These are Echinococcus granulosus, causing cystic echinococcosis (CE); Echinococcus multilocularis, causing alveolar echinococcosis (AE); and Echinococcus vogeli. E granulosus is the most common of the three. E multilocularis is rare but is the most virulent, and E vogeli is the most rare.

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Epidemiology

Frequency

United States

Despite the rise in occurrence, echinococcosis remains a very rare disease (< 1 case per 1 million inhabitants) in the continental United States. Northern Alaska has endemic areas of E granulosus, but the frequency of infection remains low (< 1 case per 100,000 inhabitants).

International

Echinococcosis is also unusual in northern Europe. The endemic areas are the Mediterranean countries, the Middle East, the southern part of South America, Iceland, Australia, New Zealand, and southern parts of Africa; the latter 5 are intensive endemic areas. The incidence of CE in endemic areas ranges from 1-220 cases per 100,000 inhabitants, while the incidence of AE ranges from 0.03-1.2 cases per 100,000 inhabitants, making it a much more rare form of echinococcosis. An epidemiological study of cyctic echinococcosis in Romania emphasized the need for improved preventive measures.[1] Infestation with E vogeli is the most rare form of echinococcosis and is reported mainly in the southern parts of South America.

Mortality/Morbidity

  • Morbidity is usually secondary to free rupture of the echinococcal cyst (with or without anaphylaxis), infection of the cyst, or dysfunction of affected organs. Examples of dysfunction of affected organs are biliary obstruction, cirrhosis, bronchial obstruction, renal outflow obstruction, increased intracranial pressure secondary to mass, and hydrocephalus secondary to cerebrospinal fluid outflow obstruction.
  • In CE, mortality is secondary to anaphylaxis, systemic complications of the cysts (eg, sepsis, cirrhosis, respiratory failure, or operative complications.
  • In clinical cases of AE, the mortality rate is 50-60%. This figure reaches 100% for untreated or poorly treated AE. Sudden death has been reported with AE in asymptomatic patients (autopsy diagnosis).

Race

  • Because of the restricted geographic distribution of the echinococcal worms, persons of certain races are affected more commonly than others; however, the parasite has the capability of infecting persons of all races equally.

Sex

  • No sexual predilection is recognized.

Age

  • The cysts grow slowly, and a cyst is rarely diagnosed during childhood or adolescence unless the brain is affected.
  • CE is a disease of younger adults, with an average age at diagnosis of 30-40 years.
  • AE is a disease of older adults, with an average age at diagnosis of older than 50 years.
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Contributor Information and Disclosures
Author

Imad S Dandan, MD  Consulting Surgeon, Department of Surgery, Trauma Section, Scripps Memorial Hospital

Imad S Dandan, MD is a member of the following medical societies: American Association for the Surgery of Trauma, American College of Surgeons, American Medical Association, American Trauma Society, California Medical Association, and Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Assaad M Soweid, MD, FASGE, FACG  Associate Professor of Clinical Medicine, Endosonography and Advanced Therapeutic Endoscopy, Director, Endoscopy-Bronchoscopy Unit, Division of Gastroenterology, Department of Internal Medicine, American University of Beirut Medical Center, Lebanon

Assaad M Soweid, MD, FASGE, FACG is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Gynecological and Obstetrical Society, and American Medical Association

Disclosure: Nothing to disclose.

Firass Abiad, MD  Head of Division, General and Laparoscopic Surgery, Specialized Medical Center Hospital, Saudi Arabia

Disclosure: Nothing to disclose.

Specialty Editor Board

Ann Ouyang, MBBS  Professor, Department of Internal Medicine, Pennsylvania State University College of Medicine; Attending Physician, Division of Gastroenterology and Hepatology, Milton S Hershey Medical Center

Disclosure: Nothing to disclose.

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

Disclosure: Medscape Salary Employment

Oscar S Brann, MD, FACP  Associate Clinical Professor, Department of Medicine, University of California at San Diego; Consulting Staff, Mecklenburg Medical Group

Oscar S Brann, MD, FACP is a member of the following medical societies: American Gastroenterological Association

Disclosure: Nothing to disclose.

Alex J Mechaber, MD, FACP  Senior Associate Dean for Undergraduate Medical Education, Associate Professor of Medicine, University of Miami Miller School of Medicine

Alex J Mechaber, MD, FACP is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians-American Society of Internal Medicine, and Society of General Internal Medicine

Disclosure: Nothing to disclose.

Chief Editor

Julian Katz, MD  Clinical Professor of Medicine, Drexel University College of Medicine

Julian Katz, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Geriatrics Society, American Medical Association, American Society for Gastrointestinal Endoscopy, American Society of Law, Medicine & Ethics, American Trauma Society, Association of American Medical Colleges, and Physicians for Social Responsibility

Disclosure: Nothing to disclose.

References

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  15. Polo JR, Garcia-Sabrido JL. Sclerosing cholangitis associated with hydatid liver disease. Arch Surg. May 1989;124(5):637. [Medline].

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