eMedicine Specialties > Infectious Diseases > Parasitic Infections

Echinococcosis Hydatid Cyst: Treatment & Medication

Author: Enrico Brunetti, MD, Assistant Professor, Department of Internal Medicine, Division of Infectious and Tropical Diseases, University of Pavia School of Medicine, Italy
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
Contributor Information and Disclosures

Updated: Mar 28, 2008

Treatment

Medical Care

• Two benzimidazolic drugs, mebendazole and albendazole, are the only anthelmintics effective against cystic echinococcosis. Albendazole and mebendazole are well tolerated but show different efficacy.  
  • Albendazole is significantly more effective than mebendazole in the treatment of liver cysts. Benzimidazole treatment alone requires prolonged administration over many weeks, with an unpredictable outcome in terms of response rates in individuals.
  • Treatment with albendazole in E granulosus infection can result in an apparent cure in as many as 30% of patients, with a further 40-50% of patients showing objective evidence of response when observed short term. Patients who do not show obvious initial evidence of response may be found to be cured when observed over several years.
• Duration of therapy and doses are also important. Albendazole efficacy increases with courses of up to 3 months in the more common cyst sites.
• Patients once received these drugs in cycles of 4 weeks separated by 1-2 weeks without drugs. This regimen is no longer advocated given the parasitostatic activity of benzimidazoles and their safety as shown by cumulative data from several retrospective studies. Continuous treatment is preferred and has been administered for periods of up to 2 years without significant side effects.⁵
• The safety profile shows that liver function abnormalities are common, although they rarely limit treatment, while occasional hematologic changes affecting white cells may be more serious. The safety data supply the rationale for monitoring patients during treatment.
• Overall, albendazole has been demonstrated to be a useful advance in the management of cystic echinococcosis when used as sole treatment or as an adjunct to surgery or other treatments.
• Praziquantel has recently been suggested, administered additionally once per week in a dose of 40 mg/kg during treatment with albendazole. However, available data are limited.

Surgical Care

• Surgery was the only treatment available before the introduction of anthelmintic drugs. It is considered the first choice of treatment for echinococcosis but is associated with considerable mortality (up to 2% in some series, increasing with second and further operations), morbidity, and recurrence rates (2-25%). Given the more frequent detection of early and asymptomatic E granulosus liver lesions, a widened indication for chemotherapy exists.
• Several procedures have been described for the treatment of hepatic echinococcal cysts, ranging from simple puncture to liver resection and transplantation, although the most commonly used technique is total or partial cystopericystectomy.
• Usually, radical surgery (total pericystectomy or partial hepatectomy) is indicated for liver cysts. Conservative surgery (open endocystectomy with or without omentoplasty) or palliative surgery (simple tube drainage of infected cysts or communicating cysts) is also an option. More radical interventions have higher intraoperative risks but less numerous relapses. With the inclusion of chemotherapy prior to or after surgery, less-aggressive surgery may be possible.
• Surgery for pulmonary cysts includes extrusion of cysts using Barrett technique (intact endocystectomy without preliminary aspiration), pericystectomy, and lobectomy.
• Peripheral and unilobar echinococcal cysts, regardless of how complicated they are, can also be treated with laparoscopic surgery using partial cystopericystectomy and drainage.⁶ When surgery cannot be avoided, presurgical use of albendazole reduces risk of recurrence and facilitates surgery by reducing intracystic pressure.
• Minimally invasive treatment involves the following:  
  • The puncture of echinococcal cysts has long been discouraged because of risks of anaphylactic shock and spillage of the fluid; however, as experience with ultrasonography-guided interventional techniques has increased since the early 1980s, an increasing number of articles have reported its effectiveness and safety in treating abdominal, especially liver, echinococcal cysts. At least 4209 cysts have been punctured, either for diagnostic or therapeutic purposes, and 16 cases of anaphylactic shock (2 of them lethal [0.047%]) have been reported. Peritoneal seeding has never been reported.
  • Under albendazole coverage, cysts are punctured under ultrasonographic or CT guidance either with a needle or with a catheter according to their size. The presence of an anesthesiologist who intervenes in case of allergic manifestations or anaphylactic shock is mandatory. Usually, a small quantity of fluid is first aspirated and examined by light microscope to observe for the presence of viable protoscolices. If they are present, the cyst is aspirated completely.
  • At this point, exclude possible connections of the cyst with the biliary tree by means of injection of contrast medium in the cavity. If no connections are evident, a scolecoidal agent, usually hypertonic sodium chloride solution or ethanol, is injected and left for a variable period (usually 5-30 min) and then reaspirated. The destruction of protoscolices can be observed in fluid sample aspirated after the injection of a scolecoidal agent. This sequence is termed PAIR (puncture, aspiration, injection, reaspiration). As happens with drug therapy, positive responses include both a decrease in cyst size and a progressive change in echo pattern (generally solidification).
  • From a diagnostic standpoint, PAIR is the only method that helps provide a direct diagnosis of the parasitic nature of the cysts. Neither imaging modalities nor serology is sufficient to exclude the diagnosis. PAIR is also an effective alternative to chemotherapy alone because it has a higher efficacy and avoids the problem of drug resistance. It also shortens the time of treatment and final recovery. PAIR is a valuable alternative to surgery in terms of cost containment and hospitalization time. In types I and II (Gharbi classification), CE1 and CE3a (WHO-IWGE classification) echinococcal cysts with no or incomplete response to therapy, PAIR is an effective therapeutic tool in the management of human cystic echinococcosis.
  • Increasing evidence shows that CE2 cysts (multivesiculated, type I in Gharbi classification) tend to relapse after PAIR, so adopt other percutaneous treatments for this type of cyst.
  • Reserve PAIR for use in highly specialized centers where teams are well prepared to deal with possible complications.

Consultations

• Consult a surgeon to discuss the opportunity of surgical intervention.
• Consult a radiologist for injection of contrast medium in the cyst after fluid aspiration if PAIR is scheduled. Contrast injection in the cyst allows the physician to exclude connections of the cyst with the biliary tree. Contact of scolecoidal agents, such as alcohol and hypertonic sodium chloride solution, with the biliary epithelium may lead to cholangitis. Attempts to inject albendazole directly into the cysts have yielded interesting results in animal studies but are still methodologically weak in human studies. Most recently, a glucose solution as a scolecoidal agent has been used with good results in vitro.⁷ Studies in vivo should confirm the safety of this approach before it can be applied to humans.
• Consult an anesthesiologist for assistance in case of anaphylactic shock or anaphylactoid reactions if PAIR is scheduled.

Medication

Albendazole and mebendazole are the only anthelmintics effective against cystic echinococcosis. Albendazole is the drug of choice against this disease because its degree of systemic absorption and penetration into hydatid cysts is superior to that of mebendazole. Albendazole in combination with percutaneous aspiration or PAIR therapy can lead to a reduction in cyst size, and, in one study, it improved efficacy over albendazole alone against hepatic hydatid cysts.⁸ When surgery cannot be avoided, presurgical use of albendazole in echinococcus infestations reduced risk of recurrence and/or facilitated surgery by reducing intracystic pressure.

Treatment of echinococcosis for patients weighing more than 60 kg is albendazole administered PO with meals in a dose of 400 mg twice daily for 28 days. A dose of 15 mg/kg of body weight daily in 2 divided doses (not to exceed total daily dose of 800 mg) has been suggested for patients weighing less than 60 kg. For cystic echinococcosis, the 28-day course may be repeated after 14 days without treatment to a total of 3 treatment cycles.

Anthelmintics

Parasite biochemical pathways are sufficiently different from the human host to allow selective interference by chemotherapeutic agents in relatively small doses.

Albendazole (Albenza)

Decreases ATP production in worm, causing energy depletion, immobilization, and, finally, death. To avoid inflammatory response in CNS, patient must also take anticonvulsants and high-dose glucocorticoids.

Mebendazole (Vermox)

Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine where helminths dwell.

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