António Menezes da Silva*
General Surgeon; President of the World Association of Echinococcosis, Member of the Directive Council of the Portuguese College of General Surgery, Portugal
Received: 10 October, 2015; Accepted: 26 October, 2015; Published: 28 October, 2015
António Menezes da Silva, General Surgeon, Estrada da Luz, 59 – 8º. Dto. – 1600-152 – Lisboa – Portugal, Tel: + 351 919 851 695; E-mail:
da Silva AM (2015) Cystic Echinococcosis in the Liver: Nomenclature and Surgical Procedures. J Surg Surgical Res 1(3): 059-065. 10.17352/2455-2968.000015
© 2015 da Silva AM. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Cystic Echinococcosis; Hydatid Cyst; Cyst sterilization; Hydatidectomy; Cystectomy
Cystic Echinococcosis (CE) is a zoonotic infection caused by larval form of the parasite Echinococcus granulosus. The adult tapeworm inhabit the small intestine of some carnivores (called definitive or final hosts), and the larval phase, or “metacestode” develops in the herbivores (intermediate hosts). The presentation form of the larval phase is the development of cysts, called hydatid cysts. Although all of us know the vital cycle of the parasite and the different aspects of the disease, the designations around the parasite, its evolution and some therapeutic procedures is not uniform. In fact we frequently see the use of inappropriate terms, based on incorrect concepts. It would be useful to use the same nomenclature and it is absolutely necessary that the nomenclature is correct and universally accepted. So, it is pertinent to remember some important points related to the CE and, above all, to clarify some aspects concerning its nomenclature, in order to understand better the therapeutic options, particularly the different surgical approaches.
Despite the cysts can be localized in any organ, liver localization is the most frequent (60-70%). The development of a hydatid cyst is slow and usually without specific clinical manifestations, so the diversity of clinical manifestations is related to the anatomical localization of the cyst, its dimension, and the antigens responsible for the systemic hypersensitivity, which can occur in sequence of cyst rupture, spontaneously or traumatic, resulting in secondary echinococcosis. The therapeutic approach has nowadays different possibilities, which will be referred in this manuscript.
Human Echinococcosis is a zoonotic infection caused by larval forms (metacestodes) of tapeworms of the genus Echinococcus. Although there are different species of Echinococcus, only five of them – E. granulosus, E. multilocularis, E. oligarthrus, E. vogeli and E. shiquicus – are formally recognized currently as taxonomically relevant. To distinguish the diseases caused by these different species, the World Health Organization (WHO) proposed the designation Cystic Echinococcosis (CE) for the disease caused by E. granulosus, Alveolar Echinococcosis (AE) for the disease caused by E. multilocularis, and Polycystic Echinococcosis (PE) for the disease caused either by E. vogeli and E. oligarthus. No human cases due to E. shiquicus have ever been observed.
Cystic Echinococcosis is the most frequent of them. Actually E. granulosus is not the sole specie causing CE: the genotypes G1-G3 are now grouped as E. granulosus sensu stricto, G4 as E. equinus, G5 as E. ortleppi, G6-G10 as E. canadensis and the ‘lion strain’ as E. felidis. Among these strains, E. granulosus sensu stricto has a broad geographical distribution with a wide host range and is the major causative agent of human CE, but E. canadensis has also been identified in humans in many areas of Europe and other regions too.
In the E. granulosus vital cycle we consider the adult tapeworm, which lives in the intestine of some carnivores (called definitive or final hosts), and the larval phase, or “metacestode”, which develops in the herbivores (intermediate hosts). The intermediate hosts, in which humans are included, are infected by ingestion of eggs within the feces of the definitive hosts. Following ingestion of eggs the oncosphere, by lytic secretions, goes through the intestinal mucosa and into the host circulatory system (venous and lymphatic) and reaches one organ, where cystic development begins. This process involves degeneration of the oncospheral stage and emergence of the metacestode stage. The larvae change into a typical “bladder” (vesicle) with a germinal layer, called hydatid cyst, which is the presentation form of the disease in the intermediate hosts. This was other designation for CE in the past, and this is the reason why it was also referred as hydatid disease. However, this designation was also used to designate the other forms of Echinococcosis (Alveolar, Polycystic, etc.), which is wrong. All of us have frequently noticed, in published articles and in communications during scientific meetings, and also in WHO publications, to call hydatid diseases to the different forms of Echinococcosis. That is unacceptable, and it is time to finish the incorrect use of this terminology!
The parasite or “hydatid”
In primary CE the metacestodes (hydatid cysts) develop in various sites from oncospheres after ingestion of E. granulosus eggs. The eggs of these tapeworms excreted by carnivores may infect various species of natural intermediate host animals and humans, and may develop in almost any organ. Most patients (up to 80%) have a single organ involved and harbour a solitary cyst, localized in approximately two-thirds of cases in the liver and in about 20% in the lungs.
In secondary CE the larval tissue spreads from the primary site , and proliferates after spontaneous or trauma-induced cyst rupture or after release of viable parasite material during invasive treatment procedures.
The hydatid cyst (Figure 1) is composed of two parts: the echinococcal parasite (or “hydatid”) and the “adventitia” that surrounds it, as Dévé defined it in the beginning of the last century , and there is no reason or legitimacy to modify this definition. “Hydatid” is the larval form of the tapeworms of the genus Echinococcus granulosus only.
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