ANNALS OF CLINICAL AND LABORATORY SCIENCE, Vol. 20, No. 6Copyright © 1990, Institute for Clinical Science, Inc.

Echinococcal Cyst of the Liver: Diagnosis and Surgical Management*

PETER M. FARMER, M .D .,t S. CHATTERLEY, M .D .,ta n d N . SPIER, M .D .$

Departments o f Pathologyf and Surgery,t North Shore University Hospital,

Cornell University Medical College Manhasset, NY 11030

ABSTRACT

The encysted larval form of Echinococcus granulosus may infest man as an incidental host. The liver is the organ most commonly involved, but the lung and brain may be affected. The disease is endemic where sheep are raised with dogs in a pastoral environm ent. Areas of high endemicity exist in rural North America. Human echinococcal disease is now seen in urban medical centers because of the changing patterns of migration and immi­gration. An echinococcal cyst of the liver is reported in a resident of the New York City m etropolitan area. Details of the life cycle, pathology, diagnostic imaging techniques and surgical management of hydatid cysts are reviewed.

Introduction

Echinococcal d isease in hum ans is usually caused by infestation of tissues by the encysted larva of the tapeworm Echinococcus granulosus. Adult tape­worms live in the jejunum of dogs which are the definitive hosts. In the usual life cycle, eggs are excreted in dog’s feces and are ingested by sheep. After the eggs hatch in the duodenum, the larvae m igrate to the sheep ’s viscera w here they becom e encysted . The cycle is com pleted when dogs are fed contami­nated viscera. Man becomes an inciden-

Address reprin t requests to: Peter M. Farmer, M .D., Departm ent of Pathology, North Shore Uni­versity Hospital, 300 Community Drive, Manhasset, NY 11030.

tal host by exposure to dogs and inges­tio n o f th e eggs. S ix ty p e rc e n t of echinococcal infections in man involve the liver as “hydatid cysts ”, but pulm o­n ary and b ra in in fe s ta tio n a re w ell known.14

The disease enjoys a worldwide distri­b u tio n b u t is typ ically found w h ere sheep are grazed and herded with the aid of dogs. Endem ic pockets of echino­coccosis are present in Canada and the U nited States, notably in shepherd com­munities in Utah and California. Occa­sional cases are e n c o u n te re d in th e Southeastern United States where back­yard pig keeping is prevalent.15

The migration of peoples from rural areas to urban centers has made echino­coccal disease a much more cosmopoli­tan m edical problem , and the overall

3850091-7370/90/1100-0385 $01.20 © Institute for Clinical Science, Inc.

386 FARMER, CHATTERLEY, AND SPIER

incidence appears to be increasing .9 Cases of echinococcal cysts have been recently rep o rted from large m edical centers in M assachusetts,3 Connecticut,8 and New York.15 It is im portant that phy­sicians in non-endemic areas be alert to the possibility of echinococcal disease. In­appropriate needle aspiration or open b iopsy could lead to sp illage of th e cyst contents and catastrophic dissemi­nation of the parasites.6 Surgical excision or evacuation of larval cysts is the only effective treatm ent.13 Surgery should be perform ed after a thorough pre-opera­tive evaluation and anticipation of poten­tial intra-operative complications. This communication reports on echinococcal cyst of the liver in a resident of the New York C ity m e t r o p o l i ta n a re a a n d describes its radiographic evaluation and the details of its surgical extirpation.

Case Report

A 29-year-old landscaper was admitted to North Shore University Hospital for evaluation of recurrent epigastric pain. He was born in Calabria, Italy and lived in a rural community near the town of Catan- zaro. An older sister had a history of an echinococcal cyst. The patient immigrated to the United States in 1980. For seven years he experienced bouts of pro­gressively severe right upper quadrant pain radiating to the back. Two years ago these episodes became associated with transient jaundice and sometimes with urticaria and arthralgias. These symptoms had been interpreted as owing to peptic ulcer disease or viral hepatitis. There was no history of change in bowel habits, vomiting, weight loss, fever, chills, or alcohol abuse. On admission to the hospital, the physical examination was unremarkable. The liver was non-tender and not palpably enlarged. Labora­tory evaluation included a normal hemogram with no eosinophilia. Serum bilirubin, alkaline phosphatase and transaminases were all within normal limits. Chest x-ray was normal. Computed tomography of the abdomen revealed a 6.9 x 5.5 cm cystic mass in the left lobe of the liver. The lesion contained septa- tions and interval rounded structures with features of daughter cysts. The multiseptated cyst could also be dem onstrated by abdom inal sonograms. Celiac/ hepatic angiography showed an area of hypovascular- ity in the left lobe of the liver with splaying of the middle hepatic artery.

At the time of laporotomy, the cyst was seen to replace the lateral segment of the left hepatic lobe and was attached to adjacent structures by multiple fibrous adhesions. The mass extended to the right of

the falciform ligament and beyond the ideal plane of resection, this contraindicating resection by left lat­eral segmentectomy. It was therefore elected to pro­ceed with evacuation and sterilization as the treat­ment of choice. Great care was taken to isolate the presenting surface of the cyst from all surrounding viscera by the placem ent of saline moistened lap pads. The contents were then aspirated and noted not to be purulent or bile stained. Thereupon the lesion could be separated into a fibrous pericyst and a collapsed endocyst. The latter was then removed with multiple daughter cyst and brood capsules. The remaining pericyst cavity was then irrigated with a 10 percent saline solution.

After a complete change of instruments, gloves, and local drapes, a portion of omentum was brought into the pericyst cavity and sutured in place to main­tain its position. The gallbladder and common duct were carefully inspected and noted to be unremark­able. It was decided not to proceed with cholan­giography or cholecystectomy and common duct exploration, since the patient had normal liver func­tion tests, and imaging studies had not revealed any hydatic debris within the biliary tree. The incision was sutured after insertion of closed suction Jackson- Pratt drains. The patient had an uncomplicated post­operative course. The incisional drains were gradu­ally shortened and removed, and the patient was discharged on the 18th post-operative day. Two years following surgery, the patient enjoys good health and has no evidence of recurrent hydatid disease.

Microscopic examination of the parasitic ectocyst revealed a multilaminated hyaline cuticular mem­brane which assumed a curvilinear shape because of its elastic properties (figure 1). Also identified was an inner germinal layer or endocyst containing multiple protoscolices including invaginated heads with suckers and hooklets (figure 2). In addition, frag­ments consisting of calcareous corpuscles mixed with disrupted hooklets were present, characteristic of “hydatid sand” (figure 3).

Discussion

E p id e m io l o g y

Echinococcal disease was evidently known to H ippocrates who described water filled cysts in the livers of infested patients. The w ord “echinococcus” is d e r iv e d from th e G re e k , m ea n in g “hedge hog berry”.8 The term “hydatid” re fe rs to i ts w a te ry c o n te n ts . T he disease is still endemic in Greece as well as o th e r M e d ite r r a n e a n c o u n tr ie s including Italy and Turkey.13 Areas of extensive infestation include the Yukon territory where up to 40 percent of the native population harbor the parasite.8

ECHINOCOCCAL CYST OF THE LIVER 387

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mM i

F ig u r e 1. Cyst wall. The thin germinal layer or endocyst at the top of the illustration is separated from the laminated thicker ectocyst by a hyaline zone. The elastic properties of the cyst created a corrugated appearance. (H&E x 100)

High endemicity is also found in the Tur- kano district of Kenya where the visible prevalence is 10 to 15 p e rc e n t.14 The definitive hosts of Echinococcus granu­losus are sylvatic carn ivores such as wolves, dogs, and foxes.8 The secondary hosts vary with the geographic location and in c lu d e sh eep , goats, donkeys, camels, some kangaroos, moose, and car­ibou.614 It is alleged that the parasite was in troduced into U tah by the im ­p o r ta t io n o f sh e e p and dogs from Australia.16

Pa t h o l o g y

In response to the host larvae, the host tissues produce a rigid fibrous cap­sule or pericyst. This is usually not found in surgical specimens except where exci­sion and segmentectomy are performed.

The exocyst is an elastic acellular layer elaborated by the parasite. It is perm e­able to nutrients from the hosts, but not to bacterial organisms.15 The endocyst or inner m em brane is a germ inal layer which protrudes into the cyst cavity and forms m ultip le vescicu lar s tru c tu re s known as brood capsules.7 The la tter contain protoscolices which float in the highly antigenic cyst fluid or “eau de roche”.8 Protoscolices have a head invag- in a ted from the endocyst w ith four suckers and a rostellum with two rows of hooklets.15

Under certain circumstances, perhaps in response to a th reat to the larvum, multiple septations form, leading to the formation of “daughter cysts.” Alterna­tively, it has been suggested that the production of daughter cysts may be part of a natural aging process.7 Brood cap­

388 FARMER, CHATTERLEY, AND SPIER

F ig u r e 2. Brood capsu les. T h ree b rood capsu les a re illu s tra ted . E ach con ta ins m u ltip le p ro tosco lices and is su rro u n d e d by a layer of g erm inal layer. (H & E X 100)

sules and protoscolices that break away from the germ inal layer form “hydatid sand” which settles at the dep en d en t portions of the cyst.7 Mural calcification occurs in up to 10 p e rcen t of cy sts .8 D ensely calcified cysts contain dead organisms and are usually asymptomatic.

C l in ic a l F e a t u r e s

Hydatid or endinococcal cysts of the liver are slow growing and often unrec­ognized until quite large. The usual p re­senting symptoms are abdominal distress and a right upper quadrant mass.8 Jaun­dice and allergic phenomena with rash and arthralgias are rare,6 but they were p resen t in the patien t in this report. Cysts may present with dramatic compli­cations. R upture into the biliary tree occurs in five to 10 percent of hepatic echinococcal cysts and may mimic acute cholecystitis or choledocolithiasis.10 The diagnosis is then confirmed by the dem ­onstration of daughter cysts or protosco­

lices in the stool or vomitus. Rupture into the abdominal cavity may result in peritonitis and metastatic seeding of the organisms. Extension through the dome of the liver will produce a subdiaphrag- matic abscess. If intrathoracic evolution and bronchial erosion occur, patients cough up brood capsules and other cyst contents and may ultimately develop a bronchobiliary fistula.1,4 Vascular access by the highly antigenic fluid occasionally results in anaphylaxis and death. Sec­ondary pyogenic infection of a cyst can lead to liver and lung abscess.14

D ia g n o s is

S ev e ra l im ag ing m o d a litie s have proved useful in the detection of para­sitic cysts. Plain x-rays may demonstrate an “ e g g s h e l l” p a t te rn in c a lc if ied lesions.2 Ruptured cysts may contain an air flu id level, or a m eniscus may be seen consisting of the membranes float­ing on the surface of the residual fluid.

ECHINOCOCCAL CYST O F THE LIVER 389

F ig u r e 3. H y d a tid sand. F ra g m en ts o f hook le ts an d calcareous co rpuscles from d e g e n e ra te d p ro tosco lices form “h y d a tid sa n d ” w hich m ay b e an im p o rta n t c lue in diagnosis. (H & E x 250, in d ire c t illum ina tion)

The latter finding, referred to as a “water lily ” sign, may also be d e te c te d by abdom inal sonography .7 R olling the patient to dispense the hydatid sand and increase echogenicity of the cyst con­tents also creates a characteristic sono­graphic pattern. Com puted tomography is the most effective imaging technique available for the diagnosis of hydatid dis­ease. It is highly sensitive and specific and is able to demonstrate cyst margins as w ell as m u ltilo cu la rity and o th e r u n ique featu res of echinococcal d is­ease .2,6 H epatobiliary scanning using 99mTc has been a helpful diagnostic aid, bu t can produce a pa tte rn m im icking calculous cholecystitis and should not be relied upon for diagnosis.1,10 Angiogra­phy is rese rv ed for situations w here resection is anticipated and knowledge of

th e v ascu la r ana tom y is im p o rta n t. Recently, magnetic resonance imaging in the diagnosis of hydatid disease has been reported .15

Immunologic techniques for the diag­nosis of echinococcus have advanced in recen t years. The Casoni test, rarely used today, consists of injecting human and animal hydatic fluid into the dermis of suspected patients. The test has sev­eral drawbacks. In addition to its lack of sensitivity and specificity, the test itself may sensitize the patient or produce ana­phylaxis in an already sensitized host. Casoni testing has been abandoned in m ost developed c o u n tr ie s .17 In d irec t hem agglutination and enzym e linked immunosorbent assay have proved more satisfactory and are generally in use to d ay .15 T hey are espec ia lly he lp fu l

390 FARMER, CHATTERLEY, AND SPIER

when imaging studies are inadequate to distinguish hydatid cysts of the liver from pyogenic abscesses, o ther para­sites, or neoplasms.

T r e a t m e n t

Surgery is the therapeutic mainstay of hydatid disease, although the choice of procedure has been the subject of some controversy. External or internal drain­age, capitonnage, omentoplasty, cystec­tomy, and partia l hepa tec tom y have been recom m ended.613 There is general agreem ent that certain principles must be observed.16 First, spillage of the cyst conten ts m ust be avoided. Secondly, adequate drainage of the cyst cavity must be accomplished. Percutaneous aspira­tion o f su spec ted echinococcus cysts should not be performed because of the risk of dissem ination and anaphylaxis.8 M arsupialization and external drainage have been largely abandoned because of a high incidence of post-operative infec­tion and occasional m ortality.61316 For cysts which are m ulticentric within one anatomic unit of the liver, partial hepatic lobectomy or segmentectomy have been advocated.11 It is recom m ended that this technique be reserved for lesions which are peripherally located, especially in the left lateral segments and for pedun­c u la ted cysts. M ajor liv e r rese c tio n should be avoided.

The m ost popular techn ique is cyst evacuation. This requ ires m eticulous isolation of the lesion to avoid spillage. Use of a cryogenic cone to seal off the cyst has been advocated by Saidi.12 After rem oval of flu id , daughter cysts, and parasitic membranes, the cavity is irri­gated w ith scolicidal solution.16 Many agents have been used including chlor- hexidine, hydrogen peroxide, hypertonic saline, ethanol, cetrimide, silver nitrate, and the anti-helminthic drug, m ebenda­zole.8 Formalin has caused serious sys­tem ic reactions and fatalities, and its use

has been abandoned. The cyst cavity m ust be managed by deflating it with a system of closed vacuum drainage or by o b lite ra tio n v ia o m en to p la s ty . T his en h an ces liv e r re g e n e ra tio n , avoids infection, and minimilizes fistula forma­tion.16 Sclerosing agents should be used with great caution, since their entry into the biliary tree may result in obliteration of the hepatic ducts. This complication has necessitated partial hepatectom y and hepatojejunostomy.

Summary

The encysted larvae of Echinococcus granulosus may infect man as an inci­dental host. The liver is the most com­mon target organ, bu t brain and pulmo­nary involvem ent are known to occur. Echinococcal disease is endemic where sheep (the prim ary hosts) are herded by d o g s ( th e s e c o n d a ry h o s ts ) . M an becomes infected by ingesting the eggs after exposure to dog’s feces. Areas of high endem icity exist in ru ra l N orth America. Human echinococcal disease is also seen in urban medical centers as a result of changing patterns of migration and immigration. H ydatid cysts of the liver may mimic pyogenic abscesses or neoplasms. Abdominal com puted tomog­raphy and sonography are helpful in dis­tinguishing these lesions. Newly devel­oped serologic tests are also available. Surgery is the only effective treatm ent. Contamination of the abdominal organs by cyst contents m ust be avoided, and adequate postoperative drainage is nec­essary.

References

1. Ba k r o s , J. L .: Hydatid disease of the liver. Am. J. Surg. 135:597-600, 1978.

2. Beggs, I.: The radiology of hydatid disease. Am. J. Roentg. 745:639- 648, 1985.

3. Case records of the Massachusetts General Hos­p ita l. C ase 31-1980. New E ngl. J. M ed. 303:325-331, 1980.

4. HANKINS, J. R .: M anagement of complicated

ECHINOCOCCAL CYST O F THE LIVER 391

hepatic hydatid cysts. Ann. Surg. 158:1020- 1023, 1963.

5. J i d e i i a n , Y. : Hydatid disease surgery. 34:155- 158, 1953.

6. L a n g e r , J. C., R o s e , D. B., K e y s t o n e , J. S., T a y l o r , B. R ., and L a n g e r , B.: Diagnosis and management of hydatid disease of the liver. Ann. Surg. 199-,412-417, 1984.

7. L e w a l l , D. B . and M c C o r k e l l , S. J.: Hepatic echinococcal cysts; Sonographic appearance and classification. Radiology 155:773— 775, 1985.

8. L e w i s , J. W ., Koss, N . , and K e r s t e i n , M . D.: A review of echinococcal disease. Ann. Surg. 181:390-396, 1975.

9. M a t o s s i a n , R . M . , R i c k a r d , M . D ., and CYMTH, J. D.: Hydatidosis. A global problem of increasing im portance. Bull. World Health Organization 55:499-507, 1977.

10. N a g l e z , A . , E n a t , R., B r e n n e r , B . , I s r a e l ,O., and A r g o v e , S.: Hydatid cyst of the liver rupturing into the biliary tract mimicking acute cholecystitis on hepatobiliary scanning. Am. J. Gastroent. 80:819-921, 1985.

11. P i s s i o t i s , C . A., W a n d e r , J. V., and C o n d o n ,

R. E.: Surgical treatm ent of hydatid disease. Arch. Surg. 104:454- 458, 1972.

12. SAIDI, F. and NAZARIAN, I.: Surgical treatm ent of hydatic cysts by freezing of cyst wall and instal­lation of 0.5 percent silver nitrate solution. New Engl. J. Med. 284:1346-1348, 1971.

13. S a y e k , I., Ya l i n , R., and Sa n a c , Y .: Surgical treatm ent of hydatid disease of the liver. Arch. Surg. 115:847-850, 1980.

14. SU N , T.: Color Atlas and Textbook of Diagnostic Parasitology. New York, Igaku-shoin, 1988, chapter 46, p. 272-279.

15. S u n , T., Ra c k s o n , M., and F ä r b e r , B.: Current status of hydatid disease. Report of a case and review of the literature. Diag. Dis. 6:170—184,1988.

16. W e i r i c h , W. L .: Hydatid disease of the liver. Am. J. Surg. 138:805- 808, 1979.

17. Ya r z a b a l , L . A., S c h a n t z , P., and L o p e s - L e n e s , M. H.: Com parative sensitivity and specificity of the Casoni intradermal and the immunoelectrophoresis tests for the diagnosis of hydatid disease. Am. J. Trop. Med. H/G 24: 843-848, 1975.