Hippocrates recognized human hydatid over 2,000 years ago. The Arab
physician, Al Rhazes, made reference to hydatid disease of the liver in AD
Liver hydatid disease is a zoonosis caused by caused by larva of the dog
tapeworm, Echinococcus granulosus, with man acting as an accidental
Liver hydatidosis is characterized by progressive growth of the hydatid
cyst, which in its mature form is a fluid filled cavity, delimited by an
external dense host fibrous reaction (pericyst) and two internal parasite
derived layers (endocyst). The hydatid cyst grows slowly and remains
asysmptomatic for many years. Symptoms arise only when the cyst has
grown large enough to cause the pressure on adjacent organs or when a
complications occurs. Infection and intrabiliary rupture are the most
Causative Agent Intermediate host Final host
Echinococcus granulosus Sheep, Human dog
Echinococcus vogeli Paca dog, fox
Echinococcus multilocurlaris Rodents dog,fox,
Echinococcus oligarthrus ? Human dog, fox
In E. multilocularis infestation the germinal layer of the cyst sends out
processes Into the surrounding host tissue which in turn form fluid filled
pockets containg proto-Scolices.The germinal layer continues to spread
and multiply like a cancer,therefore It carries mortality upto 50%.
E.vogeli infestation is very rare and found occasionally in Brazil.Paca a
wild Rodent is the intermediate host and final host is the hunting or
It is world wide in distribution and is endemic in many countries like
Mediterranean area, the Middle East and South America. In India it is
found in the northern states.
The adult form of Echinococcus granulosus resides in the small intestine
of dogs. The ova from the adult worm are shed through the canine feces
into the environment, where the intermediate host sheep and humans
ingest the eggs, in humans after entering proximal portion of the small
intestine, the larvae burrow through the mucosa, enter the portal
circulation and travel to liver. The cycle is completed when dogs eat the
carcass of animals infected with the hydatid cysts.
A primary cyst in the liver is composed of three layers:
1. Adventitia (psuedocyst / pericyst) – consisting of compressed
liver parenchyma and fibrous tissue induced by the expanding parasitic
2. Laminated membrane (ectocyst) – is elastic white covering, easily
separable from the adventitia.
3. Germinal epithelium (endocyst) – is a single layer of cells lining
the inner aspects of the cyst and is the only living component, being
responsible for the formation of the other layers as well as the hydatid
fluid and brood capsules within the cyst. In some primary cysts laminated
membranes may eventually disintegrate and the brood capsules are freed
and grow into daughter cysts. Sometimes the germinal Epithelium
protrudes out towards the external side of the cyst, to form exogenous
daughter cysts, which if left untreated may cause recurrence.
The Hydatid cysts are slow growing approx 2 – 3 cm / year and remain
inapparent for long time.
Patients with simple or uncomplicated multivesicular or univesicular cysts
are asymptomatic. When symptoms occurs they are caused by pressure
on the adjacent organs. Abdominal pain and tenderness are the most
common complaints followed by palpable mass. Jaundice and ascites are
uncommon. With secondary infection tender hepatomegaly, chills, and
spiking temperatures occurs. Urticaria and erythema occur in cases of
generalized anaphylactic reaction. With biliary rupture the classic triad of
jaundice, biliary colic and urticaria occurs.
COMPLICATIONS OF HYDATID CYST
Intrabiliary rupture of Hydatid cyst
When ruptured in to biliary tree, hydatid cysts commonly manifest with
findings of biliary obstruction and cholangitis. The presence of dilated
common bile duct, jaundice, or both in addition to a cystic lesion of liver is
strongly suggestive of a hydatid cyst with intrabiliary rupture. This
complication can be most specifically diagnosed by ERCP or PTC.
( because of risk of intraperitoneal rupture of the hydatid cyst which may
result in peritoneal dissemination and anaphylactic reactions because of
the spillage of the highly antigenic cyst fluid PTC is contraindicated in
hydatid disease of liver). The presence of intrabiliary rupture requires
exploration and drainage of the biliary tract. During the exploration the
biliary tree is cleared of any hydatid material which is confirmed by intra-
operative choliangiography or choledochoscopy. After evacuation of
hydatid elements from the biliary tree, either side to side
choledochoduodenostomy or external T-tube drainage is done.
Suppuration of cysts takes place in 5 to 15 % of cases. The clinical picture
resembles liver abscess and urgent surgery is necessary.
Incidence of recurrence is estimated to range from 8.5 % to 25 %. The
causes of recurrence are peritoneal spillage and implantation during
operations. New cyst formation from exogenous vesicles attached to the
remaining pericyst after conservative treatment and reinfection.
Cholelithiasis exists with liver hydatid in three forms: true hydatid lithiasis,
parahydatid lithiasis and accidential coincidence. In true hydatid lithiasis,
histologic examination reveals the presence in central part of the stones of
hydatid elements that constitute the lithogenic nidus. The parahydatic
lithiasis is attributed to the abnormal delay in passage of bile into
gallbladder provoked by an adjacent hydatid cyst.
Routine laboratory tests are rarely abnormal occasionally eosinophilia
may be present. Serum alkaline phosphatase levels are raised in one third
Serological tests detect specific antibodies to the parasite and are the
most commonly employed tools to diagnose past and recent infection with
E. granulosus. Detection of IgG antibodies implies exposure to the
parasite, while in active infection high titres of specific IgM and IgA
antibodies are observed. Detection of circulating hydatid antigen in the
serum is of use in monitoring after surgery and pharmcotherapy and in
prognosis. ELISA is used most commonly, but alternate techniques are
counter-immuno-electrophoresis and bacterial co-agglutination. Elisa
techniques have a high sensitivity above 90% and are useful in mass
scale screening. The counter-immuno-electrophoresis has highest
specificity (100%)and high sensitivity (80 – 90%).
It has been used most frequently in the past but this cutaneous
hypersensitivity reaction using hydatid fluid is at present considered only
of historical importance. The allergen is rarely standardized and
infestation with other helminthes particularly cestodes can give a false
Plain abdominal radiography may reveal calcification, hepatomegaly, or
indirect evidence of an hepatic SOL. (for eg. Elevated hemi diaphragm,
right lung basal collapse, and pleural effusion). A coincidental lung cyst
may be picked up on a plain skiagram.
Ultrasound – is currently the primary diagnostic technique and has
diagnostic accuracy of 90%. Findings usually seen are:
a) Solitary Cyst – anechoic univesicular cyst with well defined
borders and enhancement of back wall echoes in a manner similar to
simple or congenital cysts. Features are suggesting a hydatid etiology
include dependent debris (hydatid sand) moving freely with change in
position; presence of wall calcification or localized thickening in the wall
corresponding to early daughter cysts.
b) Separation of membranes (ultrasonic water lily sign) due to
collapse of germinal layer seen as an undulating linear collection of
c) Daughter cysts - probably the most characteristic sign with cysts
within a cyst, producing a cartwheel or honeycomb cyst.
d) Multiple cysts with normal intervening parenchyma (differential
diagnosis are necrotic secondaries, Polycystic liver disease, abscess,
chronic hematoma and biliary cysts.
e) Complications may be evident such as echogenic cyst in infection
or signs of biliary obstruction usually implying a biliary communication.
Gharbi Classification on ultrasonographic features of Hydatid Cyst3
Type Ultrasound Appearance
I Pure fluid Collection
II Fluid collection with a split wall
III Fluid collection with septa
IV Heterogeneous echo pattern
V Reflecting walls
Type V cysts determined by ultrasound to be calcified and have been
assumed to be dead cysts and do not require surgery.
Computed Tomographic scan - has the highest sensitivity of imaging of
the cyst (100%). It is the best mode to detect the number, size, and
location, of the cysts. It may provide clue to presence of complications
such as infection, and intrabiliary rupture. CT features include sharply
marginated single or multiple rounded cysts of fluid density (3 – 30
Hounsfield units) with a thin dense rim.
Angiography – of the liver is suggestive but due to lack of specificity and
availability of lesser invasive techniques it is rarely required. It may be
required in a differential diagnosis of suspected malignancy or vascular
malformation. Typical features include an avascular lesion with vascular
displacement and a thin peripheral halo of higher density.
Direct cholangiography – (Endoscopic or percutaneous) may be
required in suspected intrabiliary rupture and bile duct obstruction. ERCP
is also a valuable method for detecting post-operative complications
involving the biliary tree following surgical intervention.
Radionuclide scan – has largely replaced by ultrasound and CT scan. It
remains most accurate method of demonstration of a bronchobiliary
Immunoscintigraphy – is an innovation using radiolabelled antibodies to
antigens in the parasite.
Magnetic resonance Imaging (MRI scan) – MRI delineates the cyst
capsule better than CT scan, as a low intensity on both T1 and T2
weighted images. However CT scan is better in demonstration of mural
calcifications, cysts less than 3 cm may not show any specific features
and small peritoneal cysts may be missed.
Hydatid was considered to be a contraindication for FNAC. However, it
may be used in diagnosis of hydatidosis if radiological studies reveal a
cyst and serological tests are equivocal. Diagnostic features include
presence of laminated membrane, which gives a positive periodic acid
schiff reaction, and a diagnosis of hydatid may be presumed.
The treatment of choice is surgery. The principle of hydatid surgery are 1)
Total removal of all infective components of the cysts; 2) the avoidance of
spillage of cyst contents at time of surgery; 3) management of
communication between cyst and adjacent structures; 4) management of
the residual cavity; 5) minimize risks of operation7,8.
All the surgical procedures can be divided into two large groups,
conservative group and radical group. The conservative technique
consists of aspiration of the cyst, instillation of scolicidal agents and
evacuation of the cyst contents and leaving the pericyst. The residual
pericyst is managed by marsupialization, which consists of suturing the
edges of opened pericyst with the skin, capitonnage (suture obliteration),
partial pericystectomy, omentoplasty (omentum is thought of fill residual
cavity, to assist healing of raw surfaces and to promoted resorption of
serosal fluid and macrophagic migration of septic focus)10, and suture
closure of the pericyst cavity after filling it with saline.
Intracystic injections of scolicidal agents used in the past are
formaldehyde solution, cetrimide solution 0.5%, hypertonic saline solution,
0.5% silver nitrate solution, and hydrogen peroxide solution. The
arguments against the use of conventional intracystic solutions are:
1. In a large univesicular cyst, dilution of the scolicidal solution is
unpredictable and impairs its efficacy.
2. If cyst communicates with the biliary system, it can lead to serious
complications like sclerosing cholangitis and acute pancreatitis, have
been reported with use of formaldehyde and hypertonic saline. Air
embolism has been reported with the use of hydrogen peroxide.
3. Cetrimide solution produces severe adhesions formation.
The best choice is silver nitrate solution 0.5% which has been reported to
be safe and efficacious.
The conservative surgical procedures are easy to perform but the
postoperative complications and duration of hospital stay are not
Radical surgical procedures include cystectomy, pericystectomy,
lobectomy and hepatectomy Radical procedures have lower rate of
complications and recurrences but many authors consider them
inappropriate, claiming that intraoperative risks are too high for a benign
Cystectomy – The procedure of choice is cystectomy. The procedure
involves removal of hydatid cyst, comprising laminar layer, germinal layer
and cyst contents i.e. daughter cysts and brood capsules. No attempt is
made to remove the pericyst. The procedure is simple to perform and has
low recurrence rates.
Pericystectomy – this procedure involves non-anatomical resection of
cyst and surrounding compressed liver tissue. This is technically more
difficult procedure than cystectomy and can be associated with
considerable blood loss; it can also be hazardous in the case of large and
complicated cysts when the cyst distorts vital anatomical structures.
Hepatic resections – is the only surgical therapy for E. multilocularis as
the disease is infiltrative and disease margin is ill defined. The arguments
against hepatic resection as a primary modality of treatment are that
outside of dedicated liver units there is considerable morbidity and
mortality from resection of what is essentially a benign condition and also
distortion of anatomy makes surgery more difficult.
LAPAROSCOPIC MANAGEMENT OF HYDATID CYSTS
A special instrument has been developed for the removal of the hydatid
cyst with the laparoscope called the perforator-grinder-aspirator
apparatus. The instrument penetrates the cyst, grinds the particulate
matter and sucks it all out. The advantage of this instrument over that of
conventional suction apparatus is that it does not gets blocked by the
daughter cysts and laminated membranes. Vacuum obliteration of cavity
is carried out with application of – 250 mbar of negative pressure, which
obliterates the cystic cavity by clinging to the opposing cyst walls9.
COMPLICATIONS OF SURGERY
Biliary leakage is the most frequent postoperative complication following
surgery for hydatid of liver. It has been reported to occur in about 50% of
cases because of the small-undetected communication between the cyst
and the bile ducts.
The surgical management of hydatid disease of liver carries a mortality
rate of 0.9 to 3.6 % and recurrence up to 11.3 % within 5 years.
Operations carry a progressively higher mortality – increasing from 6 %
after second to 20% after third1.
PERCUTANEOUS DRAINAGE OF HYDATID CYST
Puncture of hydatid cysts have been discouraged in the past due to the
potential risk of Anaphylactic shock and peritoneal dissemination.
However, in the recent years percutaneous drainage has been used
successfully to treat the hepatic hydatid cysts. Khuroo et al from India
reported 88% disappearance of cysts with percutaneous drainage which
was preceded by Albendazole therapy (10 mg/kg body weight) for 8
ENDOSCOPIC MANAGEMENT OF HYDATID CYST
The ERCP is effective in diagnosing biliary tree involvement from the cyst.
The Endoscopic management is useful in presence of intrabiliary rupture,
which requires exploration and drainage of the biliary tract and also after
surgery in presence of residual hydatid material (membranes and
daughter cyst) left in biliary tree. During the endoscopic exploration the
biliary tree is cleared of any hydatid material with a balloon catheter or a
dormia basket. The endoscopic sphinterotomy is also performed to
facilitate drainage of the common bile duct.
CHEMOTHERAPY FOR HYDATID DISEASE OF LIVER
The compounds in clinical use are the benzimidazole derivatives
(mebendazole and albendazole), which inhibit the uptake of glucose by
the parasite and inhibit production of adenosine triphosphate,
isoquinolone compounds (praziquantel) and immunostimulatory
compounds: isoprinosine and trans-2- phenoxycyclohexonol ethers
was the first drug to show any activity against hydatid cysts. It inhibits
glucose uptake in susceptible parasites resulting in depletion of the worms
energy sources and slow death. Its disadvantages are that it is poorly
absorbed from the gastrointestinal tract. Although progressively higher
doses for long periods have been given in an attempt to boost plasma
concentrations, it has resulted in a plethora of side effects like prolonged
fever, major liver disturbance, bone marrow depression and
glomerulonephritis. It is no longer used in hydatid disease.
The principal metabolite, albendazole sulfoxide has antihelminthic activity
over a half-life of 8.5 hours. A dose of 10 mg/kg/day achieves an intra cyst
concentration in excess of 100 ng/ml, which is within the effective
scolicidal range. Albendazole is administered in a dose of 10 – 15
mg/kg/day in adults or a fixed dose of 400 mg twice daily. The treatment is
given in cycles of 28 days with two weeks treatment free periods between
the cycles. The different schedules for the treatment are:
1. Inoperable cases - as primary treatment - 3 cycles
2. Pre-operatively – to reduce the risk of recurrence 6 weeks
3. Post-operatively to prevent recurrence in cases of intraoperative
cyst spillage – 3 cycles.
Cure is defined as disappearance of the cyst, improvement is defined as
> 25% reduction is size of cyst, membrane separation and appearance of
calcification and deterioration as an increase in cyst size. As reported in
study by Horton et al2 on 253 patients, cure rate was 32%, improvement
was seen in 43%, 21% had no response and 1.5% patients showed
increase in size of cyst.
Side effects of Albendazole therapy are: mild abdominal pain, nausea,
vomiting, pruritis, dizziness, alopecia, rash and headache. Occasionally
leucopoenia, eosinophillia, icterus, and mild elevation in transaminase
levels is seen.
increases the permeability of plasma membrane to calcium ions resulting
in rapid loss and extreme contraction and paralysis of worms. Oral dose
of 50 mg/kg/day for upto two weeks shows rapid scolicidal activity. Side
effects are mild headache, dizziness, drowsiness, abdominal pain, and
nausea. WHO has recommended the use of praziquantel preoperatively
to achieve the sterilization of the cysts or postoperatively in cases of cyst
rupture and spillage.
Isoprinosine is an immunomodulatory drug, which appears to act via
cytolytic effects on the cellular elements of the germinal layer, While the
persisting superficial structures prevent the dissemination of viable cells.
The drug has shown efficacy against E. granulosus and E. multilocularis
in an animal model.
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