HYDATID DISEASE

OF LIVER

Akriti Sah7th Semester

North DMC Medical College & Hindu Rao Hospital

Malka Ganj, Delhi 110007

Dated: 01/09/17

Among many liver infections, is

Hydatid disease which will be our

topic of discussion today.

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WHY DO WE NEED TO DISCUSS IT?

BURDEN

Globally distributed and found in every

continent except Antarctica. Very common

in countries around the Mediterranean

Sea.

More than 1 million people are affected at

any one time. (WHO)

AND IN INDIA

High incidence reported from Tamil Nadu,

Andhra Pradesh. Akriti Sah

Let me draw your

attention to the term:

ECHINOCOCCOSIS

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1.Human echinococcosis is a zoonotic disease that is

caused by parasites, namely tapeworms of the genus

Echinococcus.

2.Echinococcosis occurs in 4 forms:

3.The two most important forms, which are of medical and

public health relevance in humans are

4.Cystic echinococcosis (CE): also known as hydatid

disease or hydatidosis, caused by infection with the larval

stage of Echinococcus granulosus.

(most frequently observed form.)

5.Alveolar echinococcosis (AE): caused by infection with the

larval stage of E. multilocularis. (rare)

ETIOLOGY

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`

Common name of E. Granulosus:

Dog Tapeworm or Hydatid worm

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Echinococcus granulosus adult, stained

with carmine. Close-up of the scolex of

E. granulosus.

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LIFE CYCLE

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MODE OF INFECTION:

2. The most common mode of transmission to humans is

by the accidental consumption of soil, water, or food

that has been contaminated by the fecal matter of an

infected dog or by direct contact with an infected dog

(handling/ playing with infected dogs.)

3. Humans act as so-called accidental intermediate

hosts in the sense that they acquire infection in the

same way as other intermediate hosts, but are not

involved in transmitting the infection to the

definitive host.

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PATHOGENESIS

1. The ingested eggs release oncospheres that are able to

penetrate the human intestinal wall.

2. These oncospheres enter the radicles of portal vein and

are carried to the liver. The liver acts as the first filter where

60-70% of human infections are located.

3. Some embryos may pass through the hepatic capillaries

and enter the pulmonary circulation. Lungs act as the

second filter.

4. A few of these embryos may pass pulmonary circulation

and enter general circulation and may lodge in various

organs

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1. Wherever the embryos settle, an active cellular reaction consisting of

monocytes, giant cells and eosinophils takes place around the parasite.

2. A large no of parasites are thus destroyed by this host defence

mechanism.

3. Some however escape and develop into cysts. The cellular reaction in

the cases gradually disappears, followed by the appearance of fibroblasts

and the formation of new blood vessels.

4. Fibroblasts lay fibrous tissue, which envelops the growing embryo. This

is known as pericyst.

5. This pericyst merges with the surrounding normal tissue to provide

nutrition to the growing parasite.

6. In old cysts the pericyst may become sclerosed or calcified and parasite

within it may die.

Development of hydatid cyst in the organ

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The cyst wall secreted by the embryo consists of 2

layers

ECTOCYST

ENDOCYST

PERICYST- blood vessels

and fibroblasts

clear colorless or pale yellow . Antigenic and hence used for Casoni Test (immediate hypersensitivity skin test, many false p

Acellular, laminated,

hyaline layer

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1. Cysts most often occur in the liver (70%) or

lungs (20%). However, 10% of cysts can be

found anywhere in the body, including the spleen

(6%), heart (2%), kidney (2%), and brain (< 2%).

2. Cysts are usually unilocular, and can range

anywhere from 1 cm to 15 cm in diameter. They

also tend to affect the right lobe more frequently

than the left lobe due to the nature of portal

blood flow.

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SYMPTOMS

1. It can go undetected for many years due to

i. the slow growth and development of cysts and

ii.the response of the host’s immune system.

2. Depending on the size and location, cysts can eventually exert pressure

on nearby structures, producing discomfort, pain, nausea and vomiting.

3. Cysts in the liver can compress bile ducts, causing obstruction that can

manifest as obstructive jaundice,

abdominal pain,

anorexia, and

pruritus.

4.When in the lungs, cysts can irritate the membranes leading to chronic

cough, dyspnea, pleuritic chest pain, and hemoptysis.

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COMPLICATIONS

1.Liver cysts can also rupture

• through the diaphragm producing an empyema,

• into the biliary tract producing obstructive jaundice, or

• into the stomach.

2.Cyst rupture or leakage can cause immunologic symptoms from the

initiation of an immunoglobulin (Ig)E response, leading to allergic reactions

most frequently characterized by hives, flushing, and mucous membrane

swelling.

3.A major rupture can cause a life-threatening anaphylactic reaction.

4.Ruptured cysts can release viable cystic contents and protoscolices into

the peritoneum, resulting in secondary hydatidosis (implanting and growing

within the peritoneal cavity).

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DIAGNOSIS

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CLINICAL

1. Signs and symptoms may include

hepatic enlargement with or without a palpable mass in the

right upper quadrant,

right epigastric pain,

nausea, and

vomiting.

2. On per abdominal examination,

3. When the cyst involves the lower margin of the liver

i. A palpable spherical and smooth swelling may be felt in

the right hypochondrium

ii. Hydatid thrill positive (rarely demonstrated)

4. When the cyst involves the superior margin,

5. Upper limit of liver dullness is found to be raisedAkriti Sah

RADIOLOGICAL

1. ON ULTRASOUND

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RADIOLOGICAL

1. ON ULTRASOUND

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1. Shows a well-defined cystic lesion.

2. The cyst wall usually has a hypoechoic layer, flanked by an

echogenic line on either side.

3. At times the endocyst can also detach from the pericyst. This

detachment may appear as a localized split in the wall and “floating

membranes” within the cystic cavity;

4. Complete detachment the endocyst observed by ultrasonography is

referred to as the water lily sign.

5. Multivesicular cysts may also be seen which are fluid collections

that often appear in a honeycomb pattern with multiple septa. These

septa represent the walls of the daughter cysts, which appear as

cysts within a cyst.

6. Multiple punctate echogenic foci are often present within the cyst,

appearing grain-like. These foci represent hydatid sand, a

combination of fluid and protoscolices. Akriti Sah

The findings on imaging vary

depending on the stage of the cyst.

A classification system originally developed

by Gharbi and colleagues in 1981, was revised

by the WHO-Informal Working Group

Classification on Echinococcus (IWGE).

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Ultrasound has become a widely used modality for

CE detection.

This is currently the screening method of choice,

due in part to

• accessibility even in small, rural medical centers,

• cost containments, and

• portability of the device.

Ultrasound is not only helpful for diagnosis, but in

post-treatment monitoring.

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2. ON CT

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1.CT plays a crucial role during the peri-

operative period for detection of complications,

such as

•biliary and vascular involvement,

•cyst ruptures, and

•underlying infection.

2.In addition, CT can reveal many of the same

findings that can be seen by ultrasonography.

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SEROLOGY1.Infection with Echinococcus induces an antibody

response, most commonly IgG (predominantly IgG1 and

IgG4), followed by IgM, IgA, and IgE.

2.A number of detection assays for IgG, IgM, and IgE

antibodies to hydatid antigens are in use.

3.Serologic tests, such as enzyme-linked immunosorbent

assay (ELISA) and indirect hemagglutination test, are

highly sensitive methods for detecting infection.

4.Specific confirmation can be obtained by demonstrating

echinococcal antigens by immunodiffusion (arc 5)

procedures or immunoblot assays (8-, 21 –kD bands).

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1.Although antibody detection assays tend to have higher

sensitivities (up to 97%) when compared to antigen assays,

they do not distinguish between active and past infections.

Therefore, assays for antigens are preferred, as they are not

only more specific, but levels have been shown to reflect

improvement in surgically treated patients

2.A disadvantage of these assays is the variability in sensitivity

rates, which range from 33% to 85%. This variability may be

due to the structure of calcified cysts, concealment of cysts

by surrounding normal tissue, or the fact that antigen–

antibody complexes are not easily detected by assays.

3.However, in approximately 30–40% of patients, no

antibodies of any kind are detectable, even in individuals who

have circulating parasitic antigens. These data suggest that

the infection may be associated with an inhibition of the host

immune response. Akriti Sah

In conclusion,

1.Ultrasonography imaging is the technique of

choice for the diagnosis .This technique is

usually complemented or validated by

computed tomography (CT) and/or magnetic

resonance imaging (MRI) scans.

2.After a cyst has been detected, serologic

tests may be used to confirm the diagnosis.

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REFERENCES

1.Bailey & Love's Short Practice of Surgery,

26E

2.Park’s preventive and social medicine,26E

3.Medical Parasitology by Arora, 4E

4.www.who.int/

5.www.cdc.gov/

6.www.ncbi.nlm.nih.gov/

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WHAT’S NEW?

Vaccination of lambs is currently being evaluated as an additional intervention.

WHO is working towards the validation of effective cystic echinococcosis control

strategies by 2020.

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