Echinococcosis

Echinococcosis is a disease associated with the penetration into the human body and development of the larval stage of the tapeworm Echinococcus granulosus.

ICD-10 code

B-67. Echinococcosis

What is echinococcosis?

The sexually mature echinococcus worm parasitizes the intestines of the final host - a dog. The number of worms in the body of the final host can reach several thousand. The worm consists of a head with four suckers and hooks, two or three segments, the last of which contains a uterus filled with parasite eggs. The number of eggs reaches 400. Each egg has a dense chitinous shell and contains a larva. Echinococcus releases eggs into the environment, where they are eaten by intermediate hosts (sheep, cows, pigs and camels). In their body, an intermediate stage of the parasite develops - cystic. After the death or slaughter of the intermediate hosts, the diseased organs of the animals are eaten by dogs, in whose body sexually mature worms then develop. Thus, the cycle of echinococcus development is closed.

A person becomes infected with echinococcus by accidentally eating the parasite's eggs. After the echinococcus eggs enter the human body, their shell dissolves under the influence of gastric juice, and the released larva penetrates the stomach or intestinal wall into the bloodstream and is carried into the liver capillaries. In 80% of infected patients, it gets stuck there and begins to develop. If the larva bypasses the liver capillaries, it is carried by the bloodstream into the lung capillaries, where it can also linger and cause lung damage. A similar situation is observed in about 15% of cases. If the larva bypasses the lung capillaries or penetrates the systemic circulation through the open oval window, it can be carried into any organ or tissue of the body (spleen, kidneys, brain, subcutaneous tissue, etc.).

In the liver, the parasite larva actively grows, turning into a bubble up to 1 mm in diameter after a month, and after five months the bubble can reach 55 mm. The echinococcal bladder constantly grows due to the host's nutrients and can eventually reach a volume of 10-20 and even 30 liters. The echinococcal cyst has a characteristic structure and exhibits appositional growth, pushing aside the surrounding tissues, but not growing through them. It is filled with a transparent liquid containing succinic acid. From the inside, the formation is lined with a single-layer cubic epithelium (germ layer). Outside of it, there is a dense chitinous shell - a product of the parasite's vital activity. It is white and similar in appearance to the protein of a boiled egg. From the outside, the cystic formation is surrounded by a dense connective tissue fibrous capsule, which consists of the tissues of the host's body and fences it off from the parasite. If the cyst exists for a long time, the fibrous membrane can reach a thickness of up to 1 cm or more. Inside the echinococcal cyst, daughter vesicles bud off from the germ layer, from which, in turn, granddaughter vesicles bud off, etc. In addition, it contains many parasite embryos (echinococcal sand), which float in the liquid.

Epidemiology

Echinococcosis is widespread mainly in countries with developed livestock farming. People who are involved in servicing domestic animals by their occupation fall ill - shepherds, milkmaids, as well as people who have contact with dogs, especially children who play with them and allow their pets to lick their faces and sniff food products.

Echinococcosis is most common in Latin American countries, where up to 7.5 cases per 100,000 people are registered per year. It is also found in Central Asia, Australia, New Zealand and Europe. Of the European countries, the disease is common in Italy, Bulgaria and Iceland. In Russia, it is registered mainly in the Caucasus, along the middle and lower reaches of the Volga, in Western Siberia, Yakutia (Sakha) and Chukotka. Mostly young people of working age fall ill, but the disease is also found in small children and the elderly. Recently, the disease has been registered outside endemic foci, which is associated with increased population migration.

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How does echinococcosis manifest itself?

Echinococcosis and its manifestations depend on the location and size of the cysts.

In the first period of the disease (in the asymptomatic stage), patients may be bothered by allergic reactions of the body to the introduced parasite: skin itching, urticaria, the appearance of papules on the skin. These symptoms are characteristic of any helminthic invasion and are especially pronounced in children. During a physical examination of the patient at this stage, it is usually impossible to detect any abnormalities. Only special laboratory and instrumental examination can help in diagnosis.

In the uncomplicated stage of the disease, patients with echinococcosis complain of dull constant pain and a feeling of heaviness in the right hypochondrium, dyspeptic symptoms and a feeling of fullness in the stomach after meals. During an objective examination, some patients are found to have a formation in the liver that is round in shape, of a dense elastic consistency and slightly painful upon palpation.

At the stage of pronounced clinical manifestations and complications, the clinical picture of the disease is quite pronounced. Patients with echinococcosis are bothered by constant dull pain and a feeling of heaviness in the right hypochondrium. When palpating the liver, a "tumor" of a rounded shape, dense elastic consistency, sometimes reaching large sizes, can be determined. Rarely, "hydatid tremor noise" can be observed above the tumor. In children, with large cysts, chest deformation is often observed - "echinococcal hump". Further manifestations depend on the nature of the complications that have developed.

Echinococcosis of the liver may undergo aseptic necrosis with subsequent calcification. In this case, a stony-density node is formed in the liver, which can be detected by palpation and special examination methods. The general condition of patients suffers little, and the clinical picture is limited to the presence of pain, a feeling of heaviness in the right hypochondrium and appetite disorders with progressive weight loss. In case of suppuration of the cyst, the symptoms correspond to the manifestations of a liver abscess: severe condition of the patient, hectic temperature with signs of an inflammatory reaction in the blood test, severe constant pain in the right hypochondrium.

A growing cystic formation can compress the bile ducts. In such a situation, the patient is diagnosed with mechanical jaundice with yellowish coloration of the skin and sclera, skin itching, discoloration of feces and darkening of urine. Patients become lethargic and adynamic. When the veins in the liver gates are compressed, symptoms of portal hypertension with the appearance of ascites, splenomegaly, esophageal and hemorrhoidal bleeding are present.

Due to minor trauma, a large cystic formation can break through into the free abdominal or pleural cavity and even into the pericardial cavity, as well as into the bile ducts. A cyst breakthrough is characterized by the development of severe allergic shock, which can be fatal. If a patient with echinococcosis survives, he develops echinococcal peritonitis, pleurisy or pericarditis. In this case, the daughter bubbles and scolexes of the parasite that have spilled into the cavity are fixed on the peritoneum and pleura, where they begin to progress and develop. The number of such cysts in the abdominal cavity can reach several dozen. When a cyst breaks into the bile ducts after anaphylactic shock, violent cholangitis and mechanical obstruction of the bile ducts with the development of mechanical jaundice develop.

In approximately 5-7% of cases, when the cyst is located on the diaphragmatic surface of the liver, the lung fuses with the diaphragm and when the cyst breaks, a connection is formed between its cavity and the bronchial tree. A bile-bronchial fistula is formed. The clinical picture of this complication is quite typical. Complaints of cough with the release of a large amount of transparent sputum and films - scraps of the chitinous shell of the cyst. Later, the sputum becomes bilious. Its amount increases after meals and when the patient is lying down, which forces patients to sleep sitting up.

Echinococcosis of the lung manifests itself as chest pain and shortness of breath. If the bladder suppurates, a lung abscess is possible; if the bladder breaks into the bronchi, a painful cough and hemoptysis suddenly appear, the contents of the echinococcal bladder - fragments of membranes and scolexes - are released from the bronchi.

In echinococcosis of other localizations, symptoms of extensive organ damage dominate.

Due to the late diagnosis of echinococcosis, the incidence of complications in patients is high and usually amounts to 10-15%.

Classification

There are three clinical stages of echinococcosis:

• asymptomatic stage;
• uncomplicated stage;
• stage of complications.

According to diameter, cysts are divided into the following:

• small (up to 5 cm);
• medium (5-10 cm);
• large (11-20 cm);
• giant (21 cm and more).

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Screening

Screening studies are possible and advisable in foci of echinococcosis among the most susceptible population groups (livestock breeders, shepherds, agricultural workers). They conduct an examination, perform immunological reactions and ultrasound.

How to recognize echinococcosis?

Laboratory and instrumental studies

In the presence of a live echinococcal cyst, changes characteristic of helminthic invasion (eosinophilia and increased ESR) are observed in the blood. With the development of liver failure, the activity of transaminases (aspartate aminotransferase and alanine aminotransferase) increases. With mechanical jaundice, the concentration of direct serum bilirubin and urine urobilin increases.

Immunological reactions hold a special place in the diagnostics of echinococcosis. In 1911, Tomaso Casoni proposed a reaction that later received his name. He injected 0.1 ml of echinococcal fluid into the patient intradermally, and an isotonic sodium chloride solution into the opposite forearm. Redness appeared on the side where the fluid was injected, and a papule formed. Since then, this reaction has been widely used to diagnose echinococcosis.

The Casoni reaction is positive in approximately 90% of patients, but its specificity is too low. In this regard, a number of other immunological reactions (hemagglutination, complement fixation, etc.) have been proposed to improve diagnostics. The possibility of developing anaphylactic shock, especially when conducting repeated immunological reactions, significantly limits their use in everyday clinical practice. With the introduction of new diagnostic instrumental methods into practice, these reactions have lost their original significance.

Currently, ultrasound is considered the "gold standard" in echinococcosis diagnostics. Due to its non-invasiveness, availability and effectiveness, it is very convenient and is usually sufficient to establish an accurate diagnosis. It can detect the presence of cysts in the liver, their size, location, the presence of daughter vesicles and determine the nature of the blood flow in the cyst area using Doppler imaging.

In case of calcification of the cyst, plain radiography reveals a round shadow, sometimes with a rim, in the liver. CT has a high diagnostic value, which helps to solve many tactical treatment issues.

With the introduction of ultrasound and CT into widespread clinical practice, such invasive methods of diagnosing echinococcosis as celiacography, portohepatography, laparoscopy and radioisotope examination of the liver have lost their significance.

Differential diagnostics

Echinococcosis usually requires differential diagnosis with other focal organ lesions - cysts, benign and malignant neoplasms and alveococcosis. In case of suppuration, the cyst should be differentiated from a bacterial abscess, and in case of mechanical jaundice - from other causes. The decisive importance in differential diagnosis should be given to the anamnesis and modern instrumental research methods.

Epidemiological history (place of residence, type of work, contact with dogs), the presence of eosinophilia and identification of focal lesions of the liver, lungs or other organs allow for a more precise diagnosis.

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Example of diagnosis formulation

Echinococcosis of the liver (uncomplicated or complicated) with indication of complications (calcification, suppuration, breakthroughs in body cavities, bronchial tree, portal hypertension, mechanical jaundice).

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How is echinococcosis treated?

Treatment goals

The goal of treatment is to remove parasitic cysts from the liver, lungs and other organs and create conditions that help prevent relapse of the disease. All patients with echinococcosis require treatment in a surgical hospital.

Surgical treatment

Indications

The presence of echinococcosis of internal organs is an absolute indication for surgical intervention.

Contraindications

Only the presence of severe concomitant diseases and intolerance to surgery makes one refrain from surgery. The volume and nature depend on the size of the echinococcal cyst, its topography and the presence of complications.

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Surgical treatment methods

For liver surgery, a two-subcostal approach is most often used, allowing for examination of all parts of the liver and intervention. Many surgeons limit themselves to a midline laparotomy or an oblique incision in the right hypochondrium.

The most radical operation is liver resection within healthy tissues. Indications for its implementation are:

• multiple echinococcosis with cysts localized within a lobe or half of the liver;
• marginal location of the cyst;
• recurrent echinococcosis.

Pericystectomy is an operation to excise a cyst together with a fibrous capsule with minimal damage to liver tissue. The operation is quite radical and may be accompanied by significant blood loss, so modern hemostasis methods must be used.

The most common and fairly safe operation for the patient is considered to be echinococcectomy. In this type of surgical intervention, the cyst is initially punctured and an antiparasitic agent, such as iodine tincture, is injected into its lumen. Then the cyst is opened and the contents (daughter blisters, fluid, and echinococcal sand) are removed along with the chitinous membrane. Next, the walls of the fibrous capsule are treated with glycerin, formalin, or iodine tincture, and the remaining cavity is closed by suturing (capitonage), gluing, or tamponade with an omentum on a leg. In recent years, there have been reports that fairly frequent relapses after such an intervention are associated with the penetration of the parasite's scolexes into the cracks of the fibrous capsule. To improve the results of echinococcectomy, it has been proposed to partially excise the walls of the fibrous capsule and treat the remaining tissues with glycerin, a laser beam, or a cryodestructor (Fig. 34-8). Nowadays, in a certain proportion of patients, echinococcectomy is performed using laparoscopic techniques.

Percutaneous puncture of the cyst with removal of its contents and introduction of sclerosing agents is permissible in exceptional cases when the cystic formation is solitary, marginal and without daughter vesicles. This intervention is fraught with the development of anaphylactic shock and generalization of the process when echinococcal fluid enters the abdominal cavity.

Possible postoperative complications

The most serious complications after surgeries for echinococcosis are liver failure, blood and bile leakage into the abdominal cavity. Reactive basal pleurisy often occurs after surgeries for subdiaphragmatic cysts.

Conservative treatment

In recent years, albendazole and its derivatives have been used to treat echinococcosis. The drug is prescribed in courses of 10-20 mg per kilogram of body weight per day. The course of treatment lasts 30 days. After 15 days, the course is repeated. To cure the patient, 3-5 such courses are necessary. Drug treatment is often used as an addition to surgical treatment to prevent relapses of the disease and in patients who cannot undergo surgery due to the severity of concomitant diseases. The effectiveness of albendazole treatment of hydrative echinococcosis of the liver and lungs is 40-70%.

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Further management

After radical interventions for a disease such as echinococcosis, patients need inpatient treatment for two weeks. In cases where the residual cavity heals for a long time by secondary intention, inpatient treatment is increased to a month or more. If the postoperative period is favorable, the patient can return to work not related to physical activity a month after the operation. The latter is allowed 3-6 months after the patient's recovery.

All patients after interventions for echinococcosis are recommended to undergo a course of treatment with albendazole and subsequent dispensary observation due to a fairly high risk of relapse (10-30%). Control ultrasound should be performed 3-6 months after surgery to promptly detect a possible relapse of the disease. After radical interventions for echinococcosis and courses of drug treatment, patients are usually practically healthy and able to work. If relapses of the disease are detected, repeated intervention is necessary.

How to prevent echinococcosis?

The main role in infection with the parasite is played by non-observance of hygiene rules. Disease prevention measures are well developed and include state and personal prevention. State prevention consists of decreeing a ban on backyard slaughter of livestock. Livestock should be slaughtered only in meat-packing plants or special veterinary areas with culling and destruction of organs affected by echinococcus. Impact on echinococcosis of definitive hosts in endemic foci includes the destruction of stray dogs and deworming of service and domestic dogs twice a year. Personal prevention - strict observance of personal hygiene rules, especially after contact with animals.