Alveolar echinococcosis: causes, symptoms, diagnosis, treatment

Alveolar echinococcosis (alveolar echinococcosis, multilocular echinococcosis, Latin alveococcosis, English alveococcus disease) is a zoonotic chronic helminthiasis, which is characterized by the development of cystic formations in the liver, capable of infiltrative growth and metastasis to other organs.

ICD-10 codes

• D67.5. Liver invasion caused by Echinococcus multilocularis.
• 867.6. Invasion of other localizations and multiple echinococcosis caused by Echinococcus multilocularis.
• 867.7. Infestation caused by Echinococcus multilocularis, unspecified.

Epidemiology of alveolar echinococcosis

The source of alveolar echinococcosis for humans is the final hosts of the helminth. Mature eggs and segments filled with eggs are released into the environment with animal feces. Humans become infected when oncospheres from the environment enter their mouths during hunting, processing the skins of killed wild animals, or eating wild berries and grasses contaminated with helminth eggs. Alveococcus oncospheres are very resistant to environmental factors: they can withstand temperatures from -30 to +60 °C, and remain viable for a month on the soil surface at a temperature of 10-26 °C.

Alveococcosis is a natural focal disease. The factors that determine the activity of foci are the abundance of intermediate hosts (rodents), large areas (meadows, pastures) that are not plowed, cool rainyclimate. Diseases are mainly observed among people visiting natural foci for professional or everyday reasons (picking berries, mushrooms, hunting, hiking, etc.), as well as among workers of fur farms. Family cases of infection are also noted. There is no pronounced seasonality. Men aged 20-40 years are more often ill, children rarely get sick.

In Russia, the disease is found in the Volga region, Western Siberia, Kamchatka, Chukotka, the Republic of Sakha (Yakutia), Krasnoyarsk and Khabarovsk Krai, in the CIS countries - in the republics of Central Asia, Transcaucasia. Endemic foci of alveococcosis are found in Central Europe, Turkey, Iran, in the central regions of China, northern Japan, Alaska, and Northern Canada.

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What causes alveolar echinococcosis?

Alveolar echinococcosis is caused by Alveococcus multilocularis, which develops with a change of hosts. The final hosts of alveococcus are carnivores (foxes, arctic foxes, dogs, cats, etc.), in whose small intestine the mature forms parasitize. The intermediate hosts are rodents. The mature form of A. multilocularis is similar in structure to the tape stage of E. granulosus, but is smaller in size (length 1.6-4 mm), the head is equipped with one crown of short hooks, the uterus is spherical. But the main difference is in the structure of the cyst, which in A. multilocularis looks like a cluster of bubbles and is a conglomerate of exogenously budding small bubbles filled with liquid or gelatinous mass. In humans, the bubbles often do not have scolexes. The growth of the cyst is slow, over several years.

Pathogenesis of alveolar echinococcosis

In humans, the larva of A. multilocularis develops for 5-10 years or more. The development and growth rate of the parasite may be due to the genetic characteristics of the indigenous population in endemic foci. The larval form of alveococcus is a dense, finely tuberous tumor, which consists of a conglomerate of small vesicles. In section, it resembles fine-pored cheese. The alveococcal node is a focus of productive necrotic inflammation. A granulation ridge containing live alveococcal vesicles is formed around the foci of necrosis. The features of alveococcus are infiltrating growth and the ability to metastasize, which brings this disease closer to malignant tumors. The liver is always primarily affected. Most often (75% of cases), the parasitic focus is localized in its right lobe, less often - in both lobes. Solitary and multinodular liver damage is possible. Parasitic nodes are round, ivory-colored, from 0.5 to 30 cm or more in diameter, with a gland-like density. The parasitic node can grow into the bile ducts, diaphragm, and kidney. Compensation of the organ function is possible due to hypertrophy of the unaffected parts of the liver. In the complicated stage of alveolar echinococcosis, necrotic cavities (caverns) of various shapes and sizes almost always appear in the center of the alveolar nodes. The wall of the cavern can become thinner in places, which creates the prerequisites for its rupture. Actively multiplying parasite vesicles in the peripheral zone of the node are introduced into the liver tissue along the vascular-duct structures, into the gallbladder. Obstructive jaundice develops, and in the later stages - biliary cirrhosis. The alveococcal node can grow into adjacent organs and tissues (lesser and greater omentum, retroperitoneal tissue, diaphragm, right lung, right adrenal gland and kidney, posterior mediastinum). Metastasis to the lymph nodes of the retroperitoneal tissue, lungs, brain, and bones is possible.

In the pathogenesis of alveolar echinococcosis, an important role is played by immunological and immunopathological mechanisms (immunosuppression, formation of autoantibodies). It has been established that the growth rate of the larva depends on the state of cellular immunity.

Symptoms of alveolar echinococcosis

Alveococcosis is detected mainly in young and middle-aged people. Often the disease is asymptomatic for many years (preclinical stage). The stages of the disease are: early, uncomplicated. complications and terminal stage. In the clinically manifest stage, the symptoms of alveolar echinococcosis are not very specific and depend on the volume of parasitic lesion, its localization and the presence of complications. According to the nature of the course, a distinction is made between slowly progressing, actively progressing and malignant alveolar echinococcosis.

The first symptoms of alveolar echinococcosis are liver enlargement, which is usually discovered by accident. Patients report a feeling of pressure in the right hypochondrium or in the epigastric region. A feeling of heaviness and dull, aching pain appear. An enlarged and asymmetrical abdomen is often noted. A dense liver with an uneven surface is palpated through the anterior abdominal wall. The liver continues to enlarge, becoming woody-dense, lumpy and painful to palpation. Patients note such symptoms of alveolar echinococcosis as weakness, loss of appetite, weight loss; as a rule, ESR is significantly increased. Inconstant eosinophilia, lymphopenia are detected, anemia is possible. Hyperproteinemia with hypergammaglobulinemia appears early. Biochemical test results remain within normal limits for a long time. At this stage, obstructive jaundice most often develops, which is especially characteristic of the central localization of the parasitic tumor. It begins without pain and increases slowly, accompanied by skin itching, increased concentration of conjugated bilirubin, alkaline phosphatase activity. In cases where a bacterial infection joins in, a clinical picture of a liver abscess develops. A breakthrough of the contents of a parasitic cyst into the bile ducts occurs rarely. When the cavity is opened, bronchohepatic, pleurohepatic fistulas may form, peritonitis, pleurisy, and pericarditis may develop. Portal or caval hypertension occurs less often than jaundice. Symptoms of portal hypertension (varicose veins on the anterior abdominal wall, varicose veins of the esophagus and stomach, hemorrhoidal veins, splenomegaly, hemorrhagic manifestations, ascites) occur in the late stages of alveococcosis. The most dangerous complication of portal hypertension is bleeding from the veins of the esophagus and stomach. Metastases are most often found in the lungs, brain, less often in the kidneys and bones. More than 50% of patients have renal syndrome: proteinuria, hematuria, pyuria, cylindruria. Kidney damage can be caused by compression of the organ from the outside or due to metastases, impaired renal blood flow and urine passage with the development of urinary tract infection. Due to the addition of immunopathological processes, chronic glomerulonephritis, systemic amyloidosis with chronic renal failure are formed. Alveococcosis is more severe and rapid in visitors to endemic foci, in people with immunodeficiency, during pregnancy and its termination, with severe concomitant diseases.

Diagnosis of alveolar echinococcosis

Diagnosis of alveolar echinococcosis is based on data from the epidemiological history, clinical, laboratory and instrumental studies.

Serological diagnostics of alveolar echinococcosis is used: RLA, RIGA, ELISA; PCR can be used, however, a negative reaction does not exclude the presence of alveolar echinococcosis in the subject.

X-ray examinations, ultrasound, CT and MRI allow to assess the degree of organ damage. In general radiographs of the liver of a patient with alveococcosis, one can see small foci of calcification in the form of so-called calcareous splashes or calcareous lace. Laparoscopy is also used for targeted biopsy of the alveococcal node, but it can be performed only after excluding hydatid echinococcosis. In obstructive jaundice caused by alveococcosis, both visual (EGDS, laparoscopy) and direct radiocontrast methods (retrograde pancreatocholangiography, antegrade, percutaneous, transhepatic cholangiography) are used. The advantage of these research methods, in addition to high information content, is the possibility of using them as therapeutic measures, mainly for decompression of the biliary tract.

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Differential diagnosis of alveolar echinococcosis

Alveococcosis of the liver must be differentiated from hydatinous echinococcosis, neoplasms of the choledochopancreatic region, amoebic abscess, and liver cirrhosis.

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Treatment of alveolar echinococcosis

Indications for consultation with other specialists

Surgical treatment of alveolar echinococcosis is performed after approval by the surgeon.

The regimen and diet are indicated for complicated cases of alveolar echinococcosis.

Chemotherapeutic treatment of alveolar echinococcosis is used as an additional remedy. Albendazole is used in the same doses and regimen as for hydatid echinococcosis. The duration of the course of treatment depends on the patient's condition and drug tolerance. In cases of severe jaundice, liver and kidney dysfunction, suppuration of the decay cavity, and in the terminal stage of the disease, antiparasitic treatment is not recommended.

If possible, total surgical removal of the alveolar echinococcosis node of the liver within the intact tissues is performed. In case of bleeding from the veins of the esophagus, the most effective method of conservative treatment is compression of the veins of the esophagus with a Blackmore probe. Palliative operations in combination with chemotherapy can improve the patient's condition for a long time. In recent years, more than 50 liver transplants have been performed in patients with alveolar echinococcosis in different countries of the world, however, despite careful preoperative examination, there are many cases of relapse of the process or metastasis.

Forecast

Serious if surgical treatment of alveolar echinococcosis is impossible.

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Clinical examination

Outpatient observation of a patient who has recovered from the disease after surgery lasts 8-10 years with examination at least once every 2 years. Only persons who have shown a negative result in three or four serological tests over 3-4 years are removed from the register. If clinical signs of relapse or an increase in antibody titers in serological reactions appear, examination in a hospital setting is indicated. Patients with inoperable forms of the disease remain disabled and are monitored for life.

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How to prevent alveolar echinococcosis?

Alveolar echinococcosis is prevented by the same methods as for hydatid echinococcosis.