What is Liver Echinococcosis?
Echinococcosis of the liver (echinococcosis hepatis) is a human helminthiasis caused by the introduction and development of tapeworm larvae Echinococcus granulosus and E. (Alveococcus) multilocularis in the liver.
Echinococcosis of the liver occurs in two varieties – cystic and alveolar (multi-chamber). In Russia and neighboring countries, echinococcosis is mainly distributed in Central Asia, Kazakhstan, Georgia, Crimea, Siberia (Novosibirsk, Omsk, Tomsk regions), and Yakutia.
Bubble (single-chamber, racemose, hydatidosis) echinococcosis in about half of cases occurs with liver damage, moreover, the cyst is more often localized in the right lobe, occasionally several cysts are observed. The pathogenic effect of echinococcus on the body is determined by the mechanical pressure of the echinococcal cyst on the liver and neighboring organs, as well as the toxic and sensitizing effect of the parasite.
Causes of Echinococcosis of the Liver
The causative agent of human echinococcosis is the larval stage of the echinococcus tapeworm – Echinococcus granulosus.
The sexually mature form of echinococcus is a small cestode 2.5 – 5.4 mm long and 0.25 – 0.8 mm wide. It consists of a pear-shaped scolex, neck and 3-4 segments.
Skoleks is equipped with four suction cups and a crown from two rows of hooks (28 – 50).
Behind the scolex there is a short neck and joints, the first two are immature, the third hermaphroditic and the fourth mature. The mature segment (length 1.27 – 3.17 mm) is filled with a stretched uterus, which is a wide longitudinal trunk with lateral protrusions. The uterus is packed with eggs (400 – 600 pieces), which do not differ in structure from the eggs of bovine and pork tapeworms (teniids), which contain a six-hooked oncosphere inside.
The sexually mature form – echinococcus tapeworm – parasitizes only in animals: dogs, wolves, jackals, foxes, which are the ultimate hosts. The larval stage – an echinococcal cyst – parasitizes in intermediate hosts – various herbivorous and omnivorous ungulates (sheep, goats, cattle, pigs, horses, etc.) and humans.
Echinococcal cyst is a bubble of a very complex structure. Outside, it is surrounded by a layered membrane (cuticle), the thickness of which sometimes reaches 5 mm. Under the multilayer cuticular membrane lies a thin inner germinal (germinative) membrane, which produces brood capsules with scolexes, daughter blisters, and also gives rise to the layered membrane.
Brood capsules are small vesicle-shaped formations scattered on the germinal membrane and connected to it by a thin leg. They have the same structure as the main bladder, but with the opposite arrangement of the shells (germinate on the outside, layered on the inside). Each brood capsule contains scolexes attached to its wall, screwed inward and having a typical structure for chains. The bubble is filled with a liquid that acts as a protective nutrient medium for brood capsules and scolexes.
The liquid may contain freely weighed, detached scolexes and brood capsules, the so-called hydatidose sand.
The bladder is gradually covered with a connective tissue membrane. Often in such a maternal cyst, in addition to the above listed elements, there are also so-called daughter bubbles, which have the same structure, and granddaughter bubbles inside them.
Such cysts are observed in humans. Sometimes daughter bubbles do not form inside the maternal cyst, but on the outside. Such bubbles are called exogenous.
Echinococcal cysts formed in animals, as a rule, do not contain brood capsules and scolexes, they are called acephalocysts. In humans, this form does not occur.
In the sheep-breeding areas of the southern zone, the echinococcus circulation follows the pattern: sheep – ›guard dogs accompanying the flock -› sheep.
In the western regions of intensive pig breeding, the echinococcus circulation follows the pattern: pigs – ›dogs -› pigs. The lack of active motor function in the members of the “swine” strain reduces the contamination of dog hair and soil, thereby limiting the conditions of infection of people and animals.
The intensity of invasion transmission is determined, first of all, by the number of sources of invasion of the final hosts and the amount of invasive material released by them – oncospheres and segments.
The oncospheres tolerate temperatures from -30 ° C to + 38 ° C, they remain viable for a month on the surface of the soil in the shade at a temperature of 10 – 26 ° C, but die in the sun at a temperature of 18 – 50 ° C after 1-5 days. In the grass at a temperature of 14 – 28 ° C, they die no earlier than after 1.5 months. Oncospheres tolerate low temperatures, at which they can persist for several years, but are very unstable to dry.
The invasion in echinococcosis is circulated according to the well-known pattern: the source of invasion (the final hosts are carnivores) – ›the external environment polluted by the oncospheres and segments of the parasite, -› the intermediate host (herbivores, omnivores, infected with larvae) – ›the uninfected final host.
Man – an intermediate host – is a biological dead end.
With human echinococcosis, the dog occupies the main position as the final host. Dogs become infected when they eat meat from slaughterhouses, slaughter areas, kitchens, when they feed them confiscated slaughterhouses or organs of animals slaughtered at home affected by larvocists. It is also possible that dogs are infected by feeding them hunting products – affected organs or corpses of wild herbivores.
Ways of infection of intermediate hosts are also different, herbivorous farm animals become infected by swallowing eggs, segments of helminth with grass, hay, water, contaminated with feces of invaded dogs. Pigs, being coprophagous, become infected by eating dog feces. The main role in infecting a person through dirty hands is played by communicating with invasive dogs, the hair and tongue of which can contain eggs and segments of echinococcus chains. Healthy animals can also transmit invasion to humans as mechanical carriers of eggs that contaminate their hair, tongue when licking an infected dog.
Human infection is not excluded when eating unwashed vegetables, berries, fruits contaminated with feces of dogs containing oncospheres.
A person can also become infected from wild carnivores during hunting when cutting hides, making fur clothes, as well as eating unwashed wild berries and drinking water from natural reservoirs.
In sheep-breeding areas, where the pathogen is mainly circulated between dogs and sheep, risk groups include shepherds, shepherds accompanying flocks, and sheared sheep’s wool and family members.
Pathogenesis during Echinococcosis of the Liver
Echinococcosis develops in connection with the introduction and growth in various organs of the tape worm larva – echinococcus.
A person is infected with echinococcosis mainly orally, and due to the hematogenous pathway of the oncosphere, it can affect any organ, any tissue, but most often the liver (44 – 85%), then the lungs (15 – 20%) in more rare cases, in a large circle of blood circulation – kidneys, bones, brain and spinal cord and other organs.
The pathological effect of echinococcus is due to the mechanical and sensitizing effect of the growing larva. The sizes of cysts are from 1 – 5 cm in diameter to giant cysts containing several liters of fluid. The mechanical effect of such a cyst leads to impaired function of the affected organ. Localization and size determine the main symptomatology and severity of the disease.
Sensitization of the body by parasite metabolism leads to the development of immediate and delayed hypersensitivity. A striking manifestation of an allergic reaction of an immediate type is eosinophilia and urticaria as a result of leakage of echinococcal fluid, and in more severe cases (when opening the bladder) anaphylactic shock. In the late stages of the disease, especially with multiple echinococcosis, an important role is played by immunopathological reactions.
At the beginning of the development of the parasite in the human body, it is a bubble filled with a colorless liquid with a diameter of about 1 mm, which increases in size over time. The hydatid wall consists of the inner (germinative) and externally (chitinous or cuticular) membranes. Outside, such an echinococcal cyst has a dense fibrous membrane consisting of connective tissue and resulting from the reaction of liver tissue in response to the presence of a parasite. This membrane is very dense and practically inseparable from a healthy liver parenchyma, but can be separated from the chitinous membrane. The only functionally active is the vyuterny germinal shell of the hydatide, which constantly forms new germinal scolexes. As they ripen in the fluid of the echinococcal cyst, so-called daughter (and later grandchild) bubbles form in them. In addition, the germinal membrane in the lumen of the cyst secretes hydatid fluid and is involved in the formation of the outer chitinous membrane of the parasite. In more than 80% of patients, the right lobe of the liver is affected; in 1/2 patients, multiple cysts are detected.
Symptoms of Echinococcosis of the Liver
There are two forms of echinococcosis: cystic (hydatidous) and alveolar. The hydatidose form of echinococcosis defines a disease caused by a cystic or larval stage of development of echinococcosis tape worm Echinococcus granulosus.
For a long time (sometimes for many years), starting from the moment of infection, there are no clinical signs of the disease, and the person feels almost healthy. Clinical manifestation of the disease begins only when hydatides of rather large sizes are reached. There are dull, aching, constant pains in the right hypochondrium and epigastric region, in the lower parts of the right half of the chest. On examination, in case of large sizes of the cyst, a bulging of the anterior abdominal wall in the right hypochondrium can be detected. Percussion marked expansion of the borders of the liver up. With palpation of the liver, a rounded, elastic consistency tumor formation can be determined (with the localization of large echinococcal cysts in the antero-lower parts of the liver). With localization of cysts, hepatomegaly is observed deep in the liver parenchyma.
By localization, three types of echinococcus of the liver are distinguished: anterior, descending (abdominal) and ascending (thoracic). With a large volume of the anterior cysts, the region of the liver expands greatly. Upper cysts simulating an effusion pleurisy are determined by fluoroscopy by the high position of the diaphragm on the right with a domed protrusion of the location of the cyst. With lower cysts, the tumor can be felt in the abdominal cavity, it moves with breathing with the liver, and has an elastic consistency. Cysts localized in the left lobe of the liver become accessible by palpation in later periods of the disease.
The worsening of the condition is associated with an allergic reaction of the body to the presence of a live parasite, which manifests itself in the form of urticaria, diarrhea, etc. The symptomatology of the disease changes when large organs are compressed by adjacent cysts. The most common complications of the hydatidose form of echinococcosis: jaundice, rupture of a hydatidosis cyst, suppuration of a hydatidosis cyst. Jaundice (mechanical) is associated either with compression by the cyst of the main biliary tract, a breakthrough of the cyst in the bile duct (in 5-10% of patients). Ascites rarely occurs (5-7%) with compression of the portal vein.
Hydatidosis cyst rupture can occur with the outflow of contents into a kind of abdominal cavity, into the lumen of the gastrointestinal tract, into the bile ducts, into the pleural cavity or in the bronchus. The most serious complication is perforation of the cyst into the free abdominal cavity. Symptoms of anaphylactic shock and widespread peritonitis occur. Perforation of the cyst in the free abdominal cavity significantly worsens the prognosis of the disease in connection with the dissemination of the process.
Suppuration of an echinococcal cyst is associated with the formation of a crack in the hydatid capsule, especially if there is a message with bile ducts. The bacteria in the bile are a source of infection. With suppuration of an echinococcal cyst, severe pain in the liver, hepatomegaly, hyperthermia, and other symptoms of severe purulent intoxication occur.
Alveolar echinococcosis in all cases is accompanied by liver damage. For a long time, the invasion is asymptomatic. The leading symptom is hepatomegaly due to the development of a tumor-like node of exceptional, “wooden” density. Liver motility is limited due to the development of perihepatitis. The spleen is enlarged in a third or half of patients. A frequent and persistent symptom is jaundice. With a far advanced process, functional liver tests are abruptly disrupted.
Diagnosis of Echinococcosis of the Liver
In the diagnosis of hydatidosis forms of echinococcosis, the patient’s history (living in an area that is endemic for this disease) helps. The decisive role is given to additional research methods. In a general blood test, eosinophilia is often detected (up to 20% and above). Katsoni’s intracutaneous reaction with a sterile echinococcal bladder fluid is used. The mechanism of this test is similar to the reaction to tuberculin in tuberculosis. Katsoni test positive in 75 85% of patients. About 1 year after the death of the parasite, the reaction becomes negative. A more accurate and informative latex agglutination reaction (synthetic polystyrene resin) and indirect hemagglutination reaction. With a survey radiography, one can note the high standing of the dome of the diaphragm or its protrusion, calcifications in the projection of an echinococcal cyst. More detailed information can be obtained by radiography in conditions of pneumoperitoneum. The localization and size of the echinococcal cyst can be judged by the radioisotope hepatoscanning data (at the site of the projection of the cyst, an isotope accumulation defect will be visible). The most reliable and simplest ultrasonic echolocation and computed tomography. Among invasive research methods, laparoscopy and angiography are widespread. With celiacography, an arched displacement of the blood vessels of the liver, characteristic of a volumetric formation, is detected.
For the diagnosis of alveolar echinococcosis, the long-existing “tumor” of the liver of extreme density, hypereosinophilia, liver scans and positive results of allergic tests are important. Of the greatest diagnostic value is the Katsoni reaction with the alveolar antigen.
Treatment of Echinococcosis of the Liver
Self-healing from the hydatidoid form of echinococcus occurs very rarely, which is associated with the death of the parasite and subsequent calcification of its walls. However, in the presence of a large cavity, the threat of suppuration or rupture of the cyst is real. There is not a single drug that has a therapeutic effect on the cystic form of echinococcosis. The high incidence of serious complications of the hydatidosis form of echinococcosis dictates the need for surgical treatment, regardless of the size of the cyst.
The best way to treat echinococcectomy. An ideal echinococcectomy, in which the entire cyst with its chitinous and fibrous membranes is removed without opening the lumen, is rarely used with small sizes of the cyst, its marginal location. With large cysts located in the thickness of the liver tissue, this method is fraught with damage to large vessels and bile ducts. More often, cyst removal with its germinal and chitinous membranes is used after preliminary puncture of the cyst cavity, with the suction of its contents. This technique allows avoiding its rupture and dissemination of the parasite when the cyst is isolated. After removal of the cyst, the fibrous membrane from the inside is treated with a 2% formalin solution and sutured with separate sutures from the inside (capitulation). If it is impossible to suture the cavity, they resort to tamponade with its omentum. When suppuration of the contents of the cyst after the completion of the main stage of the operation, the remaining cavity is drained. With large sizes of the cyst, as well as in the case of calcification of its walls, they resort to marsupialization as a necessary measure (suturing the walls of the cyst into the anterior abdominal wall).
The purpose of the operation is the radical removal of the cyst together with the membranes and their contents without leaving scolexes and blisters in the liver, abdominal or thoracic cavity. The fibrous capsule in most cases is not removed. The volume of surgical interventions depends on the location, size, number and complications of cysts. With regional localization of cysts with calcification, an ideal echinococcectomy is performed together with a fibrous capsule according to A.V. Melnikov, possibly using a CO2 laser.
With multiple echinococcosis and with an edge arrangement of cysts, as well as giant cysts that occupy the entire lobe, an atypical or anatomical liver resection is performed. With single cysts, even with giant ones, with cysts of both halves of the liver and with a festering cyst, the operation of choice is a simultaneous closed echinococcectomy according to A. A. Bobrov and S. I. Spasokukotsky.
To prevent scolex seeding after puncture, the contents of the cyst are removed with echinococcotomas, the fibrous capsule is not removed, the cavity is treated with various antiparasitic agents (2-5% formalin solution, 5% iodine solution, 96% alcohol, etc.), as well as cryotherapy and a defocused CO2 beam. laser.
With subdiaphragmatic localization of the cyst (segments 7-8) and large residual cavity, Delba capitulation is performed or cavity closure according to A.T. Pulatov in combination with omentoplasty or plastic with a diaphragm flap.
When a cyst breaks into the biliary tract, an urgent surgical intervention is performed – choledochotomy with external drainage or closed echinococcectomy, choledochotomy with removal of the membranes and cysts from the biliary tract. The operation is completed by external drainage of the common bile duct, or by the application of choledochoduodenostomy, or endoscopic papillosphincterotomy, transhepatic hepatocholangiostomy due to obstructive jaundice.
Urgent surgical intervention is also performed when a cyst breaks into the abdominal cavity, bronchus, or into the pleural cavity. Closed or half-closed, and exclusively in difficult cases, open (marsupilization) echinococcectomy is performed.
With a gall-bronchial fistula, the fistula is disconnected, the hole in the bronchus is sutured.
With multiple echinococcosis of the liver, the operation is performed before complications develop, first complicated cysts or gigantic cysts are removed, sometimes they operate in 2-3 doses after 2 weeks – 3 months.
Mortality – 1-5%, long-term results are good, relapses – 2-25% and arise due to incomplete removal of daughter blisters, undetected cysts, seeding of the abdominal and chest wounds with cyst contents, repeated infestations, technical errors.
Prevention of Echinococcosis of the Liver
The complex of veterinary and medical measures for echinococcosis is aimed primarily at identifying and eradicating the source of invasion. In accordance with official recommendations, we are talking about reducing the number of guard dogs, their registration, registration and destruction of stray animals.
Veterinary specialists of farms carry out preventive deworming of service dogs from December to April every 45 days, from May to November – every 30 days, the rest – once a quarter. These measures must be carried out with respect to personal dogs. Deworming is carried out at special sites where the separated feces are collected in a metal container and neutralized: (boil for 10 – 15 minutes, pour for 3 hours with a 10% solution of bleach, the soil is treated with a 3% solution of carbathion (4 l per 1 m2 )
To prevent infection of dogs, it is necessary to comply with the rules for slaughtering farm animals and ensure the destruction of affected organs, as well as blocking dogs from entering meat processing plants, slaughterhouses, and cattle burial grounds.
Measures to prevent infection of dogs also include such mandatory recommendations as: raising the veterinary-sanitary level of farms; construction of recycling pits, cattle cemeteries; compliance with the rules of storage and transportation of animal corpses; slaughter of animals only in appropriate places for this, etc.
Medical measures include identification of militant groups invaded by examination (hunters, persons in contact with dogs involved in fur processing, manufacturing of fur products, shepherds) and examination according to clinical indications; deworming and medical observation. Health education is important.
Personal prevention of echinococcosis is to limit contact with dogs, children playing with them, wash their hands thoroughly after contact with animals, before eating after working in the garden, playing in the yard, in the garden, picking mushrooms, do not eat unwashed wild berries Do not drink unboiled water from natural reservoirs.