Echinococcal cyst

Echinococcal cyst is a parasitic disease caused by the larval stage of Ehinocococcus granulesus, affecting the liver, lungs, and other organs with a fine capillary network. Humans are intermediate hosts of tapeworms, but horses, camels, pigs, and cows can also be hosts. Definitive hosts include dogs, wolves, cats, foxes, and other predators. In the intestines of the definitive hosts, a sexually mature parasite matures: a worm 4-7 cm long, which attaches to the intestinal wall with the help of a scolex: four muscular suckers and a proboscis with forty hooks. Three segments with different phases of development are attached to the head: a young proglottid, a hermaphroditic proglottid, and a mature proglottid. The mature proglottid, as it matures, is rejected along with the intestinal masses and seeding the environment with 400-800 eggs. Inside each egg there is a six-hooked embryo - an oncosphere.

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How does an echinococcal cyst develop?

Humans become infected by stroking the fur of animals: dogs, cats, cows, horses - or by biting grass blades infected with eggs. Therefore, the disease is more typical for areas with developed cattle breeding or vast forest lands, but can be observed in any zone, since the eggs can also spread with dust. They are very viable: at 0° they live 116 days, and at positive temperatures up to 6-8 months.

Even boiling can last up to 20 minutes. This is despite the fact that one dog can excrete up to 20 thousand parasites. Multiply this figure by 800, and the contamination of the environment will become clear to you. Therefore, endemic zones can form.

Parasite eggs, getting from the environment into the stomach, penetrate the portal venous network and get stuck in the liver capillaries, smaller ones settle in the lung capillaries. These are the two most common localizations. But if the patient has arteriovenous shunts in the lungs due to pulmonary hypertension, the eggs can enter the systemic circulation with damage to any organ and tissue, most often the kidneys, spleen, and brain. They develop slowly, only 5-6 months after infection the larva is formed.

In the liver, an echinococcal cyst is formed from the oncosphere - a larvocyst from 1 to 50 cm, but there are cases of larvocysts with a volume of up to 10 liters. It is filled with a turbid liquid, daughter bubbles float inside, they may contain granddaughter bubbles - hydatid sand. In the lungs, the bubbles are smaller in volume and do not contain hydatid sand, so they are called "acephalocysts". A dense fibrous capsule is formed around the larvocyst.

The parasite causes a very complex pathogenesis of the disease, but it is not needed in full for clinicians. It is necessary to remember the main points: the echinococcal cyst is allergen-active, forms polyallergy, eosinophilia and a complex of specific antibodies that allow immunoreactions to detect the disease in the initial stages. The echinococcal cyst causes atrophic compression of tissues with complete or partial dysfunction, which can be detected by 4 laboratory tests. Rupture, opening it with the contents getting on the peritoneum causes the deepest, immediate anaphylactic shock, which is almost impossible to suppress. Immunity is not formed. Reinfection is possible. But the developed echinococcal cyst plays the role of a monopolist. Other bubbles develop extremely rarely with it, unlike alveococcosis. The clinic is polymorphic. During the course, 3 stages are distinguished;

1. Latent (asymptomatic) - from the moment of penetration of the oncosphere until the first symptoms appear. No complaints. Echinococcal cyst is detected accidentally during abdominal operations. Less often, and at a later period, when the echinococcal cyst reaches 3-5 mm, it can be detected by ultrasound or computed tomography.
2. Symptomatic, when symptoms of dysfunction of the organ of localization appear due to compression of the organ parenchyma itself and surrounding tissues. General symptoms: weight loss, weakness, urticaria, blood eosinophilia. Local manifestations are very weakly expressed. When localized in the liver: pain, a feeling of heaviness in the right hypochondrium, with external localization, a tumor-like elastic formation is palpated, a symptom of hydatid tremor is revealed (a palm with spread fingers is placed over the tumor-like formation, when strongly tapping on the third finger, a characteristic tremor is revealed). If the echinococcal cyst is localized in the lung: chest pain; persistent dry cough, hemoptysis.
3. Complications: the echinococcal cyst becomes purulent, calcifies, breaks through into the abdominal or pleural cavity. This is accompanied by pain syndrome, anaphylactic shock, formation of purulent fistulas, ascites, jaundice, liver failure, respiratory failure, pulmonary atelectasis, etc.

The duration of each stage cannot be determined, most often it proceeds asymptomatically for up to 5 years, unnoticed for 3-5 years. In most cases it is detected only when complications develop.

True relapses are observed extremely rarely, after a long time after radical surgery. False relapses caused by violation of radicality, leaving sections of the wall, seeding with daughter bubbles are observed a year after surgery in 11.8% of cases.

How is an echinococcal cyst recognized?

Echinococcal cyst is diagnosed based on the epidemiological history, clinical picture, and comprehensive clinical examination data: X-ray, ultrasound, functional and laboratory, magnetic resonance, etc. X-ray methods are most effective in case of calcification of the bladder, since they reveal a calcification ring, characteristic only of echinococcus. In the lungs, an echinococcal cyst is detected by a fibrous calcification ring, its shape changes at different phases of breathing - Nemenov's symptom; a strip of gas is often traced between the bladder membrane and the fibrous capsule - Velo-Petenil's symptom. If an echinococcal cyst of the lung ruptures, the Garcia-Sogers symptom is formed radiologically - characteristic shadows are formed, having the appearance of a "floating lily" or "floating ice floe", which are caused by the shadow of the bladder wall and the shadow of the membrane.

Due to possible seeding, an echinococcal cyst should not be punctured. But if a puncture is made by mistake, an urgent laboratory study is carried out (the presence of chitin, scolex hooks) and an urgent surgical intervention is immediately performed. The Katsoni reaction can also be carried out with the puncture: 0.1 ml of saline is injected intradermally into one forearm; 0.1 ml of sterile bladder puncture into the other - a reaction occurs in the form of hyperemia, itching, edema. Its reliability is up to 50%, so it is practically not used;

Basically, two specific reactions are used;

1. Fishman's latex agglutination immunological reaction. Its reliability is 96.3%. It is safe for the patient; can be used in case of relapses. It is mainly used in mass studies in endemic foci.
2. Simultaneously with latex agglutination, serological enzyme-immunological reactions with specific antigens are also carried out. This reaction reveals invasion already on the 7th-21st day after infection. It helps differentiate echinococcal cysts and alveococcosis.

Alveococcosis is a multilocular echinococcus caused by a helminth: Ehinokokkus alveolaris. Its structure and invasion are similar to hydatid echinococcus. It is localized mainly in the liver. The final host is a fox, arctic fox, wolf, dog, cat. Man is an intermediate host.

Infection occurs: when skinning, shaking them out indoors, when in contact with infected animals, when eating infected berries. It is mainly observed in taiga regions, more often among hunters. The eggs are very tenacious, even at minus 40 degrees they survive for a year.

The development of the disease is characterized by the same 3 stages as with hydatidosis echinococcus. The clinical picture is also expressed in the development of liver failure: weakness, weight loss, jaundice; but, unlike cirrhosis, there is never ascites. The liver is initially enlarged and very dense - according to Lyubimov - "iron liver" - later it becomes lumpy to the touch.

Complications differ from hydatid echinococcosis: it grows into neighboring organs, gives metastases to the lungs, brain. The parasitic tumor is subject to decay in the center with sequestration, there may be a breakthrough into the abdominal and pleural cavities, hepatic ducts and bronchi.

The diagnosis is rarely made at early stages of development - 15% of cases, mainly during mass examinations of the population. It is more often detected in the late period during examination of the liver to determine the cause of liver failure; On survey radiographs, small focal calcifications - "lime splashes". More reliable data are obtained with computed tomography and laparoscopy.