Parasitic liver diseases are a group of heterogeneous diseases caused by parasites and helminths. The most common liver parasitoses are ascariasis, echinococcosis, amoebiasis, opisthorchiasis, etc. Common symptoms include exhaustion, dystrophic changes in the skin and hair, increased fatigue, sleep disorders, bad breath. In diagnostics, duodenal probing, examination of duodenal contents, analysis of feces for helminth eggs, ultrasound, CT, liver scintigraphy are used. Treatment is conservative, consisting in the appointment of an antiparasitic drug (specific or broad-spectrum), or operative.
Parasitic liver diseases are caused by protozoa and worm infestations. The World Health Organization believes that at least 25% of the world’s population is infected with certain parasites. Parasitosis and helminthiasis occupy the fourth place among the diseases that cause the greatest harm to human health. At the moment, there are no studies that would reflect the true incidence of parasitic diseases and helminthiasis in USA. According to experts in the field of infectious diseases and gastroenterology, parasitic infestations can be detected in at least twenty million americans. Given the fact that parasites and worms can persist in the body for many years, the disease often leaves an imprint on life: it causes a delay in growth and development in childhood, worsens the mental abilities of schoolchildren, provokes a decrease in the working capacity and activity of the adult population.
All parasitic liver diseases occur either with protozoal infection or as a result of helminthic invasion. Liver damage in this situation is one of the manifestations of generalized infection. Among protozoal infections, the liver is most often affected by toxoplasmosis, amoebiasis, leishmaniasis, malaria. Helminthiasis is represented by nematodes, cestodoses, trematodes. Nematodoses are caused by roundworms (ascariasis, strongyloidosis, toxocarosis, trichinosis); trematodoses – flukes (fasciolosis, clonorchosis, opisthorchiasis); cestodoses – tapeworms (alveococcosis, echinococcosis).
The variety of clinical manifestations of parasitic liver diseases is due not only to the type of parasite or helminth, but also to their life cycle, the place of introduction into the body, the localization of various life forms, the immune response to the pathogen.
Flukes are usually localized in the bile ducts, gallbladder. Suckers of suckers damage the epithelium of the ducts, in which cysts form, an inflammatory reaction, cholangitis and cholestasis are formed. With fascioliasis, larvae with blood flow penetrate into the liver tissue, then migrate to the biliary tract and there turn into a sexually mature parasite. In the future, helminths damage liver tissue, forming microscopic ulcers in the parenchyma and bile ducts. Ascariasis has a similar pathogenesis of the disease.
With echinococcosis and amoebiasis, volumetric formations form in the liver. Schistosomiasis leads to fibrosis of the liver parenchyma. Infection with malarial plasmodium, trypanosomes, schistosomes leads to a significant increase in the size of the liver, inflammatory process, liver failure.
The main role in the defeat of the hepatic parenchyma is played by pathological immune reactions. Parasites and helminths secrete antigens that provoke excessive immune reactions, leading to significant damage to liver cells and microvessels. Larvae and adults of worms located in the liver tissue secrete a number of enzymes that damage hepatocytes and stimulate the synthesis of fibrin. Chronic persistence of parasites sooner or later leads to liver fibrosis, chronic liver failure.
Echinococcosis occupies a leading place among all parasitic liver diseases. In the vast majority of cases, the right half of the liver is affected, almost half of the patients have several echinococcal cysts. In humans, echinococcosis of the liver can be hydatid (larval stage, cystic form, a person is an intermediate host) and alveococcal. The main host is canids, in whose body the echinococcus matures, and its terminal segments with a huge number of eggs enter the environment, causing human infection by fecal-oral or contact. Once in the stomach, the shell of the eggs dissolves and the worms penetrate through the wall of the stomach or intestines into the blood. With the blood flow, pathogens migrate to the liver, and then to other organs, forming cysts in them (initially – about 1 mm in diameter). The echinococcal cyst of the liver has two shells, the inner one produces the liquid component of the cyst, forms daughter bubbles. The outer shell can calcify, its contents can be suppressed. Huge cysts squeeze the liver parenchyma and blood vessels, biliary tract.
Hydatid echinococcosis. In the first years after infection, echinococcosis may not manifest in any way. The first clinical manifestations usually occur when the cyst reaches a large size – pain in the right side, nausea and vomiting, weakness, emaciation, chronic diarrhea, allergic skin rashes, brittle hair. The size of the liver increases, with a superficial location of the cyst, it can even be scalped. Jaundice develops only when the cyst squeezes the ducts of the liver. A breakthrough of cystic formation into the abdominal or thoracic cavity is possible, accompanied by severe pain, anaphylactic shock (reaction to the absorption of cyst contents). The accumulation of cyst contents is accompanied by liver soreness, fever, and deterioration of the general condition.
Diagnosis of echinococcosis includes collecting anamnesis (contact with a dog), palpation of the liver and detection of an echinococcal cyst. A specific diagnostic method is the Kazoni reaction (positive in 85% of cases), latex agglutination (90%). Ultrasound of the liver and gallbladder, angiography of the abdominal trunk, MRI of the liver and biliary tract, static scintigraphy of the liver, diagnostic laparoscopy will help to visualize the parasite.
Treatment is only operative. Excision of echinococcal liver cysts is performed, formalin is injected into the cyst beforehand and its contents are sucked out. The cyst cavity is sutured tightly. In the future, a non-parasitic cyst, an abscess may form. With small size and marginal position of the cyst, liver resection together with the cyst is possible.
Alveolar echinococcosis. It is a rarer form of parasitic liver disease caused by echinococcus. The causative agent of alveococcosis is distinguished by its larval stage. Infection occurs during the processing of the skins of the main host (fox, etc.), the use of infected products. A feature of alveococcosis is the formation of many small cysts that infiltrate the liver parenchyma, tightly fitting together and forming a tumor-like node in the liver tissue. The vesicles of the parasite are able to germinate into the liver parenchyma, blood vessels, bile ducts, and neighboring organs. Necrosis is formed in the center of the focus of alveococcosis, in the future the alveococcal focus may calcify. The disease should be differentiated with liver cancer, cirrhosis of the liver.
The clinical picture of alveococcosis is similar to the hydatid form of the disease, but has a high frequency of mechanical jaundice. Treatment of liver alveococcosis has certain features. The operation is complicated by the infiltrative growth of parasites, the germination of blood vessels, biliary tract, round ligament of the liver. Usually, the operation is prescribed for significant liver damage, suppuration and breakthrough of cysts. Most often, partial liver resection is performed, the remaining cysts are treated with chemotherapy or formalin, and cryodestruction is performed.
To date, ascariasis of the liver is quite rare. A person becomes infected by eating products infected with ascaris eggs. Getting into the intestine, pathogens penetrate through the intestinal wall into the bloodstream, with the blood flow they enter the liver. Necrosis and microabcesses form in the liver due to the persistence of parasites. In the future, pathogens can migrate through the body, getting into other organs and systems, and turning into sexually mature forms in the intestine.
The main manifestations of ascariasis are cholangitis, cholestasis, liver abscess. There are no specific symptoms of ascariasis. The diagnosis of ascariasis of the liver is established on the basis of the detection of ascariids and their eggs in vomit, feces; it is also possible to visualize helminths with ultrasound, CT of the liver.
Treatment of ascariasis of the biliary tract is only surgical. The use of anti-ascariasis agents for blockage of the bile ducts is contraindicated, as it leads to short-term activation of parasites and their further penetration into the bile ducts and liver parenchyma. To clarify the degree of damage to the ducts during the operation, ERCP is performed. To prevent the persistence of ascariasis, the formation of concretions, it is desirable to perform a cholecystectomy. In the postoperative period, antiascariasis drugs are administered through drains to destroy the remaining helminths.
This parasitic liver disease is quite rare, human infection occurs through raw fish, infected reservoirs. The reproduction of helminth in the bile ducts leads to their expansion. The liver tissue becomes very dense, the enlarged intrahepatic ducts are visible through the liver capsule. The persistence of invasion leads to thickening of the walls of the bile ducts, the formation of rough scarring around them, which resemble cirrhosis of the liver, often lead to perforation of the bile ducts and peritonitis. Blockage of the bile ducts favors stagnation and inflammatory changes in them. Patients with opisthorchiasis often develop liver cancer in the future.
Opisthorchiasis, like other parasitic liver diseases, does not have a specific clinic. Frequent manifestations are enlargement and thickening of the liver, pain in the right hypochondrium, loose stools. In case of infection, the patient is worried about fever, chills, sticky sweat.
The diagnosis is made on the basis of the identification of individuals and eggs of helminths in feces and duodenal juice obtained by probing. The treatment of opisthorchiasis of the liver is surgical, it consists in draining the ducts, introducing antiparasitic drugs into the drains.
The disease is often found in tropical countries. It is characterized by a predominant lesion of the large intestine, dissemination of the pathogen into parenchymal organs. Amoeba cysts enter the human body with contaminated water, fruits and vegetables, and herbs.
Amoebas cause ulcers in the intestine, through which pathogens enter the bloodstream and then into the liver, leading to the formation of liver abscesses in about 10% of cases. The peculiarity of amoebic abscesses is that they do not have capsules, contain molten tissues, coffee-colored pus. The condition of patients is usually very severe, the liver is enlarged and painful. The skin is icteric gray, dry.
In the diagnosis of liver abscess, ultrasound of the hepatobiliary system, liver scintigraphy, CT, puncture biopsy of the liver (in order to detect amoebas) are used. Treatment of amoebiasis is usually complex: anti-amoebic, antibacterial and detoxification drugs. Surgical treatment is carried out with the ineffectiveness of conservative measures, the occurrence of complications.
Prognosis and prevention
The prognosis for parasitic liver diseases depends on many factors: the duration of parasitic invasion, the extent of liver damage, the presence of complications. With a prolonged course of parasitic liver damage with the formation of fibrosis, the development of liver failure, the prognosis is unfavorable.
Prevention of all parasitic liver diseases consists in observing the rules of personal hygiene (washing hands after contact with animals, drinking only boiled water, thoroughly washing vegetables and fruits before eating, carrying out heat treatment of meat and fish), monitoring the condition of reservoirs from which drinking water is taken.