Opisthorchiasis - Overview

Opisthorchiasis (Latin: opisthorchosis, English: opisthorchiasis, French: opisthorchiase) is a natural focal biohelminthiasis with a fecal-oral mechanism of transmission of the pathogen, characterized by a long course and predominant damage to the hepatobiliary system and pancreas, a disease caused by the penetration into the human body and the development in it of a mature form of helminth - the cat fluke

ICD-10 code

B66.0. Opisthorchiasis.

Epidemiology of opisthorchiasis

Opisthorchiasis is widespread on the Eurasian continent. It is registered in a number of countries in Eastern and Central Europe. In Russia and the CIS countries, the most extensive foci of infection are found in Western Siberia, Northern Kazakhstan (the Ob and Irtysh basins), Perm and Kirov regions and the basins of the Kama, Vyatka, Dnieper, Desna, Seim, Northern Donets, and Southern Bug rivers. The most tense situation is noted in Western Siberia, where the largest Ob-Irtysh foci of invasion are located.

The source of infection is people infected with opisthorchiasis, as well as domestic animals (cats, pigs, dogs) and wild carnivores whose diet includes fish.

Human infection occurs by eating raw or unprocessed fish that has been heated, frozen, or salted and contains viable metacercariae.

The natural susceptibility of people to opisthorchiasis is high. The highest incidence rates are registered in the age group from 15 to 50 years. Men are slightly more often affected. Infection usually occurs in the summer-autumn months. Repeated cases of infection after recovery are often observed. Immunity is unstable. The risk group is represented by new settlers who have arrived in endemic areas and thoughtlessly adopt local traditions of eating unprocessed fish.

The infestation rate of the rural population in the Middle Ob region reaches 90-95%, and children in their first year of life are often infected. By the age of 14, the infestation rate of children with this helminthiasis is 50-60%, and among the adult population it is almost 100%.

Opisthorchiasis of lower intensity is found in the basins of the Volga and Kama, Ural, Don, Dnieper,

Northern Dvina, etc. Foci of opisthorchiasis caused by O. viverini are found in Thailand (in some provinces of which up to 80% of the population is affected), as well as in Laos, India, Taiwan, and a number of other countries in Southeast Asia. In non-endemic areas, imported cases of opisthorchiasis and even group diseases are recorded. The infection factor in such cases is imported infected fish.

With opisthorchiasis, many infectious diseases occur in more severe forms. Patients with opisthorchiasis who have had typhoid fever are 15 times more likely to develop chronic salmonella carriage.

O. felineus develops with a triple change of hosts: the first intermediate (mollusks), the second intermediate (fish) and the final (mammals). The final hosts of the parasite include humans, cats, dogs, pigs and various species of wild mammals whose diet includes fish (fox, arctic fox, sable, ferret, otter, mink, water rat, etc.).

From the intestines of the final hosts, fully mature opisthorchis eggs are released into the environment. Parasite eggs that fall into a body of water can remain viable for 5-6 months. In the water, the egg is swallowed by a mollusk of the genus Codiella, in which a miracidium emerges from it, which then turns into a sporocyst. Rediae develop in it, then penetrate the liver of the mollusk, where they give birth to cercariae.

All larval stages develop from germ cells parthenogenetically (without fertilization). During the transition from one stage to the next, the number of parasites increases.

The development time of parasites in the mollusk, depending on the water temperature, can range from 2 to 10-12 months. Upon reaching the invasive stage, cercariae exit the mollusk into the water and, using the secretion of special glands, attach to the skin of fish of the carp family (tench, ide, dace, carp, bream, barbel, roach, etc.). Then they actively penetrate the subcutaneous tissue and muscles, lose their tail and, after a day, encyst, turning into metacercariae, the dimensions of which are 0.23-0.37 x 0.18-0.28 mm. After 6 weeks, metacercariae become invasive, and the fish containing them can serve as a source of infection for the final hosts.

In the intestine of the definitive host, under the influence of duodenal juice, the larvae are released from the cyst membranes and migrate to the liver via the common bile duct. Sometimes they can also get into the pancreas. After 3-4 weeks from the beginning of infection of the definitive hosts, the parasites reach sexual maturity and after fertilization begin to release eggs. The lifespan of the cat fluke can reach 20-25 years.

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What causes opisthorchiasis?

Opisthorchiasis is caused by Opistorchis felineus (cat fluke) belongs to the type of flatworms (trematodes), class of flukes. It has a flat elongated body 8-14 mm long and 1-3.5 mm in diameter; equipped with two suckers - oral and abdominal. Opisthorchis are hermaphrodites. The eggs are pale yellow, almost colorless, with a smooth double-contour shell that has a lid on a slightly narrowed pole and a small thickening at the opposite end. The size of the eggs is 23-24x11-19 µm.

The pathogen has a complex development cycle. In addition to the final hosts, it has two intermediate and an additional host. In definitive (main) hosts, the helminth parasitizes in the sexually mature stage of its development. From the bile ducts, gall bladder and pancreatic ducts of humans and carnivorous mammals (cats, dogs, foxes, arctic foxes, sables, wolverines, domestic pigs, etc.), the parasite eggs penetrate the intestines along with bile and then enter the environment.

Pathogenesis of opisthorchiasis

After eating the infested fish, the metacercariae enter the stomach and duodenum, and after 3-5 hours they reach the intrahepatic bile ducts - their main habitat in the body of the final host. In 20-40% of infected individuals, opisthorchiasis is found in the pancreatic ducts and gall bladder. During migration and further development, they secrete enzymes and metabolic products that have a sensitizing and direct toxic effect on the body.

The worm that causes opisthorchiasis was discovered in humans by K.N. Vinogradov in 1891 and was called the Siberian fluke by him, since the worm has two suckers. A sexually mature worm is 4 to 13 mm long and 1 to 3 mm wide. The head of the parasite has an oral sucker. The body of the worm has a second abdominal sucker. A sexually mature worm can release up to 900 eggs per day. The development cycle of the parasite includes its stay in the body of two intermediate and one final host. When opisthorchiasis eggs fall into water, they are swallowed by the mollusks Bithynia inflata. In the intestines of this mollusc, a larva, a miracidium, emerges from the egg. The latter undergoes several stages in the body of the mollusc and turns into rediae, from which cercariae eventually emerge. Cercariae leave the body of the mollusk, enter the water and penetrate through the scales into the muscle of carp fish. There they turn into metacercariae and remain until the fish is eaten by the final host. The final hosts of opisthorchis are humans, cats, dogs, wolves, foxes and pigs. Six weeks after infection of the final hosts, sexually mature worms begin to release eggs into the environment.

Mature opisthorchiasis parasitizes in the ducts of the liver and pancreas. The degree of parasitic invasion can vary - from several individuals to several thousand. Opisthorchiasis occurs in two phases - acute and chronic. The acute phase of opisthorchiasis lasts from 4 to 6 weeks after infection. It occurs as an acute allergic disease with sensitization of the body by the products of the vital activity of opisthorchiasis. The immune reaction in the acute stage of opisthorchiasis leads to damage to the mucous membrane of the habitats of the parasites, the walls of blood vessels and the nervous system. The chronic stage of the disease can last for years and lead to serious changes in the habitat of the parasites. Opisthorchiasis, parasitizing in the ducts of the liver and pancreas, has a mechanical, toxic and infectious-allergic effect on the walls of the bile ducts and pancreatic ducts. Mechanical damage to the mucous membrane of the ducts by the hooks and suckers of parasites leads to its trauma and the addition of a secondary infection, which causes productive inflammation of the duct walls.

Inflammatory and sclerotic changes in the walls of the ducts are most pronounced and clinically significant in the cystic duct and major duodenal papilla and often lead to their sharp narrowing or obliteration. These changes lead to the development of biliary hypertension, expansion of the intrahepatic ducts and the appearance of cholangioectasis under the Glisson capsule of the liver.

In the liver parenchyma and pancreas, sclerotic processes also occur, ultimately leading to the development of liver cirrhosis and chronic pancreatitis. All the described morphological manifestations of opisthorchiasis invasion in combination with secondary infection lead to the development of a number of complications requiring surgical intervention.

What are the symptoms of opisthorchiasis?

Opisthorchiasis has an incubation period of 2-6 weeks after eating infected fish. Opisthorchiasis is characterized by a polymorphic clinical picture.

Opisthorchiasis does not have a single classification. An acute phase of invasion is distinguished, which can be asymptomatic or erased in native inhabitants of endemic regions during reinvasion or superinfection. A clinically expressed form of the acute phase is observed in persons who arrived in an endemic region. The chronic phase of the disease in the absence of symptoms of the acute phase is assessed as primary-chronic: if it is preceded by an acute phase - as secondary-chronic. Organ lesions (biliary tract, pancreas, stomach and duodenum) can persist even after the body is freed from opisthorchiasis, so some authors distinguish a residual phase of the disease.

In the chronic stage of opisthorchiasis, patients usually complain of constant aching pain in the liver area, which intensifies on an empty stomach, a feeling of heaviness in the right hypochondrium, and dyspeptic symptoms. As complications develop, the nature of the complaints changes.

The most common complication of opisthorchiasis is strictures of the cystic duct. Clinically, they manifest as obstructive cholecystitis with pain in the right hypochondrium, positive Murphy and Ortner symptoms, and an enlarged gallbladder. Purulent cholangitis and mechanical jaundice are diagnosed in 10% of patients. In acute obstructive cholecystitis, severe pain in the right hypochondrium radiating to the right shoulder and scapula, vomiting, and symptoms of purulent intoxication are observed. Palpation reveals sharp pain and symptoms of peritoneal irritation in the gallbladder area, the bottom of which can often be palpated. About half of these patients are treated surgically.

The main symptom of strictures of the major duodenal papilla, in addition to pain, is considered to be icteric coloration of the sclera and skin, acholic feces and dark urine. With concomitant cholangitis, hectic temperature and chills with profuse sweating are noted. It should be noted that with strictures of the distal part of the common bile duct and the major duodenal papilla, jaundice can occur without an attack of pain. An enlarged gallbladder in this case simulates the Courvoisier symptom, characteristic of tumors of the head of the pancreas. In severe cases with prolonged opisthorchiasis invasion, sclerosing cholangitis sometimes occurs, characterized by progressive jaundice with hepatosplenomegaly and the development of biliary cirrhosis of the liver.

Liver cysts of opisthorchiasis genesis are not detected very often, they are usually located at the edges of the organ, more often in the left lobe and are of a retention nature. Clinically, they manifest as pain in the right hypochondrium in patients with a long-term course of the disease. When palpated, an enlarged, lumpy, slightly painful liver is determined.

Liver abscesses in opisthorchiasis are a complication of purulent cholangitis. Clinically, they are manifested by the severe condition of patients, severe pain in the right hypochondrium and hectic temperature. The liver is enlarged and painful to palpation. Opisthorchiasis abscesses are classified as cholangiogenic abscesses. They are often multiple.

Opisthorchiasis pancreatitis can be both acute and chronic. Its manifestations do not differ significantly from pancreatitis caused by other reasons.

How is opisthorchiasis diagnosed?

The diagnosis of opisthorchiasis is established on the basis of clinical, epidemiological and laboratory data: consumption of thermally untreated, lightly salted fish in endemic regions; fever, toxic-allergic syndrome; leukocytosis and eosinophilia in the blood; in the chronic phase - symptoms of cholecystopancreatitis, gastroduodenitis.

Opisthorchiasis is diagnosed using EGDS, cholecystography, duodenal intubation, ultrasound of the abdominal organs, and determination of the acidity of gastric juice.

Laboratory and instrumental studies

Among the laboratory methods of research in the diagnosis of opisthorchiasis, the following are considered priority: coprological examination, duodenal sounding data and immunological reactions. In immunological tests, a precipitation reaction in gel is carried out, but this reaction can also be positive in other helminthiases. Coprological examination reveals the presence of opisthorchis eggs in the feces. In this case, coprological examination should be carried out several times. In duodenal sounding, parasite eggs are detected in the obtained bile using microscopy. They are especially numerous in portion "B".

Ultrasound reveals a large gallbladder and stricture of the cystic duct. This is usually combined with dilation of the intrahepatic bile ducts and periductal fibrosis. With stricture of the common bile duct, its dilation is noted and cholangioectasis is detected. Opisthorchiasis cysts and liver abscesses are also quite clearly determined by ultrasound. During this study, the presence of pericholedocheal lymphadenitis is also confirmed.

Fibrogastroduodenoscopy reveals a picture of duodenitis and fibrin deposition on the duodenal mucosa in the form of "semolina". Retrograde cholangiopancreatography reveals the presence of bile duct strictures, cysts, liver abscesses and bile duct dilation, as well as cholangioectasis. A characteristic feature of bile duct strictures in opisthorchiasis is their rather large length.

During laparotomy, dilation of the bile ducts is noted, especially on the lower surface of the liver, mainly in the left lobe of the organ, the presence of cholangioectasis, a large distended gallbladder, dilation of the extrahepatic bile ducts and enlarged inflamed pericholedochal lymph nodes. During intraoperative cholangiography in the case of opisthorchiasis invasion, a massive exit of parasites from the bile ducts is noted, especially after the introduction of iodine-containing drugs into the ducts.

Differential diagnostics

In case of mechanical jaundice with the presence of a distended gallbladder, a differential diagnosis of opisthorchiasis with tumors of the head of the pancreas should be carried out. This is especially important in the presence of pseudotumorous opisthorchiasis pancreatitis.

Living in an endemic area, eating raw and dried fish, coprological examination, duodenal intubation and immunological reactions are the guiding signs for the correct diagnosis of opisthorchiasis.

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Example of diagnosis formulation

Acute (chronic) opisthorchiasis. Complications: opisthorchiasis obstructive cholecystitis, stricture of the distal common bile duct

With or without jaundice, opisthorchiasis liver cyst, opisthorchiasis liver abscess, opisthorchiasis pancreatitis acute or chronic (painful, pseudotumorous, pancreatic cyst).

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Screening

Screening examination should cover all patients seeking medical care in endemic areas and include coprological, immunological and ultrasound examinations.

How is opisthorchiasis treated?

The goal of treatment is deworming and elimination of disorders caused by complications of opisthorchiasis. Deworming is carried out on an outpatient basis, and complications of opisthorchiasis serve as an indication for hospitalization in a surgical hospital.

Opisthorchiasis is treated comprehensively, individually, taking into account concomitant diseases. Patients are hospitalized according to clinical indications. A gentle regimen is prescribed, diet No. 5 for 6 months.

Drug treatment

For deworming in opisthorchiasis, a one-day course of treatment with biltricid (praziquantel) is used. The course of treatment requires a dose of 60 mg of the drug per kilogram of the patient's body weight. After a course of preliminary hepatotropic therapy, the patient takes the required dose of the drug in 6 doses during the day. The effectiveness of such deworming reaches 80-90%. The next day, control duodenal intubation is performed.

The drug of choice is praziquantel or its domestic analogue azinox. Opisthorchiasis is usually treated on an outpatient basis (except for patients with pronounced symptoms of the acute phase, severe organ damage, toxic-allergic manifestations). In the acute phase, therapy begins after the fever has been relieved, intoxication and allergic symptoms have been eliminated.

Surgical treatment

Surgical treatment is used only when complications of opisthorchiasis invasion develop. It includes cholecystectomy, interventions on extrahepatic bile ducts and operations for complications of the liver and pancreas.

The opinion of some surgeons that in case of opisthorchiasis cholecystitis it is necessary to limit oneself to sanitation of the gallbladder by means of cholecystostomy has no sufficient grounds. The groundlessness of this position is proved by the pronounced impairment of the contractile function of the gallbladder during its opisthorchiasis invasion. In case of opisthorchiasis cholecystitis the gallbladder practically does not function and turns into a source of chronic infection. In addition, in 90% of cases opisthorchiasis cholecystitis is accompanied by gallbladder stones. Also, in the presence of gallbladder stones it is impossible to effectively combat cholangitis, which is detected in 80% of cases. Sanitation of the bile ducts through cholecystostomy is impossible due to strictures of the cystic duct. Therefore, in cases of opisthorchiasis cholecystitis, cholangitis and strictures of the extrahepatic bile ducts, cholecystectomy is considered the operation of choice.

The condition of the extrahepatic bile ducts is necessarily assessed using intraoperative cholangiography and choledochoscopy. In the presence of a stricture of the distal common bile duct or large duodenal papilla, the passage of bile into the intestine is necessarily restored by applying a choledochoduodenoanastomosis or choledochojejunostomy on the Roux-en-Y loop of the intestine. Endoscopic papillosphincterotomy for opisthorchiasis strictures is rarely performed, due to the fact that the narrowing of the ducts in this disease is usually prolonged and cannot be eliminated by intervention on the terminal section of the common bile duct.

Formation of biliodigestive anastomoses in opisthorchiasis strictures should be combined with supra-anastomotic drainage for subsequent sanitation of extrahepatic bile ducts. Daily rinsing of the ducts with iodine-containing solutions and antibiotics in the postoperative period allows eliminating cholangitis and in 90% of cases ridding patients of opisthorchiasis invasion without additional therapy.

In case of opisthorchiasis liver cysts, liver resection is performed, and in case of opisthorchiasis liver abscesses, their drainage is performed. Single abscesses can be removed by resection of the affected parts of the liver.

In case of opisthorchiasis cysts of the tail and body of the pancreas, resection of the affected sections with the cyst is performed. In case of head cysts, resection of the anterior wall of the cyst and cryodestruction of the remaining walls are performed.

Possible postoperative complications. With radical surgery with restoration of bile passage into the intestine, the probability of complications is low. After operations on cysts, biliary peritonitis and postoperative pancreatitis may develop. The use of cryotechnics reduces the risk of pancreatitis. Mortality after cholecystectomy and operations on the bile ducts is 2-3%.

Further management

After operations on the gall bladder and bile ducts, the patient is unable to work for three to four weeks. After interventions on the liver and pancreas, the period of incapacity is two months, and easier working conditions are necessary for 6-12 months.

How to prevent opisthorchiasis?

To prevent opisthorchiasis, you should not eat uncooked carp fish.

What is the prognosis for opisthorchiasis?

In the absence of bacterial complications, opisthorchiasis usually has a favorable prognosis. A serious prognosis is with the development of purulent processes in the bile ducts, biliary peritonitis and acute pancreatitis: unfavorable with the development of cholangiocarcinoma or liver cancer.