What do liver flukes look like

In people, adult flukes release eggs through the bile ducts into the intestine. Fluke eggs are passed in stool feces. In the environment, the eggs are ingested by snails.

Inside the snail, the eggs go through several stages to develop into an immature form of the fluke that has a tail and can swim cercariae. The cercariae penetrate the skin of a freshwater fish and form cysts in the tissues of the fish. People are infected when they consume the cysts in raw, undercooked, salted, pickled, or smoked freshwater fish, or sometimes freshwater shrimp.

The larvae travel back up the intestine into the bile duct and then into the liver or gallbladder. After the cysts of Fasciola hepatica or Fasciola gigantica are swallowed, they reach the intestine and release immature larvae.

The larvae move through the wall of the intestine into the abdominal cavity and liver, then to the bile ducts.

There, they develop into adult flukes, which produce eggs. Eggs are passed in stool. In water, the eggs release larvae, which penetrate snails. Infected snails release immature flukes cercariae , which form cysts on watercress and other water plants. At first, liver flukes may cause no symptoms, or depending on the type and severity of the infection, they may cause fever, chills, abdominal pain, liver enlargement, nausea, vomiting, and hives.

Fasciola flukes are more likely to cause these symptoms. Over time, if adult flukes block enough of the bile duct inside or outside the liver, people may develop yellowing of the skin and whites of the eyes jaundice Jaundice in Adults In jaundice, the skin and whites of the eyes look yellow. Jaundice occurs when there is too much bilirubin a yellow pigment in the blood—a condition called hyperbilirubinemia. See also Overview Sometimes the flukes damage the liver, causing scarring fibrosis Fibrosis of the Liver Fibrosis is the formation of an abnormally large amount of scar tissue in the liver.

It occurs when the liver attempts to repair and replace damaged cells. Many conditions can damage the liver Other complications include bacterial infections of the bile ducts, gallstones, and pancreatitis. Occasionally, liver flukes infect the wall of the intestine, the lungs, the skin, or the throat.

Years later, infected people may develop cancer of the biliary ducts Tumors of the Bile Ducts and Gallbladder Tumors, both noncancerous and cancerous, within the bile ducts or gallbladder are rare. These cancers This cancer has occurred in Vietnam veterans, who may have eaten raw or undercooked fresh water fish carrying liver flukes while serving in Southeast Asia. Whether liver fluke infection contributed to the cancer's development in Vietnam veterans is uncertain.

Doctors diagnose Clonorchis , Opisthorchis , or Fasciola infections when they see fluke eggs in a person's stool feces or in the contents of the person's intestines.

However, finding eggs in stool may be difficult. In the early stages of Fasciola hepatica infection, blood tests can be done to check for antibodies to the flukes. There are no symptoms in the early stages, but they develop as the…. Learn about the hepatitis C antibody test, which is used to detect when someone has had the hepatitis C virus. What do the results mean? Bilharzia, or schistosomiasis, is a parasitic disease that can result in serious damage to the internal organs.

A river fluke or worm that lives in…. Yellow fever is a hemorrhagic fever. In severe cases it causes a high fever, bleeding into the skin and the death of cells in the liver and kidneys.

The liver is the largest solid organ in the human body. It performs essential tasks, including detoxification, protein synthesis, and the….

Everything you need to know about liver fluke. Medically reviewed by Jill Seladi-Schulman, Ph. Adult flukes settle in the small intrahepatic bile ducts and then they live there for years. The long-lived flukes cause long-lasting chronic inflammation of the bile ducts and this produces epithelial hyperplasia, periductal fibrosis and bile duct dilatation.

The vast majority of patients are asymptomatic, but the patients with heavy infection suffer from lassitude and nonspecific abdominal complaints. The complications are stone formation, recurrent pyogenic cholangitis and cholangiocarcinoma.

Approximately 35 million people are infected with liver flukes throughout the world and the exceptionally high incidence of cholangiocarcinoma in some endemic areas is closely related with a high prevalence of liver fluke infection. Considering the impact of this food-borne malady on public health and the severe possible clinical consequences, liver fluke infection should not be forgotten or neglected. The general term 'fluke' refers to flat fish, for example, rays in the sea or leeches in fresh-water.

Like leeches, liver flukes are flat helminthes or platyhelminth, of the class trematoda, and they reside in the human bile ducts Fig. It is one of the most important food-borne diseases. The epidemiology of the infections is determined by food and ecological factors and it is strongly influenced by poverty and pollution in some areas and by the traditions of food intake in other areas.

Endoscopy reveals "rayfish-like" or "leech-like" flat worm moving within lumen, and it has whitish-yellow ventral sucker at tapered head portion of worm. The disease is generally dormant and the infected people are asymptomatic, except for the patients with very heavy infections. However, the long-lived flukes cause chronic inflammation of the bile ducts, leading to suppurative cholangitis, formation of bile duct stone and the development of cholangiocarcinoma.

In this article, we review the parasitology, epidemiology and the clinical findings and complications of liver fluke infection, and particularly the pathogenesis of cholangiocarcinoma in association with liver flukes. Clonorchiasis and opisthorchiasis are trematodiases that are caused by chronic infection of the human liver flukes in the biliary tree. The three species of flukes, Clonorchis sinensis , Opisthorchis viverrini and Opisthorchis felineus are closely related trematodes that have similar life cycles and they cause the same pathophysiology to the biliary tract.

The flukes differ in their geographic distribution and morphology. The adult fluke of Clonorchis sinensis is a willow-leaflike, flat, flabby worm that lives in the biliary tree Fig.

The size of the parasite ranges from 8. Humans are infected when ingesting uncooked fresh water fish infested with metacercariae. The larvae excyst in the stomach, migrate to the ampulla of Vater, ascend into the bile ducts and live there for years.

Usually they reside in the medium sized or small intrahepatic bile ducts, but they may also live in the extrahepatic duct, gallbladder and the peripheral pancreatic branch ducts.

Intraductal flukes cause mechanical obstruction, inflammation, epithelial adenomatous hyperplasia and periductal fibrosis 2 - 5 Fig. One adult fluke lays eggs each day and the eggs are excreted through the bile ducts and feces 2. The cycle recirculates via eating of raw fresh-water fish. Photomicrograph of rabbit bile duct that was experimentally infected with C. The adult fluke of Opisthorchis is very similar to C.

As compared to C. As the endemic areas of Opisthorchis are different from Clonorchis , the first and second intermediate hosts are slightly different. However, the pathophysiology, clinical manifestations and imaging findings of O. The clinical symptoms depend on the degree of infection and the presence of complications. The vast majority of patients are asymptomatic. In patients with severe infection, the clinical signs and symptoms include lassitude Fig.

Jaundice is due to the mechanical obstruction caused by a multitude of flukes in the bile ducts in patients with a heavy infection, or it is due to bile duct obstruction caused by stone, cholangitis or cholangiocarcinoma as a late complication of chronic infection.

The public health impact and economic impact are considerable in terms of the morbidity, the loss of productivity and the absenteeism of heavily infected people 1. He had been previously admitted 10 years ago because of jaundice and he was diagnosed with clonorchiasis and treated with praziquantel. Five years later, he had cholecystectomy for gallbladder stones and cholecystitis. Since then, he has been suffering from general weakness and lassitude. He has been eating raw fresh-water fish frequently for more than 12 years because he believed raw fish was helpful for his health.

CT shows mild dilatation of small intrahepatic bile ducts up to periphery of liver without dilatation of large bile ducts, which is characteristic for clonorchiasis. The geographic distribution of liver flukes is largely in Asia and Eastern Europe.

Endemic areas of Clonorchis sinensis include east Russia and Manchuria, South Korea, mainland China except the northwest , Taiwan and northern Vietnam 1 - 3 , whereas the endemic areas of Opisthorchis viverrini include Laos and northeast Thailand 1 - 4.

The endemic areas of Opisthorchis felineus include Eastern Europe and the former U. People living along rivers are prone to infection by flukes because they have a habit of eating uncooked fresh-water fish.

In the North American countries where many Asian immigrants are living, there are some people infected with C. It is estimated that about 35 million people are infected throughout the world 1 - 3. In China, there are two principal endemic areas, namely southern China and Manchuria. There are about 8. In northern Thailand and low land Laos, there is a long tradition of eating raw fresh-water fish and salt-fermented fish. Cyprinoid fish, which are fresh water fish, are an important source of protein in these areas 1.

In a community in Khon Kaen, the overall prevalence of O. The tradition of eating raw or undercooked fish products is the reason for this high prevalence The prevalence rate of C. This high prevalence rate is because the patients included in the study were hospitalized, aged patients including long-lasting infection as well as healed infection.

Bile stagnation due to mechanical obstruction caused by epithelial hyperplasia and the profuse mucin caused by goblet cell hyperplasia make the bile ideal for stone formation. The presence of worms and ova play a role as the nidus for the formation of stones 2. Bacterial deconjugation of bilirubin-glucuronide with formation of insoluble bilirubin during bouts of cholangitis may precipitate formation of bilirubin stone Not infrequently, C.

In a hospital-based study based on sampling of bile, C. In another hospital based case-control study in Korea, radiologic evidence of C. Photomicrograph of C.

MR cholangiogram shows severe dilatation of posterior inferior segmental branch of right hepatic lobe and it is filled with multiple stones. There is no definite intraductal mass. Note mild dilatation of the other segmental bile ducts. Microphotographs show several adult C. Note micropapillary growth of atypical biliary epithelium arrows in D. Biliary intraepithelial neoplasia is microscopic structure and this is not visible macroscopically or on radiological images.

Recurrent pyogenic cholangitis is the most common complication of liver fluke infection. Acute suppurative cholangitis may be caused by blockage of the extrahepatic bile ducts by masses of dead worms, ova and mucin, and this in turn results in ascending cholangitis 2 , When the bile flow is hampered by the presence of flukes per se, their ova, the excreta of the flukes and mucin, then ascending bacterial infection usually follows.

The bacteria is Escherichia coli in the majority of patients With repeated suppurative infection, the bile duct is filled with pus and the liver flukes die because of an unfavorable living environment, and the dead flukes are expelled through the ampulla of Vater 2. The egg positive rate is significantly decreased in patients with suppurative cholangitis, compared to that of the uninfected patients in the same cohort Hepatocellular carcinoma and cholangiocarcinoma are the two most common primary malignant tumors arising in the hepatobiliary system.

While hepatocellular carcinoma is well recognized globally, cholangiocarcinoma has received much less attention probably because it is far less common in western countries. Cholangiocarcinoma is relatively uncommon in western countries with the incidence being 0.

On the other hand, the incidence of cholangiocarcinoma in Asian countries is much higher. The incidence of cholangiocarcinoma in Japan and Singapore is 2. The exceptionally high incidence of cholangiocarcinoma in Thailand and Korea is strongly related with the high prevalence of opisthorchiasis and clonorchiasis. The evidence for the association between liver fluke infection and bile duct malignancy includes hospital based case-control studies and population-based studies that have correlated the incidence of bile duct cancer with the prevalence of liver fluke infection in various geographic areas.

In a hospital-based case series in Thailand, an unusually high incidence of cholangiocarcinoma was observed on autopsy and on the biopsy materials taken from patients with O.

The ratio between hepatocellular carcinoma and cholangiocarcinoma without opisthorchiasis was , whereas the ratio was reversed among those with fluke infection There have been several cross-sectional studies regarding the incidence of cholangiocarcinoma in patients with O.

In a population based study in an endemic area of northern Thailand, the age standardized incidence rates of cholangiocarcinoma in the year were In another prospective case-controlled study, seven of patients with O.

Transverse sonogram of middle age man who was included in sonographic survey in village near Vientiane, Laos shows 3. CT image of same patient showed mass, which was consistent with cholangiocarcinoma not shown. In South Korea, there has been a report revealing a six fold increased incidence of cholangiocarcinoma in the Pusan area in the southern part of Korea where the prevalence of C. More recently, a case controlled study in the same area revealed that identification of C. In another hospital based control study in Korea, there was evidence that C.

In patients with cholangiocarcinoma, there was evidence of C. Intraductal papillary neoplasm of the bile duct is known to be a premalignant condition and it is often associated with mucin over-production.

There have been a few recent papers revealing that the disease was related with C. Suh et al. Jang et al. The incidence of cholangiocarcinoma in endemic areas in China and its relation with C.