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Infection with Opisthorchis liver flukes arises from the ingestion of raw or poorly cooked fish contaminated by these parasites. After ingestion, these liver flukes grow to adulthood inside the human biliary duct system. Infections are not known to persist beyond 25–30 years, the lifespan of the parasite.


Ova and parasite (O&P) stool examinations for liver flukes is the only test available for the diagnosis of Opisthorchis infection. More than one stool sample may be needed to identify the eggs. The eggs of Opisthorchis are very similar to those of Clonorchis, another liver fluke, but can be distinguished by microscopic features. Stool examination is unlikely to result in a diagnosis in persons whose only exposure to Opisthorchis took place more than 25–30 years ago (the life span of a liver fluke), as the liver fluke must be living in order to produce eggs. Additionally, cysts containing the parasite can sometimes be detected by ultrasound, CT, or MRI. Serologic testing for Opisthorichis is not useful for patient management and is not available in the United States. In the absence of detection of liver flukes, there is no test available that can determine if liver fluke infection is the underlying cause of cholangiocarcinoma or other hepatobiliary conditions. Routine screening of asymptomatic individuals with a history of travel to endemic countries for liver fluke infection is not recommended.

Risk for Cholangiocarcinoma

There are several parasites that cause liver fluke infections, including Fasciola, Clonorchis, and Opisthorchis. Among these, Fasciola infection is not associated with liver cancer. However, Clonorchis and Opisthorchis, two other liver flukes, are associated with liver cancer, specifically cholangiocarcinoma. Cholangiocarcinoma (CCA) is a rare cancer of the biliary duct system, which is comprised of the gallbladder and bile ducts. Only a small percentage of persons infected with Clonorchis or Opisthorchis develop complications such as cholangiocarcinoma. There are multiple non-parasitic risk factors for CCA, and liver fluke infections are very rarely associated with cases of CCA in the United States. Approximately 90% of patients diagnosed with cholangiocarcinoma in Western countries do not have a recognized risk factor.


Praziquantel, adults, 75mg/kg/day orally, three doses per day for 2 days; the pediatric dosage is the same. Praziquantel should be taken with liquids during meals.


Albendazole* is an alternative drug; the dosage is 10mg/kg/day for 7 days. The pediatric dosage is the same. Albendazole should be taken with food; a fatty meal increases the bioavailability.

* Not FDA-approved for this indication

Oral praziquantel is available for human use in the United States.

Oral albendazole is available for human use in the United States.




Page last reviewed: May 26, 2020