Ova and parasite (O&P) stool examinations for liver fluke eggs is the only available way to diagnosis 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 alive in order to produce eggs. Additionally, cysts containing the parasite can sometimes be detected by ultrasound, CT, or MRI. Testing the blood for Opisthorichis is not useful for patient management and no blood test to detect infection is 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 liver, bile duct, or gallbladder conditions.
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