Last revised by Joshua Yap on 29 Jun 2022

Clonorchiasis is a trematodiasis caused by chronic infestation by Clonorchis sinensis and can lead to recurrent pyogenic cholangitis, biliary strictures and cholangiocarcinoma

Infection with Clonorchis sinensis occurs in endemic areas, mainly east China. Over 85 million people are estimated to be infected with the vast majority (85%) in China. There is a male predominance (M:F = 2:1) 3

Signs and symptoms are usually mild and nonspecific, but heavy infestation results in obstructive jaundice. Additionally, patients may present with one of the complications of clonorchiasis, including:

Infection occurs after ingestion of infected raw flesh of freshwater fish.

The adult flukes reside in the medium-sized and small intrahepatic bile ducts and, occasionally, in the extrahepatic bile ducts, gallbladder, and pancreatic duct.

They may cause a mechanical obstruction, inflammatory reaction, adenomatous hyperplasia, and periductal fibrosis.

Whether imaged directly (percutaneous transhepatic cholangiography (PTC) or ERCP) or indirectly (CT IVC or MRCP) the appearances of the biliary tree are similar. 

Cholangiograms show many elongated filling defects from a few millimeters to 10 mm in length (representing the flukes) and intrahepatic duct dilatation, which is more pronounced in the peripheral regions. These are only readily seen on direct cholangiography, as the resolution of CT and MRI is usually insufficient. 

Diffuse, uniform dilatation of the small intrahepatic bile ducts with no or minimal dilatation of the large bile ducts and no focal obstructing lesions is characteristic. 

Flukes live in the peripheral small and medium-sized bile ducts, resulting in longstanding incomplete obstruction. The flukes themselves are however not usually visible as they are very thin and beyond the spatial resolution of these modalities. 

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