Clonorchiasis

Clonorchiasis is a liver fluke infection caused by Clonorchis sinensis (Chinese liver fluke), acquired by eating raw or undercooked freshwater fish containing metacercariae.

• Endemic in China, Korea, Vietnam, and Russia; about 15 million infected worldwide.
• Flukes live in intrahepatic bile ducts for 20 to 30 years.
• Chronic infection is associated with cholangitis, biliary stones, recurrent pyogenic cholangitis, and cholangiocarcinoma (IARC Group 1 carcinogen).

• Most infections are asymptomatic or mild (fatigue, indigestion).
• Heavy burdens: right upper quadrant pain, fever, hepatomegaly, jaundice, cholangitis, cholecystitis, and pancreatitis.
• Chronic complications: biliary strictures, intrahepatic stones, liver abscess, cirrhosis, and cholangiocarcinoma.
• Eosinophilia is variable.

• Stool microscopy for small operculated eggs (28 to 35 by 12 to 19 micrometres) using concentration or Kato-Katz; also in duodenal aspirate or bile.
• Serology (ELISA) and PCR; useful when egg shedding is low.
• Ultrasound, CT, MRCP: diffuse dilatation of peripheral intrahepatic bile ducts, thickened walls, and flukes.
• Tumour markers (CA 19-9) and biopsy if cholangiocarcinoma suspected.
• Exclude opisthorchiasis, fascioliasis, primary sclerosing cholangitis, and choledocholithiasis.

• Praziquantel 25 mg/kg three times daily for 2 days, or 40 mg/kg as a single dose (cure rates 85 to 100%).
• Alternative: albendazole 10 mg/kg/day for 7 days.
• Antibiotics for cholangitis (ceftriaxone, metronidazole); biliary drainage via ERCP or percutaneous routes for obstruction; cholecystectomy for gallstones.
• Surveillance for cholangiocarcinoma with ultrasound in endemic or heavily infected individuals.
• Prevention: thoroughly cook or freeze freshwater fish, health education, and community mass praziquantel treatment.