Clonorchiasis is infection with the liver fluke Clonorchis sinensis. Infection is acquired by eating undercooked freshwater fish. Symptoms include fever, chills, epigastric pain, tender hepatomegaly, diarrhea, and mild jaundice. Diagnosis is by identifying eggs in the feces or duodenal contents. Treatment is with praziquantel or albendazole.
Clonorchis is endemic in the Far East, especially in Korea, Japan, Taiwan, and southern China, and infection occurs elsewhere among immigrants and people eating fish imported from endemic areas.
Adult C. sinensis worms live in the bile ducts. Eggs are passed in the stool and ingested by snails. Cercariae (free-swimming larvae) released from infected snails subsequently infect a variety of freshwater fish. Humans become infected by eating raw, dried, salted, or pickled fish containing encysted metacercariae (resting or maturing stage). Metacercariae are released in the duodenum, enter the common bile duct through the ampulla of Vater, and migrate to smaller intrahepatic ducts (or occasionally the gallbladder and pancreatic ducts), where they mature into adult worms in about 1 mo. The adults may live ≥ 20 yr and grow to about 10 to 25 mm by 3 to 5 mm.
Symptoms and Signs
Light infections are usually asymptomatic. Heavier infections can cause fever, chills, epigastric pain, tender hepatomegaly, mild jaundice, and eosinophilia. Later, diarrhea may occur. Chronic cholangitis in heavy infections may progress to atrophy of liver parenchyma, portal fibrosis, and cirrhosis. Jaundice may occur if a mass of flukes obstructs the biliary tree. Other complications include suppurative cholangitis, chronic pancreatitis, and, late in the course, cholangiocarcinoma.
Diagnosis is by finding eggs in the feces or duodenal contents. The eggs are difficult to distinguish from those of Metagonimus, Heterophyes, and Opisthorchis. Occasionally, the diagnosis is made by identifying adult flukes in surgical specimens or by doing percutaneous transhepatic cholangiography.
Other tests are nondiagnostic but may be abnormal; alkaline phosphatase, bilirubin, and eosinophil counts may be elevated. A plain abdominal x-ray occasionally shows intrahepatic calcification. Hepatic ultrasonography may show ductal irregularities and evidence of scarring.
Treatment is with praziquantel 25 mg/kg po tid for 2 days or albendazole 10 mg/kg po once/day for 7 days. Biliary obstruction may require surgery. Freshwater fish from endemic waters should be thoroughly cooked and not eaten raw, pickled, or wine-soaked.
Last full review/revision December 2009 by Richard D. Pearson, MD