Clinical Presentation in Humans
Most of the pathologic manifestations of clonorchiasis result from the inflammation and intermittent obstruction of the biliary ducts caused by the adult flukes. In the acute phase of the disease, abdominal pain, nausea, diarrhea, and eosinophilia can be major symptoms. There may be elevation in levels of alkaline phosphatase, alanine aminotransferase, transaminase, and bilirubin levels.
Chlonorchiasis is often an asymptomatic infection, but patients with a severe infestation may develop cholangiohepatitis and liver failure. Clinical manifestations are usually apparent if the worm load increases to 500-1000 flukes. In long-standing infections, cholangitis, cholelithiasis, pancreatitis, and cholangiocarcinoma can develop, which can be fatal if treatment is left too late. Interestingly, the occurrence of biliary stones in conjunction with clonorchiasis is associated with an increased incidence of carrying Salmonella typhi.
Abdominal x-rays may also demonstrate intrahepatic calcification. Percutaneous transhepatic cholangiography and CT scanning will reaveal dilatation of the peripheral intrahepatic bile ducts, and in severe cases, occasional cholangiocarcinoma. Round filling defects up to several millimeters in diameter may be caused by the adult worms.
The parasite causes thickening of the lining of the bile duct and an inflammatory response in the surrounding liver tissue. In heavy infections, the bile duct epithelium can also be deeply eroded, and the parasite's eggs will enter the liver tissue; in such cases the eggs become surrounded by a fibrotic capsule or granuloma. Particularly heavy infections can also result in stenosis-- narrowing or blockage-- of the bile ducts. Since the parasites can live for years and the number of parasites tends to increase as a person ages, the damage to the liver and bile duct tends to accumulate over time and can result in death.
As with many trematodes, diagnosis of the infection depends on recovering and identifying the parasite's eggs in a stool sample. Characteristic sonographic findings include diffuse dilatation of small intrahepatic ducts with minimal or absent dilatation of the extrahepatic ductal system. Increase in echogenicity and thickening of the involved bile duct walls are also present.