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Laboratory Diagnosis

The possibility of clonorchiasis should be kept in mind in evaluating obscure liver disease, sometimes associated with diarrhea and jaundice, in patients from endemic areas of the Far East. The diagnosis is established by detection of the characteristic eggs in feces (formalin-ether sedimentation is the preferred method of stool examination), or in bile or fluid obtained by duodenal intubation. Since several species of flukes are parasitic in humans and all produce similar operculated eggs, diagnosis of the precise infection depends on identifying adult worms recovered at surgery, at autopsy, or in stool following antihelminthic therapy.

There may be an associated leukocytosis of over 30,000 and a high eosinophilia (sometimes over 40%). Intradermal skin tests and a variety of serological studies, including complement fixation tests using an antigen made from a saline extract of Clonorchis, an indirect hemagglutination test, electrophoresis, ELISA and immunosorbent assay have all been employed with varying degrees of success in establishing a diagnosis. Liver biopsy may also be helpful in some patients.

Clinical Characteristics

It is important to remember that, even in highly endemic areas, the majority of persons infected with C. sinensis harbor few flukes and are virtually asymptomatic. In symptomatic patients, three stages in the development of the disease are recognized, depending on the severity of the infection. Symptoms develop 1-3 weeks after ingestion of metacercariae.

1. Early manifestations include fever, indigestion, epigastric and right upper quadrant pain, leukocytosis and eosinophilia.

2. In the second stage, there may be diarrhea, anorexia, prolonged low-grade fever, liver tenderness, and progressive hepatomegaly with episodes of jaundice.

3. Patients with advanced disease may show cirrhosis (Fig. 21.10), ascites, anasarca, cachexia resembling that of "sheep rot," hyperbilirubinemia and, at times, jaundice.

Patients rarely succumb from clonorchiasis alone and the prognosis is good in a light to moderate infection. However, death can occur in severe chronic infections where the flukes have caused serious hepatobiliary damage and impaired liver function or where cholangiocarcinoma has developed.

Praziquantel is the drug of choice today (2,000) in the treatment of both clonorchiasis and opisthorchiasis. The standard dose is 25mg/kg given orally three times in a single day, which probably cures all patients with opisthorchiasis. When the total daily dose 75 mg/kg is divided into 3 doses over a 2 day period, the cure rates for clonorchiasis are reported as 98-100%. A mass treatment program undertaken in South Korea resulted in a reduction in the prevalence of clonorchiasis from 13.3% in 1984 to 0.9% in 1990. The biliary tract abnormalities have been shown to regress following praziquantel therapy.

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