The pathologic and clinical consequences of infection are directly related to the intensity and duration of infection. Most infected patients are considered to have an innocuous infection (less than 100 flukes), and rarely have symptoms. Five to ten percent of infected humans can have a very heavy parasite load. These patients can present with vague symptoms: right upper quadrant abdominal pain, nausea, vomiting, anorexia, malaise, and fevers. This occurs about 10 to 30 days after the ingestion of an infected fish. When these symptoms do occur, they usually are present for 2 to 4 weeks, with eggs becoming detectable in stool after 3 to 4 weeks. Peripheral eosinophilia may be present in some patients. Chronic symptoms are often observed in patients with a heavy burden of liver flukes. These symptoms are generally a result of chronic mechanical and physical injury of the bile ducts.

Chronic symptoms include vague abdominal pain, anorexia, increased bile acids, weight loss, dyspepsia, and diarrhea. Often, elevated alkaline phosphatase may be present. The heavy parasite burden can be particularly dangerous. High concentrations in the gallbladder can result in cholecystitis. Chronic obstruction of the bile ducts can result in ascending cholangitis, cholangiohepatitis, and cholangiocarcinoma. Dead flukes can also serve as a nidus for stone formation, forming pigment stones.[2][6]

The diagnosis is generally made from the presence of ova and parasites found in stool samples, duodenal aspirate or flukes found in biliary secretions are diagnostic. Standard diagnostic tests include a direct fecal smear, Kato-Katz method, which is a method of preparing stool samples where stool is pressed through the mesh, and the remaining sample is a piece of cellophane soaked in glycerol which clears the stool from the eggs. The gold standard diagnosis is through formalin ethyl-acetate concentration technique (FECT). Worms may also be found in endoscopic retrograde cholangiopancreatography (ERCP).[7][3]

Serological tests do exist to establish a diagnosis of C.sinensis. Today PCR techniques are being employed to make a rapid diagnosis within 24-48 hours.

Imaging including ultrasound, CT, MRI, and harmonic imaging are also used to determine the location, progression, and extent of the infection.

The most effective treatment for clonorchiasis is praziquantel 75 mg/kg orally three times per day for 1 to 2 days. This regimen cures about 99% of infected patients. Close to one hundred percent of patients are cured with a second treatment if they were not completely cured with the first treatment. Patients with severe or advanced sequelae of this disease, such as ascending cholangitis, may require biliary drainage or surgery. Symptoms of cholecystitis may require cholecystectomy. Patients’ family members and close contacts should also be tested for infection because it is more than likely that they may have eaten the same contaminated food. Liver abscesses, although rare with this parasite, should be managed carefully. The abscess should not be percutaneously aspirated as there is a risk of spillage into the abdomen. Patients with liver abscesses may require segmentectomy of the liver.[8][9]

Praziquantel does have unpleasant side effects and thus in some cases other drugs like artesunate, mebendazole and tribendimidine are also used.

Researchers have been trying to develop a vaccine but so far they have only been tested in animals.

The differential diagnosis includes acute hepatitis, cholecystitis, choledocholithiasis, cholangiocarcinoma, primary sclerosing cholangitis, and other parasitic infections, including schistosomiasis, strongyloidiasis, and ascariasis.[1]

The prognosis for most patients is good if they remain compliant with the medications. Those who do require surgery have a slightly longer recovery period and may develop surgery-related complications.

The liver flukes reside within the biliary tree and cause obstruction, inflammatory irritation, and fibrosis, which, when present for an extended time, can eventually lead to cholangiocarcinoma. Cholangiocarcinoma is the most severe and lethal outcome of a burdensome C. Sinensis infection. This will usually present with vague symptoms such as right upper quadrant pain, nausea, vomiting, and obstructive jaundice. The mainstay of treatment for cholangiocarcinoma is surgical resection. The specific required procedure is dependent on the location of the lesion and is discussed more in-depth under the cholangiocarcinoma article.[3]

Prevention of C. sinensis infection is heavily based on patient education and proper food preparation. Endemic areas promote education with public awareness programs, health guide booklets, and educating school children. These educational programs are enforcing proper food preparation and avoidance of undercooked or raw fish. Removal of farm animals from nearby fish farms and recognition of symptoms is also essential. These areas must undergo cultural changes to begin the decline of infection rates of C. sinensis, including replanting family farms to move farm animals from water sources and decreasing the consumption of raw fish in their diet.[3]

While most C. Sinensis infections are asymptomatic with a parasite load of approximately 100, acute infections require a more detailed and rigorous management strategy with several medical teams on board. Patients with a heavy parasite load of approximately 20,000 are at a higher risk for chronic, long-term issues. Such risks include ascending cholangitis, cholangiocarcinoma, and hepatitis. Once it has become clear that a parasitic liver infection has developed, it is important that gastrointestinal (GI)/surgery, internal medicine, and infectious disease specialists have a clear line of communication to begin therapy as soon as possible. Specialty trained nurses in infection control and gastroenterology should be involved in providing patient and family education, monitoring patients, and providing status reports to the interprofessional team. Pharmacists evaluate the appropriateness of medications prescribed, assess for drug-drug interactions, and participate in education. It is also important to make an accurate diagnosis of which parasite is the culprit of the current disease as there are several types of different parasitic liver infections. Clear communication between all involved specialties is important to ensure that the patient and any close contacts are treated quickly and properly to avoid any severe consequences. [Level 5]