Hepatobiliary fasciolasis.

Fasciolasis is a rare zoonotic disease, caused by the sheep liver fluke, Fasciola hepatica. It affects primarily bovine and ovine cattle, and by chance, humans.

Infection results from ingesting uncooked watercress and other fresh aquatic vegetation in many countries worldwide, specially in sheep and cattle-raising areas. Other freshwater plants may also transmit infection, including water lettuce, mint, alfalfa, and parsley. (1)

Ingested infective form metacercaria excyst in the intestine, penetrate the bowel wall, enter the peritoneum and then pass through the liver capsule to enter the biliary tree (2) . Human fascioliasis has two phases. The hepatic phase of the disease begins one to three months after ingestion of metacercariae, with penetration and migration through the liver parenchyma toward the biliary ducts. The biliary phase begins  when the fluke is in the bile ducts. Itincludes syntoms like intermittent fever, abdominal pain, weight loss, headache and itch or urticaria. There may be tender hepatomegaly and normal or minimally elevation of liver enzymes. (4)

A long list of diseases must be included in the differential diagnosis: viral hepatitis, liver abscess, cholecystitis, cholelithiasis, biliary sludge, Caroli’s disease, brucellosis, hepatobiliary-pancreatic malignancies, ruptured hydatid cyst, ascariasis, clonorchiasis, and other parasites (3)

 For the diagnosis of F. hepatica, there are several methods which can be useful at different stages of the disease: stool culture, serology, images techniques or biopsy.(5)

The blood cells count reveals mild to moderate anemia, mild leukocytosis and often hypereosinophilia, the latter being the most frequent laboratory abnormality found. However, it has been described that 15-20% of patients showed no eosinophilia.(6)

Serology is helpful in the diagnosis of fasciolasis, especially during acute infection because symptoms develop 1 to 2 months before eggs are detectable in the stool. The method most widely use is ELISA The essay detects antibodies. Sensitivities of more than 90 % are reported, but the specificity may be less owing to cross-reactivity with other helminths. (2)

The US, CT, and MRI findings of fascioliasis have been described and classified . The most common imaging findings of fascioliasis are multiple small nodular and branching linear lesions, frequently in the subcapsular areas of the liver parenchyma— that appear hypoechoic on US, hypodense on CT, and T1 hypointense and T2 hyperintense on MRI. (3)

CT scan shows multiple low-attenuated nodular or tortuous masses with or without rim enhancement after administration of intravenous contrast (7). Typically, the maximum diameter of the lesions are no larger than 2–3 cm (5).

Branching pattern and subcapsular locations of the lesions are the most commonly seen abnormalities on the CT scan.

Enhanced liver capsular thickening  and subcapsular hemorrhage may also be present, but should not be considered a sensitive and specific CT finding.(7)

CT scan is negative or inespecific showing dilated bile ducts. Common bile ducts wall thickening is better observed by ultrasonography (US) than CT scan.

Another feature in patients with fascioliasis is the slow evolution of the lesions, which can be seen after 6–12 months (5).

CT scan is useful for confirmation of diagnosis evolution and follow-up of medical therapy.(7)

Percutaneous needle liver biopsy reveals non specific changes. Charcot-leyden crystals and multiple calcification foci and rarely demonstrates fasciola eggs or fasciola hepatica organisms.  (2)

Actually Triclabendazole is the first-line treatment of F. Hepatica. 80% of patients present cure with a single dose, the rest can respond to a second dose. Treatment should be repeated if radiographic findings or eosinophilia fail to resolve or the titers of the serologic tests do not decrease.  Alternative therapy is with bithionol, which can cause effects frequently. The chronic infection is more difficult to treat compared to the acute disease.  (2)