Radiological Imaging Features of Fasciola hepatica Infection – A Pictorial Review

Abstract

Fascioliasis refers to a zoonosis caused by Fasciola hepatica, a trematode infecting herbivores, but also occurs in humans who ingest the metacercaria found in fresh water plants. Infection in humans is common in developing countries and is also not uncommon in Europe. Diagnosis of this infection is difficult, as the history and symptoms are nonspecific and stool analysis for eggs is negative until the disease is in an advanced state by when the parasite has reached the biliary system. The clinical course consists of two phases; first a hepatic parenchymal phase in which immature larvae invade the liver parenchyma, followed by a ductal phase characterized by the excretion of larvae into the bile ducts. Parenchymal Phase: Ultrasonography (US) findings are nonspecific in this early phase. Computerized tomography (CT) may demonstrate subcapsular low attenuation regions in the liver. Magnetic Resonance imaging (MRI) can also be utilized to establish liver parenchymal involvement, and is better than CT in characterizing hemorrhagic lesions, as well as identifying more lesions relative to CT. Ductal Phase: US examination is most useful at this stage, with its ability to demonstrate the live movement of the worms within the dilated ducts. A CT demonstrates dilated central biliary ducts with periportal tracking, whereas, mild ductal dilatation is poorly appreciated under MRI. Therefore, familiarity with the multimodality imaging features of fascioliasis, in combination with an available confirmatory enzyme-linked immunoassay, would be most helpful for early diagnosis.

Human liver flukes

“…Enlarged porta hepatis nodes are visible in 51% on US or CT (93) . Biliary abnormalities are present in 45% of cases and may include visible parasites in the gallbladder or bile ducts, or biliary duct dilatation, thickening, oedema or abnormal enhancement (93,95) . After eight weeks ductal ectasia may be seen with bile duct thickening, dilatation and tortuosity occurring after 12 weeks (95) .…”

“…Biliary abnormalities are present in 45% of cases and may include visible parasites in the gallbladder or bile ducts, or biliary duct dilatation, thickening, oedema or abnormal enhancement (93,95) . After eight weeks ductal ectasia may be seen with bile duct thickening, dilatation and tortuosity occurring after 12 weeks (95) . Other findings include mild splenomegaly, ectopic inflammation in the abdominal wall or bowel (93) .…”

Investigation of Fasciola hepatica Seropositivity in Forensic Autopsies in the Çukurova Region

“…The highest prevalence was found in Bolivia, where stool examination revealed a prevalence of 72%, and serologic tests were positive in 100%. 8,9 Lopez et al investigated the prevalence of Fasciolosis in school age children in Peru and they reported that 10.3% had positive stool microscopy. 10 There have been several epidemiologic studies on Fasciolosis in Turkey.…”

Fasciola hepatica as an uncommon cause of cholangitis

“…Biliary parasitosis may lead to a series of complications such as obstructive jaundice, pyogenic cholangitis, acute pancreatitis, intrahepatic stones, liver abscesses, acute or chronic cholecystitis, and even cholangiocarcinoma and hepatocellular carcinoma [1 -3]. Imaging techniques such as ultrasound, computed tomography, and MRCP are usually non-specific [4]. Only the serology and identification of ova in the stool or duodenal aspirates are specific, but not routinely done in clinical practice [1].…”