Fasciola Hepatica: An unusual liver lesion

A 41-year-old British male, with no travel history, presented to our hospital with a 3 week history of back pain radiating to his abdomen with associated weight loss, loose stools and macroscopic haematuria. On initial presentation, his inflammatory markers were within normal limits and eosinophil count at this time was also normal.

Initial MRI abdomen showed a 38mm serpiginous focal hepatic lesion. This remained hypointense to the parenchyma on T2W sequence, with high-intensity walls. The walls showed enhancement on post-contrast sequence, while no internal enhancement was seen.

A 6 month follow-up contrast enhanced ultrasound scan (CEUS) was performed. On B-mode the lesion remained hypoechoic with some internal bright foci. On post-contrast sequence, the internal foci did not show any enhancement. The walls of the lesion also did not show any enhancement.

A MRI liver with contrast was performed a week after the CEUS. On T2W sequence, the lesion demonstrated low signal, as was seen in the initial MRI scan performed 6 months earlier. However, unlike the previous scan, the walls of the lesion did not show high signal. On post-contrast sequence, the wall of the lesion did not show any enhancement. Furthermore, non-enhancing internal foci were also demonstrated, similarly to the CEUS.

Overall, the changes seen in 6 month follow-up scans were respectively: loss of enhancement of walls and development of non-enhancing internal debri.

This lesion was initially reported as an indeterminate focal hepatic lesion, raising the possibility of an atypical tumour. The case was referred to the hepatobiliary MDT, where the diagnosis of Fasciola Hepatica was made, considering the serpiginous worm-like configuration.

On the follow-up CEUS and MRI scan, non-enhancing internal debri and lack of wall enhancement possibly suggests that the worm is now dead.

Fascioliaisis is a tropical disease that affects millions word-wide and refers to a zoonosis caused by Fasciola hepatica and Fasciola gigantica, a trematode which can infect humans who ingest contaminated water or fresh water plants (1). Human infections are predominantly in developing countries including Africa, South America, North and South Asia including China and Korea (2).

Infection is uncommon in Europe and therefore clinicians may be unfamiliar with the presentation, possibly contributing to delays in diagnosis and the potential for complications including biliary colic, cholecystitis and acute cholangitis with abscess formation (1).

Approximately 50% of human infections are asymptomatic (3) and diagnosis is difficult due to the nonspecific nature of symptoms with stool analysis only being accurate when the disease is advanced (1). In acute fascioliasis symptoms may include intermittent fever, abdominal pain and malaise. Eosinophilia and urticaria are common features.

Radiological findings often have characteristic features and are therefore useful in aiding diagnosis and it is important to distinguish fascioliasis from alternative focal liver lesions via imaging (1).

There are two key stages seen in imaging: the parenchymal phase and the ductal phase.

During the parenchymal phase, CT may demonstrate subcapsular low attenuation lesions in the liver and MRI may be more specific in identifying lesions especially haemorrhagic lesions. Liver lesions are hyperintense on T2 and hypointense on T1 with peripheral enhancement following  the administration of contrast. Findings on ultrasound during this early phase are non-specific. (1).

During the ductal phase, ultrasound is most useful due to the ability to emphasise the live movement of worms within the ducts. During this phase liver lesions may regress, ultrasound may demonstrate ductal ectasia with duct wall thickening, ductal dilatation adjacent to portal areas and biliary dilatation (1). CT may highlight dilated biliary ducts with periportal tracking. However, on MRI mild duct dilatation is poorly appreciated. Therefore multiple modes of imaging are helpful in the accurate diagnosis of Fascioliasis and in continuity of care following treatment.

Take-Home Messages

Fascioliasis is rarely seen in the UK and presents with a non-specific clinical picture. These lesions can easily be mistaken for other focal hepatic lesions. Therefore, the imaging features of Hepatica Fasciola should be remembered in order to establish an accurate diagnosis. 

Written informed patient consent for publication has been obtained.