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Hospital General de Segovia 40002 Segovia, Spain
A 47-year-old woman was referred to our institution after two episodes of right-sided abdominal pain. She had no history of fever, and no hepatomegaly was found at physical examination. Biochemical, cytologic, and blood data were all normal with the exception of an 11% eosinophil count. A biphasic helical CT scan revealed several hypodense lesions throughout the patient's liver. A subcapsular collection on the anterior segment of the right hepatic lobe, adjacent to a large hypodense hepatic nodule, was found (Fig. 3A). A cluster of small nodular lesions and a thin tortuous tract, both in a subcapsular location, raised suspicions of fascioliasis. A fine-needle aspiration was performed. The cytologic study of the specimen obtained from the largest lesion showed hemorrhagic necrosis and an inflammatory infiltrate of lymphocytes and abundant leukocytes, some of them eosinophils. Partial aspiration of the subcapsular collection revealed a cloudy yellowish white fluid with no signs of blood. Cytologic analysis revealed a cellular inflammatory infiltrate similar to that of the liver parenchymal lesion. Its culture yielded no pathogens. When directly questioned, the patient reported watercress ingestion. A serologic test was positive for Fasciola hepatica at a 1:2,560 dilution.
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In endemic areas, humans are frequently infected by F. hepatica. Two phases have been described for the clinical course of fascioliasis in humans. The first phase involves hepatic invasion by the parasite. During the second, or biliary, phase, the parasite may remain in the bile ducts for years [1, 2]. CT is a useful tool in diagnosing invasive hepatic fascioliasis. Alterations are found in most patients with the condition, and if the characteristic lesions are seen in a patient with peripheral blood eosinophilia, a diagnosis of F. hepatica may be suggested. Several cases of clinical complications or of atypical or confusing radiologic manifestations of this condition have been recently reported [3, 4]. The interesting thing about our patient is that the CT features exhibited, such as the large hepatic lesion, are not commonly seen and the presence of the subcapsular hemorrhagic collection, to our knowledge, has not been previously reported.
In invasive fascioliasis, the migration of the flukes through the hepatic parenchyma and into the bile duct is responsible for the pathologic alterations in the liver. Unlike the individuals lesions associated with pyogenic abscesses, hepatic microabscesses caused by F. hepatica do not coalesce to form a large abscess cavity. They do not tend to increase in size and generally evolve very slowly [2]. The differences between pyogenic abscess lesions and liver lesions seen in fascioliasis may be explained by the fact that the lesions in fascioliasis are caused by necrosis rather than by suppurative infection.
F. hepatica must penetrate Glisson's capsule to pass from the peritoneum to the liver parenchyma. Thus, whenever the liver is involved, the liver capsule and the subcapsular parenchyma are always affected. Two types of predominantly subcapsular hepatic lesions may be visualized on CT. The first type of lesion is seen as clusters of small hypodense nodular areas. The second, and more specific, type of lesion is seen as hypodense, tortuously branching tracts. On enhanced CT, the presence of a thickened and highly attenuated hepatic capsule also has been described as a characteristic CT feature of hepatic fascioliasis [1, 2]. A large hepatic subcapsular collection is an uncommon finding in patients with fascioliasis. A hemorrhagic subcapsular collection may be a complication during the invasive phase. On rare occasions, the bleeding may be life-threatening because of its severity or recurrence. The association of a subcapsular hematoma of the liver with eosinophilia suggests either polyarteritis nodosa or invasive hepatic fascioliasis [3]. To our knowledge, a subcapsular collection caused by an abscess in hepatic fascioliasis has not been previously reported. Usually, a patient with an acute subcapsular hematoma presents with abrupt pain, and the finding of high attenuation on unenhanced CT scans leads to the diagnosis. However, the CT appearance of a nonacute hematoma is similar to an inflammatory collection: both show hypodense subcapsular collections. The absence of anemia and a thickened and highly attenuated hepatic capsule around the subcapsular collection can confirm the inflammatory nature of the collection (Figs. 3A and 3B). If any doubt persists, the findings of a fineneedle aspiration can lead to the diagnosis.
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  A. Kabaalioglu, K. Ceken, E. Alimoglu, R. Saba, M. Cubuk, G. Arslan, and A. Apaydin Hepatobiliary Fascioliasis: Sonographic and CT Findings in 87 Patients During the Initial Phase and Long-Term Follow-Up Am. J. Roentgenol., October 1, 2007; 189(4): 824 - 828. [Abstract] [Full Text] [PDF]
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