Hepatic alveolar echinococcosis. A case report

Two Cases of Disseminated Alveolar Echinococcosis: The Diagnosis, Management, and Differential Considerations for Liver Lesions

Alveolar echinococcosis (AE), caused by Echinococcus multilocularis, is an aggressive and potentially critical infestation that primarily affects the liver and can metastasize to any part of the body. We herein report two cases of echinococcosis, which could be differentiated from malignancy on imaging studies, with infections of the liver and mediastinal lymph nodes, and also associated with systemic disseminated lesions. AE is a very invasive infectious disease, and in order to detect such lesions at an early stage when they are still resectable, it is necessary to understand the characteristic imaging findings and determine the patient's current medical history.

A review of the diagnosis and management of liver hydatid cyst

Hydatidosis is a zoonosis caused by Echinococcus in the larval stage. Humans are accidental intermediary hosts where cystic lesions develop, primarily in the liver and lungs. It is usually asymptomatic, hence it is usually incidentally identified. Symptoms result from cyst expansion and/or host inflammatory reaction. Hepatomegaly is the most common sign. Hydatidosis induces no specific changes in lab tests, but immunodiagnostics are available that may complement its study, with antibody detection being the method of choice. While ultrasound is the main diagnostic technique, tomography offers more accurate information regarding characteristics and anatomical relations. A number of therapy options are presently available. Treatment with albendazole, whether combined or not with praziquantel, is useful for smaller, uncomplicated cysts (< 5 cm). Only 30 % of cysts disappear with medical treatment alone. Surgery is indicated for bigger liver cysts (> 10 cm), at risk for rupture and/or complicated; the laparoscopic approach is scarcely widespread. The radical technique (total cystopericystectomy) is preferable because o its lower risk for postoperative abdominal infection, biliary fistula, and overall morbidity. Conservative techniques are appropriate in endemic areas where surgery is performed by nonspecialist surgeons. PAIR (puncture-aspiration-injection-reaspiration) is an innovative technique representing an alternative to surgery. It is indicated for inoperable cases and/or patients who reject surgery, for recurrence after surgery, and for lack of response to medical treatment. Active surveillance without treatment may be indicated for quiescent or inactive, uncomplicated liver cysts.

Diagnostic imaging and interventional procedures in a growing problem: Hepatic alveolar echinococcosis

Alveolar echinococcosis (AE) of the liver is caused by the metacestode of the fox tapeworm Echinococcus multilocularis (E. multilocularis), which is endemic in many parts of the world. AE is a very aggressive and potentially fatal infestation which always affects the liver primarily and metastasizes to any part of the body. Without timely diagnosis and therapy, the prognosis is dismal, with death the eventual outcome in most cases. Diagnosis is usually based on findings at radiological imaging and in serological analyses. The alveolar cysts grow by exogenous proliferation and behave like a malignant neoplasm. Since AE lesions can occur almost anywhere in the body, familiarity with the spectrum of cross-sectional imaging appearances is advantageous. Therefore, AE lesions can cause physicians to generate a long list of differential diagnoses, including malignant tumors. Disseminated parasitic lesions in unusual locations with atypical imaging appearances may make it difficult to narrow the differential diagnosis. For diagnosis, ultrasonography (US) remains the first line examination. For a more accurate disease evaluation, aiming to guide the surgical strategy, computed tomography (CT), magnetic resonance imaging (MRI), including magnetic resonance cholangiography (MRC) imaging, are of importance, providing useful complementary information. However, making the correct diagnosis is possible if imaging findings are correlated with appropriate clinical findings. We present an overview of the radiological patterns produced by E. multilocularis lesions as seen on US, CT and MRI and discuss the interventional procedures in hepatic AE lesions.

Echinococcosis of the liver

Echinococcosis, also known as hydatid disease, is an infection of larval stage animal tapeworm, Echinococcus. The larvae reside in the liver and lungs, producing multiloculated fluid-filled cysts. Imaging findings of Echinococcosis caused by E. granulosus are single, unilocular cyst or multiseptated cysts, showing "wheel-like", "rosette-like" or "honeycomb-like" appearances. There may be "snow-flakes" sign, reflecting free floating protoscoleces (hydatid-sand) within the cyst cavity. Degenerating cysts show wavy or serpentine bands or floating membranes representing detached or ruptured membranes. Degenerated cysts show heterogeneous, solid-looking pseudotumor that may show "ball of wool sign". Dead cysts show calcified cyst wall. Echinococcosis caused by E. multilocularis produces multilocular alveolar cysts with exogeneous proliferation, progressively invading the liver parenchyma and other tissues of the body. Imaging findings are ill-defined infiltrating lesions of the liver parenchyma, consisting of multiple small clustered cystic and solid components. On sonography, lesions are heterogeneous with indistinct margins, showing "hailstorm appearance" or "vesicular or alveolar appearance". CT and MR imaging displays multiple, irregular, ill-defined lesions. Multiple small round cysts with solid components are frequent. Large lesions show "geographical map" appearance. Calcifications are very frequent, appearing as peripheral calcification or punctuate scattered calcific foci. Invasion into the bile ducts, portal vein or hepatic vein may occur. Direct spread of infected tissue may result in cysts in the peritoneal cavity, kidneys, adrenal gland or bones.

Complete resolution of an alveolar echinococcosis liver lesion following percutaneous treatment

Herein we present a 63-year-old male patient with a solid hepatic alveolar echinococcosis diagnosed by surgical biopsy. His liver lesion, which was infected, was drained by percutaneous catheterization. The lesion surprisingly disappeared completely after the treatment. The patient was followed-up without any symptoms for 20 months after the drainage. As alveolar echinococcosis of the liver behaves like a slow-growing liver cancer, the disappearance of our patient's lesion was a very unusual and rare outcome, which, to the best of our knowledge, has never been published in the literature.

The ability of67ga scintigraphy to detect the lesions ofEchinococcus multilocularis infection: Preliminary results

AIM

To assess the ability of 67Ga scintigraphy to detect the lesions of Echinococcus multilocularis (EM) infection.

MATERIALS AND METHODS

An animal model of EM infection was developed. The infected tissues taken from stock infection were placed into the abdominal cavity of uninfected animals operatively. The success of implantation was controlled 20-25 days after implantation. Five infected and 2 healthy animals were studied. All of the animals were examined by ultrasound before the scintigraphic evaluation. After the injection of 7.4 MBq (200 microCi) 67Ga citrate intravenously, static images from the whole anterior thorax and abdomen were obtained at 24, 48 and 72 hours. Visual and semiquantitative analyses were performed. In semiquantitative analysis, an irregular region of interest was drawn over the thorax as the background, excluding the heart and a second region of interest was drawn over the abdomen, excluding the liver and spleen. Abdomen/ background ratios were calculated using the mean counts.

RESULTS

In the visual evaluation, it was noticed that there was considerably increased 67Ga uptake in the abdomens of the infected animals. In infected animals, mean abdomen/background ratios at 48 and 72 hours (3.76 +/- 1.04, 4.13 +/- 0.72, respectively) were increased compared with mean abdomen/background ratios at 24 hours (2.94 +/- 0.77). These increases in abdomen/background ratios were statistically significant at 72 hours (p = 0.04). Between the infected animals and control group, mean abdomen/background ratios were compared, and statistically significant differences were found in the images obtained at 48 and 72 hours.

CONCLUSION

Imaging at 72 hours seems to be more suitable imaging time for the diagnosis of alveolar echinococcosis. 67Ga scintigraphy may successfully demonstrate the lesions of EM infection localized intraperitoneally. The method of 67Ga scintigraphy is useful because it is simple, non-invasive and relatively safe.