Disseminated alveolar hydatid disease resembling a metastatic malignancy: a diagnostic challenge-a report of two cases

The spectrum of multimodality imaging findings in hepatic alveolar echinococcosis and the potential role of diffusion-weighted imaging in its characterisation

Purpose

To study the spectrum of imaging findings in hepatic alveolar echinococcosis (HAE) and to evaluate the potential role of diffusion-weighted imaging (DWI) in its characterisation.

Material and methods

Two radiologists with more than seven years of experience retrospectively studied ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) findings in 23 histopathologically proven cases of HAE with emphasis on the appearance and extent of disease. DWI characteristics of lesions were noted, and their apparent diffusion values (ADC) were calculated.

Results

Ultrasonography features of HAE included heterogeneous, hyperechoic hepatic mass with or without calcification (n = 20), or heterogeneous mass with solid-cystic appearance (n = 2). CT revealed heterogeneous density infiltrative hepatic mass with no contrast enhancement in 19 patients or thick-walled cystic mass (n = 4). Following Kodama classification one type 1, six type 2, two type 3, eight type 4, and two type 5 lesions were identified on T2-weighted MRI. No enhancement was seen on post-contrast T1-weighted images. Mean ADC values were 1.74 ± 0.48 × 10^-3 mm²/s (range: 1.39 × 10^-3 mm²/s to 2.3 × 10^-3 mm²/s).

Conclusions

HAE by virtue of its infiltrative growth pattern with a tendency to involve biliary, vascular, and extra hepatic structures can be easily misdiagnosed as malignant hepatic neoplasm. Knowledge of varied imaging appearances of HAE is essential to suspect the condition and to make an appropriate diagnosis. Diffusion-weighted imaging is a useful adjunct with relatively high diffusivity (high ADC values) suggesting diagnosis of alveolar hydatid.

Disseminated cerebral hydatid disease (multiple intracranial echinococcosis)

Intracranial echinococcosis is relatively uncommon and usually occurs in the context of echinococcal lesions elsewhere in the body, mostly liver and lung. Multiple intracranial lesions can result from rupture of an initial single intracranial cyst (in cystic echinococcosis) or from dissemination of systemic disease of the lung, liver or heart (cystic and alveolar echinococcosis). The two main subtypes, cystic and alveolar echinococcosis, present differently and have distinct imaging features in the brain. We discuss the presentation, imaging findings and clinical course of three cases (two cystic and one alveolar) of intracranial echinococcal disease in adults.

A report on three patients with Echinococcus multilocularis: Lessons learned

Echinococcus multilocularis (EM) is the most virulent species of the genus Echinococcus. It causes a highly lethal helminthic disease in humans. The disease may present as hepatic mass mimicking a malignant neoplasm. Due to the vascular and neural invasion, protean clinical manifestations including Budd-Chiari syndrome (BCS) may be the clinical presentation of this condition. We herein report three cases of Echinococcus multilocularis; the first case presenting as multiple hepatic space-occupying lesions, second as liver mass infiltrating the nerve bundles, and the third as a hepatic mass infiltrating the large vessels including inferior vena cava and right hepatic vein presenting as BCS. EM is a parasite with capabilities of mass-forming effect, neural and vascular invasion. Though cases of BCS have been described, most of these are due to secondary compression and rarely by direct parasitic invasion.

Ultrasonographic findings of small lesion of hepatic alveolar echinococcosis

OBJECTIVE

To investigate the features of small lesions of hepatic alveolar echinococcsis paragonimiasis (AE) on conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS) imaging.

METHODS

This retrospective study was approved by the Institutional Review Board, and the requirement for informed consent was waived. US and CEUS features of seventeen lesions histopathologically proven hepatic AE were retrospectively reviewed. Nine patients with seventeen hepatic AE lesions who were admitted to our hospital between January 2008 and June 2015 were enrolled. All hepatic AE lesions were small (≤3cm). The US and CEUS examinations were performed with a Philips IU22 scanner with a 1-5-MHz convex transducer. After US was completed, the CEUS study was performed. Pulse-inversion harmonic imaging was used for CEUS. A bolus injection of 2.4mL of a sulfur-hexafluoride-filled microbubble contrast agent (SonoVue) was administered. The features of the lesions by US and CEUS were retrospectively reviewed.

RESULTS

In total, all lesions were detected by US and CEUS. The mean size of the lesions was 1.8±0.7cm (range: 1.0-3.0cm). Five patients (55.6%, 5/9) had a lesion in the right hepatic lobe; two (22.2%, 2/9) had two lesions in the left hepatic lobe; and two patients (22.2%, 2/9) had four lesions in the right lobe. Seven lesions (41.2%, 7/17) were hypoechoic nodules and ten (58.8%, 10/17) were hyperechoic nodules. Nine lesions (52.3%, 9/17) were of mixed echogenicity type. Ten lesions (58.8%, 10/17) had a regular shape. Nine lesions (52.3%, 9/27) had a sharp margin and six (35.3%, 6/17) had indistinct margins. Four lesions (57.1%, 4/7) with hypoechoic nodule had small dotted calcifications, none was found in hyperechoic nodule. Seven nodules (41.2%, 7/17) showed short striated blood-flow signals surrounding the margin, on color Doppler flow imaging. By CEUS, All the lesions were hypoechoic with mixed content (). 12 lesions (70.1%, 12/17) were rim enhanced with irregular piece-like nonenhanced internal areas and showed nonhomogeneous hypo-enhancement during the arterial phase, with mixed echogenicity. The main pathological findings included: (1) (1) coagulative or liquefactive necrosis within the lesion with sporadic distribution of wizened alveolar hydatid cysts; and (2) hyperplasia of granulomatous and fibrous tissue around the lesion.

CONCLUSION

Hyperechogenicity, mixed echogenicity type, dotted calcification with hypoechogenicity, sharp margin, rim enhancement and piece-like nonenhanced areas could be seen as the main ultrasonographic features of small lesion of hepatic alveolar echinococcosis.

Multimodality imaging in diagnosis and management of alveolar echinococcosis: an update

Alveolar echinococcosis is a parasitic disease limited to the northern hemisphere. The disease occurs primarily in the liver and shows a profile mimicking slow-growing malignant tumors. Echinococcus multilocularis infection is fatal if left untreated. It can cause several complications by infiltrating the vascular structures, biliary tracts, and the hilum of the liver. As it can invade the adjacent organs or can spread to distant organs, alveolar echinococcosis can easily be confused with malignancies. We provide a brief review of epidemiologic and pathophysiologic profile of alveolar echinococcosis and clinical features of the disease. This article focuses primarily on the imaging features of alveolar echinococcosis on ultrasonogra-phy, computed tomography, magnetic resonance imaging, diffusion-weighted imaging and positron emission tomography-computed tomography. We also reviewed the role of radiology in diagnosis, management, and follow-up of the disease.