Ultrasonographic findings of small lesion of hepatic alveolar echinococcosis

- Hepatic alveolar echinococcosis (AE) is rare, but it often appears as a mass that it is hard to be differentiated from other cancerous lesions only by US.
- In recent years, contrast enhanced ultrasound (CEUS) is used in characterization of focal liver lesions (FLLs), such as hepatic cell carcinoma.
- The enhancement patterns of several FLLs have been described and are well known. However, the US and CEUS features of small lesion of hepatic AE has not been investigated or reported in the English-language literature.
- CEUS is the application of contrast agent to traditional US. CEUS can be used to image blood perfusion in organs. US and CEUS can be used to diagnose the small lesion of hepatic AE.

ObjectiveTo investigate the features of small lesions of hepatic alveolar echinococcsis paragonimiasis (AE) on conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS) imaging.MethodsThis 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 (≤3 cm). 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 2.4 mL of a sulfur-hexafluoride-filled microbubble contrast agent (SonoVue) was administered. The features of the lesions by US and CEUS were retrospectively reviewed.ResultsIn total, all lesions were detected by US and CEUS. The mean size of the lesions was 1.8 ± 0.7 cm (range: 1.0-3.0 cm). 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.ConclusionHyperechogenicity, 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.