Focal Liver Lesions (FLL) with Acoustic Radiation Force Impulse (ARFI) Elastometry

Characterization of focal liver lesions (FLL) with acoustic radiation force impulse (ARFI) elastometry, Heide R, Strobel D, Bernatik T, Goertz RS.
Ultraschall Med. 2010 Aug;31(4):405-9. Epub 2010 Jul 22.

Abstract

PURPOSE:

The technology of acoustic radiation force impulse (ARFI) represents an innovative method for the quantification of tissue elasticity. The aim of this prospective pilot study was to evaluate the role of ARFI elastometry of focal liver lesions (FLL) and the surrounding liver parenchyma.

MATERIALS AND METHODS:

All patients with unclear FLL in B-mode ultrasound were assigned to ARFI elastometry (m/sec). Measurement sites were located within the FLL, in the peritumoral tissue and in hepatic segment VIII (intercostal approach). Histology and CEUS served as the reference for the characterization of the lesions.

RESULTS:

A total of 81 patients were enrolled, of whom 62 patients (39 females, 23 males; mean age 54 years) had FLL measurable by means of ARFI. The lesions were: 38 benign (61 %) and 24 malignant FLL (39 %). The ARFI elastometric values of the FLL differed significantly from those of the liver parenchyma (p < 0.001). Elastometry of benign lesions and of malignant tumors showed statistically comparable results (p = 0.28). The lowest ARFI values were observed in focal fatty sparing and the highest in HCC. Only focal fatty sparing and HCC showed negative differences between FLL and peritumoral tissue or liver parenchyma. In 23 % of the hepatic lesions, no reliable quantitative ARFI results were obtainable due to false, inconsistent or technically failed measurements.

CONCLUSION:

FLL vary in ARFI elastometry. However, high ARFI values occur in benign as well as in malignant lesions and do not permit differentiation between them.
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VON MEYENBURG COMPLEX  TRONG GAN và TẠO HÌNH ARFI

JASMINE THANH XUÂN, PHẠM THỊ THANH XUÂN, LÊ THANH LIÊM, NGUYỄN THIỆN HÙNG, Trung tâm Y khoa MEDIC Hoà Hảo, Thành phố Hồ Chí Minh, Việt nam.


Chúng tôi trình bày một trường hợp phức hợp von Meyenburg hay hamartoma đường mật ở một phụ nữ 29 tuổi không có triệu chứng lâm sàng, được phát hiện tình cờ khi khám siêu âm check-up. Đây là ca Von Meyenburg complex đầu tiên được khảo sát bằng siêu âm đàn hồi ARFI với máy ACUSON S2000 tại trung tâm Y khoa MEDIC Hoà Hảo, Việt nam.

Hình 1: Trên nền gan biến dạng như viêm gan mạn, có nhiều nốt echo dày và kém rải rác, có comet tail artifact và không có bóng lưng. Không tìm thấy nang gan nào trong cả 2 thuỳ. Kỹ thuật eSie Touch, với đầu dò curve 4C1 cho thấy nhu mô gan không đồng dạng, mã màu đỏ và vàng cam (cứng) với quality factor (QF)=65.

Hình 2-3: Các nốt echo dày, là các chỗ giãn thành nang chứa chất keo của đường mật, có tốc độ sóng biến dạng trung bình (SWV)= 1,22+/-0,03 m/s của dời chỗ ARFI ở độ sâu trung bình 4cm trong khi nền gan  có SWV=0,95+/-0,06 m/s với virtual tissue quantification (VTQ).

Hình 4: Với đầu dò linear 9L4, kỹ thuật virtual tissue imaging (VTI) trình bày các nốt echo dày ở hình B-mode, có darker color hơn mô gan, kích thước =1,9-2,1-2,2mm. Bờ gan không phẳng mịn như hình B-mode mà dày không đều [từ 1,2-1,8-1,9mm] và sậm màu hơn mô gan.

Hình 5: Dùng tiện ích vẽ tự động và tính area ratio của máy, mỗi nốt ( chỗ giãn đường mật) có diện tích lớn hơn hình B-mode= 0,22-0,42mm2 có thể do desmoplastic reaction xung quanh tổn thương.

Theo chúng tôi biết, chưa có báo cáo siêu âm đàn hồi nào về hamartoma đường mật (von Meyenburg complex).

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Sonographic Features of Biliary Hamartomas With Histopathologic Correlation, B. Keegan Markhardt, Deborah J. Rubens, Jiaoti Huang, Vikram S. Dogra, J Ultrasound Med 2006; 25:1631–1633.

Biliary hamartomas (BH) are uncommon benign biliary malformations composed of disorganized bile ducts and fibrocollagenous stroma. Biliary hamartomas are associated with autosomal dominant polycystic kidney disease (ADPKD), polycystic liver disease (PLD), Caroli disease, and congenital hepatic fibrosis. The major clinical importance of BH is that they may be misdiagnosed as multiple liver metastases, microabscesses, lymphoma, leukemia, Candida albicans, or extrapulmonary Pneumocystis carinii infection at initial imaging. In patients with ADPKD, these may be mistaken for small cysts, cirrhotic changes, or one of these more ominous diseases. The following report illustrates the distinguishing sonographic features of BH in a patient with ADPKD with histopathologic correlation.

Discussion

Biliary hamartomas were first described by von Meyenburg in 1918 and are referred to as von Meyenburg complexes. Biliary hamartomas are uncommon benign biliary malformations composed of groups of dilated intrahepatic bile ducts embedded within a dense collagenous stroma. They usually measure less than 5 mm
and are typically multiple and scattered throughout the liver.  They are located within and at the edges of portal tracts and are not connected with the biliary system. Aggregations of BH may appear as larger solitary lesions on imaging.
Biliary hamartomas are detected incidentally at autopsy in 0.6% to 5.6% of cases. Biliary hamartomas are thought to develop from interrupted remodeling of the ductal plates during the late phase of embryologic development of the intrahepatic bile ducts.  Ductal plate malformation is involved in the genesis of BH, congenital hepatic fibrosis, and liver cysts in ADPKD, PLD, and Caroli disease. Moreover, BH are associated with each of these disorders,and there is evidence that cysts in both ADPKD and PLD arise from dilatation of the ductal plate malformation structures of BH.

On sonography, BH have been described as innumerable tiny hypoechoic or hyperechoic foci measuring less than 10 mm and distributed uniformly throughout the liver, and they may have a comet tail artifact.  Differences in echogenicity may be due to the size of the dilated bile duct component, which, at a certain size, would behave like other microcystic structures and show echogenicity. Below this size, their complex internal structure might attenuate the echo signal.

Figure 2. Low-power histologic specimen of a bile duct hamartoma. The lesion is lobulated with irregular, angulated bile ducts (large arrows) present in the background of fibrotic stroma (asterisk). The epithelial cells are single layered, flattened, or cuboidal (small arrow). Bile is shown in some ducts. The stroma contains neutrophils and histiocytes (hematoxylin-eosin, original magnification × 20).


On computed tomography, BH are depicted as multiple round, small hypoattenuating and nonenhancing areas distributed throughout the liver without a distinctive distribution pattern.
On MRI, BH are described as hypointense on T1-weighted images and hyperintense on T2-weighted images. On heavily T2-weighted images with a longer echo time, the signal intensity of the lesions remains high, allowing differentiation from liver metastasis.
Computed tomography and MRI did not help distinguish BH from small cysts associated with ADPKD.

The major clinical importance of BH is the propensity for misdiagnoses as multiple metastases, microabscesses, C albicans, and extrapulmonary P carinii infections. Metastases may be hypoechoic (eg, lymphoma) or hyperechoic (eg,colon and breast carcinoma). However, liver metastases are typically larger and variable in size and distribution, whereas BH are small and uniform in size and distribution.  Pyogenic microabscesses may appear as multiple widely scattered lesions similar in distribution to fungal microabscesses in immunosuppressed patients. A diffuse miliary pattern of pyogenic microabscesses may be seen in staphylococcal septicemia. Sonography may show either discrete hypoechoic nodules or poorly defined areas of distorted hepatic echogenicity with little or no enhancement through transmission. Sonographic imaging of patients with candidal infection may reveal lesions with alternating rings of hyperechogenicity and hypoechogenicity; however, a pattern of uniformly hypoechoic nodules is most common. Candida infection presenting as multiple echogenic foci may be mistaken for BH; however, these candidal foci show variable degrees of posterior acoustic shadowing, and this pattern occurs in later stages of infection, generally indicating early resolution.  In a patient with acquired immunodeficiency syndrome, extrapulmonary P carinii may present as numerous tiny hyperechoic foci in the liver,  which are similar to the appearance of BH.

In summary, whereas several acquired diseases may have an appearance similar to that of BH, in the context of ADPKD, BH should be considered high in the differential diagnosis of numerous tiny echogenic liver foci on sonography. Additionally, BH should be considered in the differential diagnosis of numerous tiny echogenic liver foci in PLD, congenital hepatic fibrosis, and Caroli disease.