Endoscopic ultrasound elastography: Current status and future perspectives

Abstract

Elastography is a new ultrasound modality that provides images and measurements related to tissue stiffness. Endoscopic ultrasound (EUS) has played an important role in the diagnosis and management of numerous abdominal and mediastinal diseases. Elastography by means of EUS examination can assess the elasticity of tumors in the proximity of the digestive tract that are hard to reach with conventional transcutaneous ultrasound probes, such as pancreatic masses and mediastinal or abdominal lymph nodes, thus improving the diagnostic yield of the procedure. Results from previous studies have promised benefits for EUS elastography in the differential diagnosis of lymph nodes, as well as for assessing masses with pancreatic or gastrointestinal (GI) tract locations. It is important to mention that EUS elastography is not considered a modality that can replace biopsy. However, it may be a useful adjunct, improving the accuracy of EUS-fine needle aspiration biopsy (EUS-FNAB) by selecting the most suspicious area to be targeted. Even more, it may be useful for guiding further clinical management when EUS-FNAB is negative or inconclusive. In the present paper we will discuss the current knowledge of EUS elastography, including the technical aspects, along with its applications in the differential diagnosis between benign and malignant solid pancreatic masses and lymph nodes, as well as its aid in the differentiation between normal pancreatic tissues and chronic pancreatitis. Moreover, the emergent indication and future perspectives are summarized, such as the benefit of EUS elastography in EUS-guided fine needle aspiration biopsy, and its uses for characterization of lesions in liver, biliary tract, adrenal glands and GI tract.

Keywords: Characterization; Elastography; Endoscopic ultrasound; Lymph nodes; Pancreas.

Figure 1

Benign and malignant pancreatic masses on endoscopic ultrasound elastography. A: A pancreatic teratoma is shown as heterogeneous soft (green) pattern (left: EUS elastography image; right: B-mode image); B: A pancreatic ductal adenocarcinoma appears stiffer (blue) than the adjacent normal pancreatic parenchyma, probably due to the presence of fibrosis and marked desmoplasia.

Figure 2

Combination of elastography and contrast-enhanced ultrasound in endoscopic ultrasound. A: A pancreatic ductal adenocarcinoma is demonstrated as a heterogeneous hard (blue) pattern; B: On contrast-enhanced endoscopic ultrasound, pancreatic ductal adenocarcinoma is hypo-enhancing.

Figure 3

Malignant Lymph nodes on endoscopic ultrasound elastography. A malignant lymph node is revealed as predominantly hard (blue). Arrows indicate infiltration. LN: Lymph node.

Figure 4

Endoscopic ultrasound elastography adds information to the B-mode evaluation of lymph nodes and can better guide a fine needle aspiration procedure by identifying stiffer (blue in the image) and thus, most suspicious regions for malignant infiltration. Arrow indicates needle tip.

Figure 5

Gastric carcinoma is shown as heterogeneously stiff pattern (blue) on endoscopic ultrasound elastography.

Figure 6

Gastrointestinal stromal tumor is revealed heterogeneous hard (blue) pattern on endoscopic ultrasound elastography.

Figure 7

Benign adrenal gland tumor is typically soft (green) on endoscopic ultrasound elastography (A) and hyper-enhancing on contrast-enhanced endoscopic ultrasound (B).