New Imaging Techniques: Endoscopic Ultrasound-Guided Elastography

Pancreatic cancer, autoimmune or chronic pancreatitis, beyond tissue diagnosis: Collateral imaging and clinical characteristics may differentiate them

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies and is developing into the 2^nd leading cause of cancer-related death. Often, the clinical and radiological presentation of PDAC may be mirrored by other inflammatory pancreatic masses, such as autoimmune pancreatitis (AIP) and mass-forming chronic pancreatitis (MFCP), making its diagnosis challenging. Differentiating AIP and MFCP from PDAC is vital due to significant therapeutic and prognostic implications. Current diagnostic criteria and tools allow the precise differentiation of benign from malignant masses; however, the diagnostic accuracy is imperfect. Major pancreatic resections have been performed in AIP cases under initial suspicion of PDAC after a diagnostic approach failed to provide an accurate diagnosis. It is not unusual that after a thorough diagnostic evaluation, the clinician is confronted with a pancreatic mass with uncertain diagnosis. In those cases, a re-evaluation must be entertained, preferably by an experienced multispecialty team including radiologists, pathologists, gastroenterologists, and surgeons, looking for disease-specific clinical, imaging, and histological hallmarks or collateral evidence that could favor a specific diagnosis. Our aim is to describe current diagnostic limitations that hinder our ability to reach an accurate diagnosis among AIP, PDAC, and MFCP and to highlight those disease-specific clinical, radiological, serological, and histological characteristics that could support the presence of any of these three disorders when facing a pancreatic mass with uncertain diagnosis after an initial diagnostic approach has been unsuccessful.

Endoscopic Ultrasound (EUS) Guided Elastography

Endoscopic ultrasound (EUS) is an essential technique for the management of several diseases. Over the years, new technologies have been developed to improve and overcome certain limitations related to EUS-guided tissue acquisition. Among these new methods, EUS-guided elastography, which is a real-time method for the evaluation of tissue stiffness, has arisen as one of the most widely recognized and available. At present, there are available two different systems to perform an elastographic evaluation: strain elastography and shear wave elastography. Strain elastography is based on the knowledge that certain diseases lead to a change in tissue hardness while shear wave elastography monitored shear-wave propagation and measures its velocity. EUS-guided elastography has shown in several studies high accuracy in differentiating benign from malignant lesions from many different locations, mostly in the pancreas and lymph nodes. Therefore, nowadays, there are well-established indications for this technology, mainly for supporting the management of pancreatic diseases (diagnosis of chronic pancreatitis and differential diagnosis of solid pancreatic tumors) and characterization of different diseases. However, there are more data on new potential indications for the near future. In this review, we will present the theoretical bases of this technology and we will discuss the scientific evidence to support its use.

Endoscopic ultrasonography: Enhancing diagnostic accuracy

Endoscopic ultrasound (EUS) is an essential technique for the management of several diseases. Over the years, new technologies have been developed because to improve and overcome certain limitations related to EUS guided tissue acquisition. Among these new methods, EUS guided elastography and contrast enhanced EUS has arisen as the most widely recognized and available. We will review in this manuscript the different techniques of elastography and contrast enhancement. Nowadays, there are well establish indications for advance imaging, mainly for supporting the management of pancreatic diseases (diagnosis of chronic pancreatitis and differential diagnosis of solid and cystic pancreatic tumors) and characterization of lymph nodes. However, there are more data on new potential indications for the near future.

Pancreatic Elastography Predicts Endoscopic Secretin-Pancreatic Function Test Result in Patients With Early Changes of Chronic Pancreatitis: A Prospective, Cross-Sectional, Observational Study

INTRODUCTION

The endoscopic pancreatic function test (ePFT) has been proposed for the evaluation of patients with suspected early chronic pancreatitis (CP) in the appropriate clinical context, but the cost and duration of the test limit its clinical applicability. Pancreatic secretion decreases as pancreatic fibrosis develops in CP. Pancreatic fibrosis can be quantified by endoscopic ultrasound-elastography (EUS-E). We aim at evaluating whether EUS-E correlates with and could replace ePFT for the evaluation of patients with suspected CP.

METHODS

A prospective, cross-sectional, and observational study of patients with clinical suspicion of CP and inconclusive EUS findings was conducted. EUS-E and ePFT were performed. Diagnosis of CP was supported if the ePFT result (bicarbonate peak) was abnormally low (<80 mEq/L). Correlation between EUS-E (strain ratio [SR]) and ePFT results was analyzed by linear regression. Diagnostic accuracy of EUS-E for CP was calculated using ePFT as a reference method.

RESULTS

Sixty-one patients were included and analyzed. The mean peak bicarbonate concentration at the ePFT was 63.8 ± 23.6 mEq/L, and it was abnormally low in 50 patients (82.0%). The mean SR was 3.85 ± 1.24. Correlation between SR and bicarbonate secretion was highly significant ( r = 0.715, P < 0.0001). Diagnostic accuracy of EUS-E for CP was 93.4%.

DISCUSSION

The degree of pancreatic fibrosis as evaluated by EUS-E correlates significantly with the secretin-stimulated pancreatic secretion of bicarbonate in patients with clinical suspicion of CP and inconclusive EUS findings of the disease. EUS-E could replace ePFT for the evaluation of these patients in clinical practice.

The expanding role of endoscopic ultrasound elastography

Endoscopic ultrasound (EUS) is an invaluable tool for assessing various GI diseases. However, using just the conventional B-mode EUS imaging may not be sufficient to accurately delineate the lesion's character. Using the principle of stress-induced tissue strain, EUS elastography (EUS-E) can help in the real-time sonographic assessment of the level of tissue stiffness or hardness of any organ of interest during a routine EUS procedure. Thus, EUS-E can better characterize the lesion's nature and highlight the more suspicious areas within an individual lesion. The most commonly studied lesions with EUS-E are the pancreatic lesions, namely, chronic pancreatitis, pancreatic cancer, and lymph nodes. However, EUS-E is gradually expanding its use for lesion characterization of the liver, bile duct, adrenals, gastrointestinal tract, and even therapy response. Moreover, the use of EUS-E along with other image enhancement techniques such as harmonic EUS and contrast-enhanced EUS can improve the accuracy of the diagnosis. However, several technical aspects need to be standardized before EUS-E can be truly used as a tool for "virtual biopsy". This review focuses on the various technical aspects of the use of EUS-E, it is established and expanding indications and an extensive outline of the various studies on EUS-E. We also discuss the current pitfalls and future trends in EUS-E.

Interventional endoscopy for abdominal transplant patients

Interventional endoscopy can play a significant role in the care and management of children pre-and post- abdominal solid organ transplantation. Such procedures primarily include endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasound (EUS), and balloon-assisted enteroscopy (BAE), though additional interventions are available using standard endoscopes (gastroscopes, colonoscopes) for therapeutics purposes such as endoscopic hemostasis. The availability of pediatric practitioners with the advanced training to effectively and safely perform these procedures are most often limited to large tertiary care pediatric centers. These centers possess the necessary resources and ancillary staff to provide the comprehensive multi-disciplinary care needed for these complex patients. In this review, we discuss the importance of interventional endoscopy in caring for transplant patients, during their clinical course preceding the potential need for solid organ transplantation and inclusion of a discussion related to endoscopic post-surgical complication management. Given the highly important role of interventional endoscopy in patients with recurrent and chronic pancreatitis, we also include a discussion related to this complex disease process leading up to those patients that may need pancreas surgery including total pancreatectomy with islet autotransplantation (TPIAT).

Role of endoscopic ultrasound in the field of hepatology: Recent advances and future trends

The role of endoscopic ultrasound (EUS) as a diagnostic and therapeutic modality for the management of various gastrointestinal diseases has been expanding. The imaging or intervention for various liver diseases has primarily been the domain of radiologists. With the advances in EUS, the domain of endosonologists is rapidly expanding in the field of hepatology. The ability to combine endoscopy and sonography in one hybrid device is a unique property of EUS, together with the ability to bring its probe/transducer near the liver, the area of interest. Its excellent spatial resolution and ability to provide real-time images coupled with several enhancement techniques, such as contrast-enhanced (CE) EUS, have facilitated the growth of EUS. The concept of “Endo-hepatology” encompasses the wide range of diagnostic and therapeutic procedures that are now gradually becoming feasible for managing various liver diseases. Diagnostic advancements can enable a wide array of techniques from elastography and liver biopsy for liver parenchymal diseases, to CE-EUS for focal liver lesions to portal pressure measurements for managing various liver conditions. Similarly, therapeutic advancements range from EUS-guided eradication of varices, drainage of bilomas and abscesses to various EUS-guided modalities of liver tumor management. We provide a comprehensive review of all the different diagnostic and therapeutic EUS modalities available for the management of various liver diseases. A synopsis of all the technical details involving each procedure and the available data has been tabulated, and the future trends in this area have been highlighted.

Endoscopic ultrasound assessment and tissue acquisition of mediastinal and abdominal lymph nodes

The differential diagnosis between benign and malignant lymph nodes (LNs) has a fundamental role in the characterization and staging of malignant conditions, as well as in subsequent patients’ management. All imaging modalities (i.e. computed tomography and magnetic resonance imaging) rely mainly on size; endoscopic ultrasound (EUS) criteria based on B-mode evaluation and Doppler features fail to adequately characterize with high specificity LNs nature. The introduction of EUS-elastography and contrast-enhanced harmonic EUS are useful techniques to increase the diagnostic yield in identifying metastatic LNs, to identify which suspicious LN should require pathological characterization and, finally, to target tissue acquisition. EUS-guided tissue acquisition (EUS-TA) is increasingly being used for diagnosing lymphadenopathy whenever the characterization modifies patients’ subsequent management and when no superficial LN is accessible. Since target therapy are currently available (i.e. lung cancer, breast cancer), EUS-TA of malignant LNs could be required to identify tumor biology. In this field, both fine needle aspiration and biopsy needles are able to guarantee accurate results with almost perfect specificity and sub-optimal sensitivity. We finally propose a diagnostic algorithm based on most recent, high-level evidence for the diagnostic approach to suspected LNs assessment.

Efficacy of Endoscopic Ultrasound Elastography in Differential Diagnosis of Gastrointestinal Stromal Tumor Versus Gastrointestinal Leiomyoma

BACKGROUND The diagnostic efficacy of endoscopic ultrasound (EUS) elastography for alimentary tract diseases remains uncertain. The aim of this study was to evaluate the utility of EUS elastography in differential diagnosis between the 2 most common subepithelium tumors of the digestive tract - gastrointestinal stromal tumors (GISTs) and gastrointestinal leiomyomas (GILs) - which cannot be differentiated by conventional EUS imaging. MATERIAL AND METHODS Electronic records were retrospectively reviewed from Jan 2015 to Jul 2019. Patients accepting EUS elastography with histopathological diagnosis of GISTs or GILs were included. The images of EUS elastography were analyzed by hue histogram in Photoshop. Hue values of RGB, R, G, and B channels of each group were acquired. We used the t test, ROC curve analysis, and binary logistic regression analysis for data post-processing. RESULTS We included 47 patients with GISTs and 14 with GILs. The mean±standard deviations (SD) of hue values were 20.25±0.72, -0.79±0.78, 20.79±1.68, 39.72±1.30 for GISTs and 20.80±0.46, 1.80±1.05, 28.39±2.15, and 31.95±2.60 for GILs of RGB, R, G, and B channels, respectively. The t test showed statistically significant differences in mean hue values between GISTs and GILs in B and G channels, but not in RGB and R channels. The area under the ROC curve combining B and G values was 0.723. Binary logistic regression analysis suggested no statistically significant difference in ability to differentiate between GISTs and GILs with B and G values (P>0.05). CONCLUSIONS There was insufficient evidence to support the application of quantitative EUS elastography for differential diagnosis of GISTs and GILs in this study.

Endoscopic ultrasound-based multimodal evaluation of the pancreas in patients with suspected early chronic pancreatitis

BACKGROUND

Diagnosis of early chronic pancreatitis is a clinical challenge and hindered by the lack of a gold standard. Endoscopic ultrasound (EUS) and the endoscopic pancreatic function test (ePFT) are the most sensitive morphological and functional methods in this setting. EUS-elastography allows for the quantification (strain ratio) of pancreatic fibrosis, and the dynamic evaluation of the main pancreatic duct compliance provides additional information. We developed a multimodal EUS-based approach for the evaluation of the pancreas by integrating these four methods in a single procedure.

OBJECTIVE

We aim to describe morphological and functional pancreatic abnormalities in patients with clinical suspicion of chronic pancreatitis and inconclusive EUS findings by using the multimodal EUS-based approach.

METHODS

This was a prospective, cross-sectional, observational study of patients with clinically suspected chronic pancreatitis and indeterminate EUS criteria of the disease. EUS criteria of chronic pancreatitis, quantitative pancreatic elastography, ePFT and compliance of the main pancreatic duct were evaluated in a single procedure.

RESULTS

In total, 53 patients with 3-4 EUS criteria of chronic pancreatitis were included (mean age 39.7 years, 29 male). Strain ratio was abnormally high in all patients. Peak bicarbonate concentration was decreased in 43 patients (81.1%) and the main pancreatic duct compliance was reduced in 41 patients (77.3%). Some 34 patients (64.1%) had abnormal results at EUS, elastography, ePFT and compliance of the main pancreatic duct.

CONCLUSIONS

A multimodal EUS-based test for the morphological and functional evaluation of the pancreas is presented, which allows detecting mild pancreatic abnormalities in patients with suspected early chronic pancreatitis. The presence of abnormal morphological and functional evaluation of the pancreas could support the clinical suspicion of early chronic pancreatitis in the appropriate clinical setting.

Endoscopic ultrasonography elastography in the diagnosis of intrapancreatic ectopic spleen: A case report

BACKGROUND

Intrapancreatic accessory spleen (IPAS) mimics a pancreatic neoplasm on imaging studies, and due to the lack of radiological diagnostic criteria, patients undergo unnecessary distal pancreatectomies. Endoscopic ultrasonography (EUS) is a reliable and efficient diagnostic modality for pancreatic diseases. However, no EUS criteria have been established for IPAS. We present the EUS-elastography image of IPAS, which may minimize the chance of misdiagnosis in the future.

CASE SUMMARY

A 50-year-old man was referred for an EUS evaluation after computed tomography showed a hypervascular enhanced mass in the tail of the pancreas, which indicated a neuroendocrine neoplasm. EUS elastography demonstrated that the lesion of interest covered no more than 25% of the region of interest. The patient underwent distal pancreatectomy. However, the resected tissue was evaluated, and the patient was finally diagnosed with IPAS.

CONCLUSION

IPAS should be considered in patients with suspected pancreatic neuroendocrine tumors of the pancreatic tail before surgery is performed. The differentiation between IPAS and pancreatic neuroendocrine tumors can be demonstrated using EUS-elastography.

Differential diagnosis of solid pancreatic masses

Solid pancreatic lesions include mainly adenocarcinoma, neuroendocrine tumors pancreatic cystic neoplasms with solid component, solid pseudopapillary tumor, pancreatoblastoma, pancreatic lymphoma, and pancreatic metastasis. The most frequent pancreatic lesion is the adenocarcinoma, representing between 70% and 95% of all solid pancreatic neoplasm. The diagnosis of these lesions can be a challenge and currently, there are different imaging techniques such as CT scan, EUS and MRI with high sensitivity and specificity. The most widely used technique for the initial evaluation is the CT scan with a sensitivity between 76% and 92% for the diagnosis of pancreatic cancer. The EUS has a sensitivity for the detection of pancreatic lesions of around 98% and is accepted to be the most sensitive technique for the detection of small pancreatic tumors (<2 cm). The MRI, with a very high soft-tissue contrast resolution, provides an accuracy in the detection and staging of adenocarcinoma of 90-100%. A multimodality approach is usually necessary in patients with clinical suspicion of pancreatic lesion. The EUS is required for the local evaluation of the relation of the lesion with vessels and for tissue acquisition and the CT scan and/or MRI is usually required for the local and distance staging in case of pancreatic cancer. The purpose of this review is to provide an overview of solid pancreatic lesions and the role of the different imaging techniques in their evaluation.

Do we need elastography for EUS?

We recently introduced a series of papers “What should be known prior to performing EUS exams.” In Part I, the authors discussed which clinical information and whether other imaging modalities are needed before embarking EUS examinations. In Part II, technical controversies on how EUS is performed were discussed from different points of view. In this article, important practical issues regarding EUS elastography will be raised and controversially discussed from very different points of view.

Echoendoscopy with elastography in mediastinal lymph nodes

Elastography is a widely used procedure in conventional ultrasonography that has recently been incorporated in echoendoscopy. This is an innovative and promising technology that aims to increase the negative predictive value of endoscopic ultrasonography and fine-needle aspiration punctures. It is useful for directing punctures in suspect areas and, consequently, improves diagnostic performance. This is a non-invasive technique, easy to perform, without additional costs or complications. The main indications are the analysis of solid pancreatic masses, lymph nodes, subepithelial lesions, lesions in the left hepatic lobe and in the left adrenal. Negative or inconclusive cases of fine-needle aspiration can be submitted to elastography when there is a strong suspicion of malignancy. Elastography has a high precision for the differential diagnosis of solid masses and in difficult-to-access anatomic sites, as well as in mediastinal lymph nodes and pancreatic tumors. The procedure is based on the degree of tissue elasticity measurement, with a good correlation between the elasticity index and histopathological features. We report the case of four patients evaluated by echoendoscopy and qualitative elastography who had differential diagnoses in mediastinal lymph nodes: sarcoidosis, lymphoma, histoplasmosis and esophageal neoplasia.

Early pancreatic cancer - The role of endoscopic ultrasound with or without tissue acquisition in diagnosis and staging

Pancreatic cancer (PC) is one of the deadliest cancers with a 5-year overall survival of less than 6%. Due to its insidious clinical course and unspecific symptoms, the diagnosis is usually late, with only 15-20% patients presenting with potentially curable disease. It is, therefore, extremely important to identify patients with PC at early stages of the disease when tumors may be amenable to surgical resection. For unresectable and borderline resectable PC it is consensual to perform a biopsy to have a cyto/histological confirmation of malignancy before treatment. However, for patients presenting with promptly resectable disease, the role of biopsy is more debatable. There are, in the literature, arguments both for and against the usefulness of a preoperative biopsy. Endoscopic ultrasound (EUS) is an important technique assisting in the diagnosis and staging of PC. EUS-guided tissue acquisition is a well-established tool to demonstrate the malignant nature of a pancreatic lesion. This review focuses on the role of EUS in the diagnosis and staging of PC, and highlights the controversy related to the role of EUS-guided tissue acquisition in the preoperative assessment of patients presenting with promptly resectable tumors (early PC).