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 17 November 2017

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Endoscopic ultrasound

Ian Penman


1. Endoscopic ultrasonography overview

Ian D. Penman

Top of page Introduction  Next section

EUS has come a long way in twenty or so years since its first description. Once the preserve of a dedicated and 'lucky' few, working in the rarefied atmosphere of academic centers, many gastroenterologists regarded EUS as esoteric and unlikely to last the course. Nowadays even the most skeptical accept that EUS is here to stay, and it has now earned its place in mainstream endoscopy throughout the world. While not everything relating to EUS is black and white yet, the shades of gray are certainly becoming clearer.

Top of page History  Previous section Next section

EUS began in the early 1980s with rather cumbersome and unwieldy mechanical radial instruments, with which pioneers developed the technique, defining anatomy and correlating images with CT, intraoperative findings, and results of surgical pathology. Artefacts and pitfalls of imaging were carefully studied and image quality improved dramatically with new transducers and a greater range of scanning frequencies. This progress was matched by parallel improvements in endoscopic optics and scope handling characteristics. At the same time as Olympus were refining radial mechanical instruments, Hitachi/Pentax developed the first curved linear array (CLA) echoendoscope. This instrument introduced electronic transducers to EUS, allowing color Doppler imaging and subsequently the ability to perform real-time EUS-guided tissue acquisition by fine-needle aspiration cytology.

Steady progress in research and development has now led to a considerable range of instruments capable of providing exquisite high-resolution images in a wide range of clinical settings. As well as mechanical radial instruments there are high-quality CLA echoendoscopes with large operating channels which allow therapeutic procedures, through-the-scope catheter probes imaging at up to 30 MHz, and, most recently, electronic radial instruments, the latest models of which allow 360° imaging. With parallel advances in ultrasound processors the capabilities and potential of EUS continue to grow, with modalities such as tissue harmonics, contrast enhancement agents, and elastography yet to be fully explored.

Top of page Current applications  Previous section Next section

Cancer staging remains the workhorse of EUS. While advances in multi-detector CT scanning and MRI may diminish much of the current superiority of EUS for locoregional (T, N) tumour staging, EUS retains a key role in staging cancers of the esophagus, stomach, pancreas and rectum. Outwith the gastrointestinal tract perhaps one of the most clearcut and least controversial roles of EUS is in the mediastinal staging of non-small cell lung cancer and the evaluation of posterior mediastinal masses. EUS is invaluable in the assessment of submucosal lesions, thickened gastric folds, and a variety of benign disorders, including choledocholithiasis, microlithiasis, and chronic pancreatitis. Perhaps, however, the importance of EUS has been cemented by its ability to provide high-quality tissue samples of excellent diagnostic accuracy and relative safety. This is especially true in situations such as small lymph nodes undetected by other means and in lesions inaccessible by other routes. The recent development of core biopsy needles is another exciting step forward, allowing detailed immunohistochemical and molecular studies to be performed on tissue samples. EUS is ideally placed to play a key role in this translational research, combining the power of microarray and proteomic technology with the ability to obtain tissue samples from otherwise often inaccessible targets.

Top of page Therapeutic EUS  Previous section Next section

Although EUS is still thought of as relatively new, it has grown into a mature technology, yet the goal of truly therapeutic EUS seems to have been a long time coming. Celiac plexus neurolysis is simple and well established and the place of EUS in drainage of pancreatic pseudocysts is increasingly clear. As for other procedures, case reports and small case series have allowed us a glimpse of the future but large studies of the efficacy and safety of EUS-guided procedures such as tumor ablation, delivery of antitumor agents, biliary drainage, and creation of anastomoses are still awaited. Surely their time will come in the near future?

Top of page Teaching and training EUS  Previous section

The learning curve is steep, training is long, demand is finite, and equipment is expensive. It is likely, therefore, that for the foreseeable future EUS will remain largely within the realm of academic or regional centers. Whether or not all gastroenterology trainees should undertake EUS is a difficult question. If only some are to be trained, should it be those with an interest in pancreatico-biliary endoscopy, those with an interest in gastrointestinal cancer, or others? Indeed, should we just train gastroenterology fellows? In some countries EUS is performed routinely by gastrointestinal surgeons or radiologists. What should constitute a training curriculum for EUS is another issue yet to be satisfactorily resolved. What is clear is the ongoing need for high-quality training in EUS, as this procedure is here to stay, will continue to evolve, and is likely to remain an integral part of gastrointestinal endoscopy for many years to come.

The chapters in this volume address EUS instrumentation and technique, the principles of EUS cancer staging, the role of EUS in evaluating submucosal tumors, lung cancer, and mediastinal masses, and, finally, benign and malignant pancreatic or biliary disease. They are written by some of the most respected experts in this field and provide detailed up-to-date and state-of-the art reviews which I hope you find informative and enjoyable.

Copyright © Blackwell Publishing, 2005

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Introduction
History
Current applications
Therapeutic EUS
Teaching and training EUS
Synopsis
Introduction
Radial and linear endosonographic probes
Contrast-enhanced ultrasonography
Catheter-based EUS probes (miniprobes)
  Miniprobe technique
  Miniprobes in cancer
  Other uses of miniprobes
  Miniprobe limitations
Needles and accessories for EUS
  Fine-needle aspiration
   Different types of needles
   FNA technique
   Accuracy and safety
  Core tissue biopsies
   Technique
   Accuracy and safety
Outstanding issues and future trends
References
Synopsis
EUS for cancer staging
Esophageal cancer staging with EUS
  Esophageal cancer TNM staging
  Technique for performing EUS staging of esophageal cancer
  EUS of stenotic esophageal tumors
  EUS evaluation of superficial tumors
  EUS evaluation of lymph nodes
  EUS-FNA of peri-esophageal lymph nodes
  Accuracy and limitations of EUS staging of esophageal cancer
  EUS re-staging of esophageal cancer after chemoradiation
  Impact of EUS staging on esophageal cancer management
Gastric cancer staging with EUS
  Gastric cancer TNM staging
  EUS staging of advanced gastric adenocarcinoma
  EUS staging of early gastric adenocarcinoma
  EUS staging of gastric MALT lymphoma
Rectal cancer staging with EUS
  Rectal cancer TNM staging
  Pathologic staging of rectal cancer
  Surgical management of rectal cancer
  Management algorithm for rectal cancer (Fig. 17)
  Technique for performing EUS rectal cancer staging
  EUS staging of rectal cancer
  Accuracy of EUS in staging rectal cancer
  EUS vs. CT and MRI for rectal cancer staging
  EUS/FNA for rectal cancer lymph node staging
  Stenotic rectal tumors
  Rectal EUS staging after radiation therapy
  Colon cancer staging with EUS
Anal cancer staging with EUS
Pancreatic cancer
  Staging of pancreatic cancer
  EUS staging of pancreatic cancer (Figs 12,13)
  Combination of EUS and CT/MRI for pancreatic cancer staging and determining resectability
  EUS-FNA for staging pancreatic cancer
  Recommendations for EUS staging of pancreatic cancer
Ampullary cancer
Extrahepatic bile duct cancer
Future trends and outstanding issues
References
Synopsis
Introduction
Endoscopic and EUS examination
GISTs
  Origin and development of GISTs
  Molecular biology of GIST: c-kit
  CD34 and other immunohistochemistry
  Clinical features
  Pathology
  Predicting malignant behavior: role of molecular markers
  Predicting malignant behavior: role of EUS
  Tissue sampling of GISTs
  EUS-guided fine-needle aspiration
  Therapy: surgery
  Therapy: imatinib
Leiomyomas
  Clinical features and diagnosis
  EUS features
Lipomas
  Clinical features and diagnosis
  EUS features
Granular cell tumors
  Clinical features
  Pathology
  Endoscopic and EUS features
  Treatment of granular cell tumors
Duplication cysts
  Clinical features
  EUS features
  Treatment of duplication cysts
Carcinoid tumors
  Clinical features and pathology
  Biochemistry
  Endoscopic and EUS features
  Appendiceal carcinoids
  Ileal carcinoids
  Rectal carcinoids
  Gastric and duodenal carcinoids
Ectopic pancreas ('pancreatic rest')
  Clinical features
  EUS features
Extrinsic compressions
Varices
Future trends and outstanding issues
References
Synopsis
Morbid anatomy
  Pancreas
  Portal vein
  Common bile duct
Endosonographic anatomy
Performing EUS of the pancreas and biliary tree
  Body and tail of pancreas
   Radial EUS
   Linear EUS
  Head and uncinate process of pancreas
   Radial EUS
   Linear
Benign biliary disease
  Choledocholithiasis
  Choledochal cysts
  Primary sclerosing cholangitis (PSC)
Malignant biliary disease
  Ampullary carcinoma
  Cholangiocarcinoma
  Carcinoma of the gallbladder
Benign pancreatic disease
  Pancreatitis
   Acute pancreatitis
   Chronic pancreatitis
   Autoimmune pancreatitis
Cystic lesions of the pancreas
  Pseudocysts
  Cystadenomas
   Serous cystadenoma
   Mucinous cystadenoma
   Solid-cystic pseudopapillary tumor
   Intraductal mucin-producing tumor/neoplasm (IPMT/N)
   Mucinous cyst adenocarcinoma
Solid tumors of the pancreas
  Adenocarcinoma
   Screening for adenocarcinoma
  Neuroendocrine tumors
  Metastases
Training in pancreatico-biliary EUS
Outstanding issues and future trends
References
Synopsis
Non-invasive imaging modalities
  Chest CT
  Positron emission tomography
Invasive staging
Endoscopic ultrasound-guided fine-needle aspiration
  Accuracy for diagnosing malignancy
  EUS and identification of metastatic disease
  EUS technique
  Limitations of EUS-FNA
Combined minimally invasive staging with endoscopic ultrasound and endobronchial ultrasound
Outstanding issues and future trends
  EUS-FNA and molecular markers in lung cancer
References

Blackwell Publishing


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