Upper GI endoscopy is the basic skill that all endoscopists should master. Adequate examination requires careful preparation and well-trained endoscopic technique. Before initiating endoscopy, clinical indications, the subject's medical condition, informed consent, endoscopic equipment, and the administration of premedication should all be examined. Detailed endoscopic procedures and techniques, from insertion to removal of the endoscope, were explained in this session.

Complete endoscopic evaluation requires proper knowledge and training regarding the endoscopy unit, anatomic landmarks, basic techniques for complete evaluation of each anatomic segment from esophagus to duodenum, and any lesion characteristics that might be encountered during endoscopy. Special care should be taken to detect any lesions located in blind spots.

Pathological diagnosis of GI lesions can be reached using biopsy specimens from lesions. Communication between the attending endoscopist and pathologist should clearly state what clinical information was found during the endoscopic examination. Obtaining adequate biopsy specimens is the most important step in reaching an accurate diagnosis. The topics covered included general principles for biopsy, types and characteristics of forceps, tips for performing biopsy at various locations, and possible complications that accompany biopsy.

Documentation of the endoscopic examination allows for recordkeeping and communication between medical personnel. Endoscopy provides visual information that is most accurately documented using photos or movie clips. At least eight photos should be taken from predetermined sites during endoscopy, to assess the adequacy of the endoscopic examination. Description of endoscopic findings requires detailed information regarding location, size, and morphologic characteristics of any lesions.

Barrett's esophagus is diagnosed if columnar lined esophagus (CLE) is detected during the endoscopic examination, and specialized intestinal metaplasia, including goblet cells, is confirmed at the histopathological examination. Recently, questions have been raised regarding the necessity of obtaining biopsy specimens in Korean cases that have a very low possibility of esophageal adenocarcinoma.1 In this session, the definition and diagnosis of Barrett's esophagus, CLE in lower esophagus, and the controversy regarding the necessity of biopsy for confirmation and risk assessment in cases with suspected Barrett's esophagus were presented.

Subepithelial masses are often found during screening endoscopy of participants in the National Cancer Screening Program. These incidentally detected subepithelial masses are typically small, and the chance of malignancy is considered quite low. In this session, tips for endoscopic evaluation and characteristic endoscopic ultrasound (EUS) findings that are useful for differential diagnosis were presented. Although obtaining a tissue specimen is quite difficult, the "bite-on-bite biopsy" technique, strip biopsy, fine needle aspiration, or core biopsy can all be used for tissue acquisition. Treatment should be guided by risk stratification, using the size of the tumor and mitotic index. Benign lesions, including lipoma, heterotopic pancreas, and cysts no longer require surveillance endoscopy.

Glandular atrophy and intestinal metaplasia are considered premalignant conditions in the stomach, although endoscopic diagnosis of the lesions has low sensitivity and specificity. Moreover, interobserver agreement regarding the presence and severity of glandular atrophy is not high, even among experienced endoscopists. In this topic, endoscopic classification of the atrophy and guidelines for risk stratification were reviewed. Surveillance techniques and the Helicobacter pylori treatment strategy were discussed as methods to prevent or potentially reverse these conditions.

Clinicians use biopsy specimens to reach a definitive diagnosis for gastric lesions, but they often receive pathological reports describing cellular atypia, atypical glands, or regenerating atypism. Vienna classification has been introduced to reduce the discrepancy in pathological diagnoses provided by Western and Japanese pathologists.2 Atypical cells or regenerating atypia can now finally be diagnosed as an inflammatory condition, adenoma, or adenocarcinoma. Thus, communication between pathologist and endoscopist is essential, and a strategy for reaching a definitive diagnosis is usually needed (depending on the suspicion of malignancy), which potentially includes follow-up biopsy or endoscopic resection.

Incidentally or intentionally swallowed foreign material can be trapped by the narrow points of the esophagus, and may cause serious complications. In this session, basic evaluations and procedures were presented to address this emergency situation. Indications and timing of endoscopic removal may differ according to the type, size, and shape of the ingested material. Preprocedural evaluation and assessment, including history taking, physical examination, and radiological evaluation, are all essential for safe and successful procedure. The principle goal of the endoscopic procedure is rapid, accurate, and safe removal of the ingested material. Various specialized endoscopic techniques and accessories are used, depending on the type and shape of foreign body, and overtube insertion or general anesthesia is often required for safe procedures. Prevention and management of complications during, or after, the procedure is essential.

Peptic ulcers are still the most common cause of upper GI bleeding, although the incidence is decreasing thanks to proton pump inhibitor use and H. pylori eradication. Mallory-Weiss syndrome, bleeding from vascular anomaly, or upper GI tract malignancies are also important causes of upper GI bleeding. Blatchford or Rockall scores for clinical assessment, and Forrest classification for endoscopic evaluation, can all be helpful for risk assessment. Endoscopic procedures and medical management for these conditions are discussed. Endoscopic procedures using injection, clips, ligation, or coagulation were also discussed.3

Acute variceal bleeding is a potential life-threatening complication of liver cirrhosis. Endoscopic treatment of active bleeding, and adequate preventive measures, are essential for preventing deterioration of the patient's condition. In this session, severity assessment and obtaining hemodynamic stability, medical therapy including administration of splanchnic constrictors (e.g., terlipressin or octreotide), and administration of prophylactic antibiotics were discussed.4 Since endoscopic variceal ligation is the main therapy for acute variceal bleeding, it should be performed as soon as the patient becomes hemodynamically stable. Endoscopic treatment for gastric varices, salvage therapy after failure of endoscopic hemostasis, including balloon tamponade, transjugular intrahepatic portosystemic shunt, balloon-occluded retrograde transvenous obliteration, and surgical treatment options were also presented.

Ingestion of acid or alkaline substances causes serious caustic injury to the esophagus and stomach. The nature and degree of injury is determined by the type (acid vs. alkali), amount, concentration, and physical status (solid vs. liquid) of the ingested substance, as well as the duration of its contact with the GI tract mucosa. Details of substances causing caustic injury, pathophysiology, clinical presentation, endoscopic evaluation, patient management during the acute phase, and measures to prevent stricture were all described.5

Hong and Lim6 described how proper prerequisites and a tailored bowel preparation should be performed for all colonoscopy procedures. Modulation of antithrombotic agents should be considered based on the procedure-related bleeding risk and any potential thromboembolic risks associated with discontinuation of the medication. The proper choice of sedation, bowel cleansing, and diet modification should be based on patients' underlying disease, age, and medication intake. Education of patients are important for proper bowel preparation.

When initiating colonoscopy, the main challenge is to insert the colonoscope without pain or complication. To achieve this goal, endoscopists need to understand the structure of the colon, as well as insertion techniques such as right turn shortening, hooking the fold, and sliding. In order to pursue optimal colonoscopy, endoscopists should be fully aware of the limitations of colonoscopy. Optimal withdrawal techniques involve examination of the proximal sides of the ileocecal valve, all flexures, all haustral folds, and the rectal valves. Average withdrawal time of more than six minutes is recommended. Dynamic position change improves the adenoma detection rate.7 Efforts to minimize blind spots during colonoscopy should also be continued.

Cohen8 addressed the impact of tissue sampling on endoscopy efficiency in his review. Tissue sampling can be a tedious and time-consuming process, although accurate sampling remains a critical component of what we do, and is occasionally the most important component of an endoscopic procedure. Efforts to improve efficiency in tissue sampling will have an impact on not only endoscopic time management, but also costs and patient outcomes.8

It is important that reports of colonoscopy should include a certain number of illustrations, as these will provide confirmation that the whole of the colon had been examined thoroughly.9 The following key subject areas should be included in colonoscopy reports: patient demographics and history, assessment of patient risk and comorbidity, procedure indication(s), technical description of the procedure, colonoscopy findings, assessment, interventions/unplanned events, follow-up plan, and pathology.10

During colonoscopy, estimation of the depth of invasion in early colorectal lesions is crucial for adequate therapeutic management. Magnifying chromoendoscopy (MCE) has been proposed and used for these estimations. Determination of invasive or noninvasive patterns using MCE is a highly effective in vivo method for predicting the depth of invasion of colorectal neoplasms.11

Koo12 described how image-enhanced endoscopy (IEE) can highlight the lesion, which can improve colorectal adenoma detection rate and diagnostic accuracy. Equipment-based IEE such as narrow band imaging (NBI), Fuji intelligent chromo endoscopy (FICE), and I-Scan are all used to observe the mucosal epithelium, with good visualization of the microstructure and capillaries of the lesion, and are also helpful in the detection and differential diagnosis of colorectal tumors.

The new generation of high-definition endoscopes with electronic filter technology provides an opportunity to visualize mucosal inflammation in greater detail. Application of these new technologies in inflammatory bowel disease (IBD) is in its infancy, but the benefits are beginning to be appreciated. Assessment of both dysplasia and inflammation may benefit from the use of high-definition endoscopy with filter technology. In addition, the advent of confocal laser endomicroscopy provides an opportunity to explore real-time histology, thus redefining our understanding of the nature and pathogenesis of inflammation in IBD.13

Confocal endomicroscopy, an adaption of confocal laser scanning microscopy, and endocytoscopy, an adaption of white-light microscopy, have both been introduced into the endoscopic armamentarium in the past decade. Both techniques yield on-site histological information, and multiple trials have demonstrated their ability to obtain and interpret microscopic images from the GI tract during endoscopy. Such microscopic information has been successfully used by experts to minimize sampling error using "smart," microscopically targeted biopsies, and to guide endoscopic interventions.14

Electrosurgical units (ESUs) and snares are the most important devices for performing colonic polypectomy. Various types of ESU and snares have been developed, although ideal ESUs and snares are not yet available. Therefore, proper devices must be chosen according to the characteristics of the lesion. Endoscopists should have a comprehensive understanding of the basic principles of ESU, optimal techniques to minimize the complications of colon polypectomy, such as bleeding or perforation, and the ability to obtain suitable tissue samples for histological review. Modern ESUs have microprocessor-controlled feedback mechanisms, which can vary generator output in response to changes in tissue resistance, potentially reducing the risk of stalling during resection of a large volume of captured tissue or a thick stalk. However, this theoretical advantage has not been well studied in humans.15 There is little uniformity, and no standardization, regarding ESU settings used for polypectomy. Suggested generator settings for various ESUs and procedures have been described.15

Safe snare polypectomy requires the ability to break off a polyp, while achieving hemostasis and maintaining the integrity of the colon wall. Conventional snare polypectomy is a powerful technique for removal of colon polyps without submucosal solution injections. Snares are available in a wide variety of shapes and sizes, and the method of removal is determined by the shape and size of the polyp. There are many different types of snares, each with specific advantages, which can be chosen depending on the situation. Oval and hexagonal snares are most commonly used. A barbed snare can be used when tissue is hard to grasp, as can be the case with flat or sessile polyps, or when the snare slipping off the polyp seems to be an issue. Crescent snares are often used in endoscopic mucosal resection (EMR). A rotatable snare is useful when the snare initially comes out of the scope in such a way that is not optimal for snaring the polyp, and therefore must be rotated to a more suitable angle. A miniature snare can be used for the cold snaring of smaller polyps, or for removal of a small amount of residual tissue after piecemeal polypectomy. Use of a combination snare-injection needle enables rapid injection prior to opening the snare, and avoid the need to change out the injection needle wire for the snare (iSnare system).16 Endo-loops and clips can be used for prevention of post-polypectomy bleeding. The endo-loop, a detachable oval-shaped nylon snare, is deployed in the same way as a standard snare but is then tightened around the stalk or base of the polyp, prior to polypectomy.16

Endoscopic piecemeal mucosal resection (EPMR) and endoscopic submucosal dissection (ESD) are resection techniques used for colon polyps larger than 2 cm. EPMR is a relatively safe procedure and can be easily performed, although the recurrence rate is high (3% to 29%), and examining the histopathologic status of resection margin is difficult. However, ESD can be performed for en bloc resection of lesions and has a low recurrence rate, and the exact histopathologic status of resection margin can be examined. Unfortunately, ESD has a longer procedure time and a higher perforation rate (1.4% to 10.0%). However, if en bloc resection is required, even though the risk of complication is high, ESD should be chosen for treatment of colon polyps larger than 2 cm.17 Otherwise, EPMR can be performed for laterally spreading tumors larger than 2 cm.

After colonoscopic polypectomy, there are often complications such as bleeding, perforation, and postpolypectomy syndrome. Bleeding usually occurs between 1 and 14 days after polypectomy. The incidence of postpolypectomy bleeding varies from 0.19% to 24%, and perforation increases with age and the presence of diverticular disease. Delayed perforation is an indication for surgery. Postpolypectomy syndrome occurs in 0.5% to 2% of polypectomies, and is common after the removal of large (>2 cm) sessile polyps. Transmural burn in this syndrome does not cause actual perforation, although its symptoms can resemble localized perforation.18

Novice endoscopists should first observe and assist at colorectal ESD procedures, increase their skill and knowledge of ESD by performing simulations using animal models, and attend a live demonstration before starting colorectal ESD. Colorectal ESD is recommended after the endoscopist can safely perform gastric ESD, and is familiar with managing complications of gastric ESD. Starting with the lesion of the gastric antrum, under an experienced endoscopist's supervision, is recommended. However, persons with adequate experiences in the treatment of complications can begin performing colorectal ESD without experience in gastric ESD.

In obstructive colorectal cancer, resolving the occlusion is relatively easy using self-extending metal stents (SEMSs). However, there are still complications to be addressed, such as perforation, migration, and reocclusion. The length of SEMS should be approximately 3 to 4 cm longer than the length of the stenosis, and should be inserted fluoroscopically. To avoid perforation, endoscopists should limit the amount of air insufflation used during the procedure, especially in patients with dilated cecum, as well as avoid dilation before or after stent insertion.

EUS is superior to magnetic resonance imaging in differentiating between T1 and T2 rectal cancers. EUS-guided fine-needle aspiration or biopsy is useful for metastatic lesions of unknown origin in perirectal area, as well as a tissue diagnosis of subepithelial tumors, such as GI stromal tumors. Successful EUS-guided transcolonic and transrectal drainage of abdominopelvic abscesses has been reported.

Endoscopic balloon dilation is used for benign colorectal strictures, including postoperative anastomotic strictures and Crohn's disease with stricture. The balloon is positioned under visual control or fluoroscopy in the stricture, and inflated with water to attain a gradually increasing diameter. Inflation time varies from 1 to 3 minutes. The procedure is repeated until the colonoscope can pass through the stricture.19

There is no current consensus regarding which diagnostic codes, such as benign or malignant, should be given to colorectal mucosal cancers and carcinoids. No unified definition of colonic mucosal cancer exists, since it includes intraepithelial carcinoma, carcinoma in situ, and intramucosal carcinoma. Despite debates regarding colonic mucosal cancer, a recent trend has emerged, using D01 coding of carcinoma in situ instead of C coding.20 Thus, there is an urgent need for unified consensus through further research. Traditionally, carcinoid tumors have been known as low grade, malignant tumors of neuroendocrine origin. In 2000, the World Health Organization (WHO) suggested that carcinoids be referred to as well-differentiated neuroendocrine tumors (NETs). This convention was updated by WHO in 2010, according to the differentiation and malignant potential, resulting in NETs being classified as NET grade 1, grade 2, and neuroendocrine carcinomas. They suggested that NETs have malignant potential in accordance with histopathologic characteristics, and therefore WHO recommended the behavior code of NETs as malignant. However, the European Neuroendocrine Tumor Society (ENETS) proposed that the behavior of NETs be graded according to histopathologic features as benign, benign or low grade malignant, low grade malignant, and high grade malignant. As well, the American Joint Committee on Cancer (AJCC) has suggested that topography codes of NETs should be defined as malignant. Korean Standard Classification of Diseases (KCD) has also described the different coding of carcinoids (NETs). Therefore, discrepancies exist in the behavioral descriptions and coding systems used by the WHO, ENETS, AJCC, and KCD.21 A universal, appropriate diagnostic coding system should be prepared, based on either multicenter studies or social consensus meetings.

Safe and successful endoscopic retrograde cholangiopancreatography (ERCP) is important for both patients and endoscopists. This session dealt with the preparation before ERCP, ERCP in patients with high risk, and the importance of choosing the guide wire.22 The guide wire session included the following contents: a detailed introduction to the many kinds of guide wire, the role of wire-guided cannulation for the reduction of post-ERCP pancreatitis (PEP), and guide wire related complications.

This session covered selective cannulation and endoscopic sphincterotomy (EST), which are basic techniques for therapeutic ERCP. For selective cannulation, understanding the anatomy around the ampulla of Vater (AOV) is necessary, and using a pull-type sphincterotome is helpful. If selective cannulation is not successful, changing the technique is recommended. If patients are stable, halting the procedure and repeating ERCP after 1 to 2 days is another option. The basic EST technique was introduced as standard EST using a pull-type sphincterotome.

Selective cannulation is essential for ERCP, although it is sometimes rather difficult to make the desired duct using standard techniques with cannula or pull-type sphincterotome. Thus, precut and needle-knife fistulotomy are sometimes necessary for selective cannulation. This topic included the complications and risk factors of failed selective cannulation, precut access using the needle-knife, and transpancreatic septostomy.

Endoscopists regularly encounter congenital anomalies that make selective cannulation difficult. This topic introduced anomalies such as ectopic major duodenal papilla, anomalous union of the pancreatobiliary junction, choledochal cyst, and pancreas divisum. This session also dealt with indications and methods for minor papilla cannulation and sphincterotomy.

PEP is the most common post-ERCP complication, and every endoscopist should attempt to reduce the incidence of PEP. This topic introduced the high-risk group for PEP, the ERCP technique for the prevention of PEP, and various types of drugs for preventing PEP. Among the ERCP techniques, basic ERCP techniques for the prevention of PEP, wire guided cannulation, precut sphincterotomy, and pancreatic duct stenting were introduced. Drugs that can be used to prevent PEP include protease inhibitor (gabexate, ulinastatin, and nafamostat), somatostatin, and nonsteroidal anti-inflammatory drugs.

Post-ERCP bleeding is not common, and is graded as minor, moderate, and severe. This session dealt with the risk factors, prevention, and treatment of post-ERCP bleeding. Definite risk factors included coagulopathy, anticoagulation within three days, cholangitis before procedure, low case volume, and bleeding during procedure. Prevention strategies include the sphincterotomy technique, correction of coagulopathy, and antiplatelet drug prescription. Treatment strategies for post-ERCP bleeding included injection therapy, mechanical tamponade, and thermocoagulation.

Post-ERCP perforation is a rare (less than 1%) but very serious complication. Iatrogenic duodenal perforation can be classified into four types, according to the mechanism. This session dealt with defining the types of perforation, clinical presentation of duodenal perforation, and treatment strategies for each type.23

The incidence of post-ERCP bacteremia varies according to the situation, and usually ranges from 0.5% to 3%. The most common risk factor is incomplete or unsuccessful biliary drainage. This topic included the role of prophylactic antibiotics, guidelines for the prevention of post-ERCP infectious complications, and biliary drainage strategy in patients with hilar cholangiocarcinoma.

Percutaneous transhepatic cholangioscopy (PTCS) allows direct visualization of the bile ducts, and can be used in case of failed ERCP. This session dealt with basic instruments for PTCS (cholangioscope, equipment for electrohydraulic lithotripsy [EHL], and accessories), making fistulous tract and tract dilatation, and techniques for observation of the bile ducts.

PTCS has both diagnostic and therapeutic roles. The indications for diagnostic PTCS are indeterminate biliary strictures, and determination of the longitudinal extent of hilar bile duct tumors. The therapeutic indications are treatment of bile duct stones, treatment of postoperative anastomotic stricture, and local ablation therapy for bile duct cancer, such as photodynamic therapy.

The most common indication for therapeutic PTCS is intrahepatic bile duct stones. This session dealt with the role of PTCS, techniques for making an adequate fistulous tract, methods for stone removal by basket, EHL and laser lithotripsy, and role of PTCS in patients with extrahepatic bile duct stones.

PTCS has both diagnostic and therapeutic roles in patients with bile duct cancer. This session included characteristic images for various types of bile duct cancer, intraductal ultrasonography combined with PTCS, and adequate biopsy methods. The topic of therapeutic PTCS included the role, techniques, and treatment results for PTCS in patients with hilar cancer. Radiofrequency ablation, which is a recently developed technique, was also introduced.

Most gallbladder (GB) polyps are benign cholesterol polyps. However, some polyps that are larger than 1 cm are malignant, and therefore surgery should be considered, given the possibility of GB cancer. Even in polyps that are larger than 1 cm, most resected specimens are benign; unfortunately, it is difficult to distinguish cancerous polyps from benign polyps based on size alone. Focal or segmental GB wall thickening is also a common incidental finding of radiologic abdominal imaging. Common causes of incidental GB wall thickening are adenomyoma or adenomyomatosis, although the possibility of GB cancer should always be kept in mind. In this session, diagnostic strategies for patients with incidental GB polyps and GB wall thickening were introduced, along with interesting cases.

Incidental pancreatic cysts are commonly detected in older patients after routine computed tomography scanning. The natural course of incidental pancreatic cysts is known to be good. However, mucinous pancreatic cysts, such as mucinous cystic neoplasm and intraductal papillary mucinous neoplasm (IPMN), have malignant potential, and thus close follow-up is necessary in cases of indeterminate incidental pancreatic cysts. This session introduced two cases of incidental pancreatic cysts that had progressed to invasive IPMN during follow-up.

Malignant diseases, along with a variety of benign diseases, can cause bile duct stricture and dilatation, and it is occasionally difficult to distinguish benign lesions from malignancies based on imaging alone. In cases of bile duct dilatation without stricture, the benign condition is more common than malignant disease. This session introduced etiologies of bile duct dilatation and endoscopic evaluation strategies, such as EUS and ERCP.

As the number of gastroscopy evaluations increase, incidental AOV lesions, such as prominent AOV, are frequently detected. Thus, it is important to differentiate AOV tumors from other benign conditions. This session introduced endoscopic evaluation methods for AOV, typical endoscopic images for each AOV disease, and several cases of prominent AOV lesions.

In recent years, many new antiplatelet and anticoagulant drugs have been introduced, including new adenosine diphosphate antagonists, such as prasugrel, ticagrelor, and cangrelor, and new anticoagulants, such as dabigatran, rivaroxaban, and apixaban. Endoscopists should be aware of the characteristics of these new drugs, in order to minimize procedural complications that may occur in patients currently receiving these drugs.

When deciding how to manage antithrombotics during endoscopic procedures, the risk of bleeding and thromboembolic events during the procedure must be weighed. In order to achieve successful endoscopy in patients taking antithrombotics, it is also important that physicians from three departments (neurology, cardiology, and gastroenterology) are all familiar with the pharmacologic actions of these drugs, and provide multidisciplinary care for the patients. Oh24 stressed two common mistakes that endoscopists make during endoscopy in patients taking antithrombotics. One common mistake is asking patients to stop taking aspirin without assessment of underlying disease, and the other is not informing patients when they should restart their medication.

Existing guidelines are valuable, but should not be a substitute for a careful, personalized risk assessment strategy that involves both patient and physician. There are several useful guidelines for endoscopy in patients with antithrombotic therapy.25,26,27