No abstract

Colorectal endoscopic submucosal dissection (ESD) has become common in recent years. Suitable lesions for endoscopic treatment include not only early colorectal carcinomas but also many types of precarcinomatous adenomas. It is important to establish practical guidelines in which the preoperative diagnosis of colorectal neoplasia and the selection of endoscopic treatment procedures are properly outlined, and to ensure that the actual endoscopic treatment is useful and safe in general hospitals when carried out in accordance with the guidelines. In cooperation with the Japanese Society for Cancer of the Colon and Rectum, the Japanese Society of Coloproctology, and the Japanese Society of Gastroenterology, the Japan Gastroenterological Endoscopy Society has recently compiled a set of colorectal ESD/endoscopic mucosal resection (EMR) guidelines using evidence-based methods. The guidelines focus on the diagnostic and therapeutic strategies and caveat before, during, and after ESD/EMR and, in this regard, exclude the specific procedures, types and proper use of instruments, devices, and drugs. Although eight areas, ranging from indication to pathology, were originally planned for inclusion in these guidelines, evidence was scarce in each area. Therefore, grades of recommendation were determined largely through expert consensus in these areas.

Many clinical studies on narrow-band imaging (NBI) magnifying endoscopy classifications advocated so far in Japan (Sano, Hiroshima, Showa, and Jikei classifications) have reported the usefulness of NBI magnifying endoscopy for qualitative and quantitative diagnosis of colorectal lesions. However, discussions at professional meetings have raised issues such as: (i) the presence of multiple terms for the same or similar findings; (ii) the necessity of including surface patterns in magnifying endoscopic classifications; and (iii) differences in the NBI findings in elevated and superficial lesions. To resolve these problems, the Japan NBI Expert Team (JNET) was constituted with the aim of establishing a universal NBI magnifying endoscopic classification for colorectal tumors (JNET classification) in 2011. Consensus was reached on this classification using the modified Delphi method, and this classification was proposed in June 2014. The JNET classification consists of four categories of vessel and surface pattern (i.e. Types 1, 2A, 2B, and 3). Types 1, 2A, 2B, and 3 are correlated with the histopathological findings of hyperplastic polyp/sessile serrated polyp (SSP), low-grade intramucosal neoplasia, high-grade intramucosal neoplasia/shallow submucosal invasive cancer, and deep submucosal invasive cancer, respectively.

Nonpolypoid colorectal neoplasms are grossly classified into three groups: slightly elevated (small flat adenomas), laterally spreading, and depressed. Flat adenomas are not invasive until they are rather large, whereas depressed lesions can invade the submucosa even when they are extremely small. Nonpolypoid lesions are difficult to detect and are often overlooked. Keys to detect them are their slight color change, interruption of the capillary network pattern, slight deformation of the colonic wall, spontaneously bleeding spots, shape change of the lesion with insufflation and deflation of air, and interruption of the innominate grooves. Spraying of indigo carmine dye helps to clarify the lesions. A pit pattern analysis with a zoom colonoscope is useful for the diagnosis and staging of early colorectal cancer. Small flat adenomas are thought to be precursors of protruded polyps and lateral spreading tumors, whereas depressed lesions are thought to grow endophytically and become advanced cancers. Small depressed lesions are treated with an endoscopic mucosal resection (EMR) technique; but when they massively invade the submucosa, surgical resection is indicated. Laterally spreading tumors are not as invasive despite their large size and therefore are good indications for the EMR or piecemeal EMR method. Small flat adenomas need not be treated urgently, as almost none is invasive. Accurate diagnosis with dye-spraying and zoom colonoscopy is vital for deciding the treatment strategy.

Suitable lesions for endoscopic treatment include not only early colorectal carcinomas but also several types of precarcinomatous adenomas. It is important to establish practical guidelines wherein preoperative diagnosis of colorectal neoplasia and selection of endoscopic treatment procedures are appropriately outlined and to ensure that actual endoscopic treatment is useful and safe in general hospitals when carried out in accordance with guidelines. In cooperation with the Japanese Society for Cancer of the Colon and Rectum, the Japanese Society of Coloproctology, and the Japanese Society of Gastroenterology, the Japan Gastroenterological Endoscopy Society compiled colorectal endoscopic submucosal dissection/endoscopic mucosal resection guidelines by using evidence‐based methods in 2014. The first edition of these guidelines was published 5 years ago. Accordingly, we have published the second edition of these guidelines based on recent new knowledge and evidence.