Various studies by Japanese endoscopists have demonstrated that colorectal endoscopic submucosal dissection (ESD) can overcome technical limitations of the endoscopic mucosal resection (EMR) technique such as piecemeal resection for flat lesions larger than 20 mm, resection of lesions involving the dentate line or the ileocecal valve and lesions with the non-lifting sign, and achieve higher en bloc resection rate. However, it is infrequently performed in Western countries in comparison with Japan, despite the advantages explained above. There are some differences between Japan and Western countries in environments and clinical settings for performing ESD in the colorectum. Endoscopists who perform colorectal ESD around the world are considering that refinements in ESD techniques, devices and training will be necessary to further reduce a higher risk of complications and longer procedure times before adoption of ESD can be recommended on a widespread international scale.
Endoscopic mucosal resection (EMR) is widely accepted for precancerous lesions such as colorectal (CR) adenoma and dysplasia in Barrett's esophagus, and in general for early stage gastrointestinal (GI) cancers with a low risk of lymph node metastasis. CR-EMR has, however, several limitations such as piecemeal resection for flat lesions larger than 20 mm, resection of lesions involving the dentate line or the ileocecal valve and lesions with a non-lifting sign. Piecemeal resection results in less accurate histological assessment and leads to an increase in local recurrence.
Endoscopic submucosal dissection (ESD) was developed in Japan to resect early stage GI tumors en bloc including large lesions and positive non-lifting sign lesions.1–9 ESD has been a significant advance in therapeutic endoscopy with its major advantage being the ability to achieve a higher en bloc resection rate due to submucosal dissection with a direct view using a special electrosurgical knife. This results in enhanced curability and more accurate histopathological assessment.
Various studies by Japanese endoscopists have demonstrated that CR-ESD can overcome technical limitations of EMR and achieve higher en bloc resection rate. However, this procedure is known to have several disadvantages such as greater technical difficulty, longer procedure time and increased risk of related complications including perforation and bleeding compared to conventional EMR. In contrast, it is infrequently performed in Western countries compared to Japan, regardless of the advantages explained above.10–12
This review focuses on the differences in environments and clinical settings for performing ESD in the colorectum between Japan and Western countries, according to experiences and perspectives of highly experienced endoscopists from Japan and Europe, and to related published work.
COLONOSCOPY TECHNIQUE AND EQUIPMENT
It has been suggested that a difference in colonic anatomy between Western and Asian patients may result in a more difficult colonoscopy in the former. According to the measurement of colonic length of Asian and Caucasian patients, the colonic length of Caucasian patients was significantly longer. In addition, Caucasian patients have a higher incidence of sigmoid colon adhesions and increased colonic mobility when compared to Asian.13 In the clinical setting, short-type (1.3 m) colonoscopes are regularly used in Japan, whereas in most Western countries long (1.7 m) colonoscopes are used. Therefore, a more difficult colonic anatomy and the frequent need for longer colonoscopes would support the possibility that colonoscopy and related therapeutic procedures are more complex in Western patients.
Because easier handling and maneuverability of the endoscope is required when performing this procedure, using a shorter length and thinner diameter colonoscope is recommended, resulting in a more direct approach to the targeted area, compared to a standard colonoscope. A new type of colonoscope (PCF-Q260J; Olympus, Tokyo, Japan) is available,7 specially designed for performing ESD, with the following features: (i) thinner diameter (10.5 mm); (ii) increased bending angle; and (iii) shorter length of the stiff portion at the front of the colonoscope. A shorter pediatric colonoscope (PCF-Q260AZI; Olympus) with variable stiffness is also recommended. Both colonoscopes also have an irrigation water-jet feature for better visualization of the cutting line and bleeding points during submucosal dissection. We also prefer to use a gastroscope with an irrigation water-jet feature in rectal cases and double balloon colonoscope for cases in which it is difficult to control the colonoscope. Using a gastroscope results in better handling and maneuverability and easier endoscope retroflex positioning in the colorectum. The use of the balloon function stabilizes control of the colonoscope, even in difficult cases.
The quality of bowel preparation is crucial for the detection of colonic polyps, especially of the flat type. In Japan, the standard method for bowel preparation is polyethylene glycol electrolyte solution, which is administrated 2–3 h before the time of colonoscopy. Moreover, whenever possible, the process of bowel cleansing takes place in the endoscopy unit, where the patient drinks the bowel preparation agent. The quality of bowel preparation probably strongly influences the practice of CR-ESD at different levels. First, the detection of flat-type lesions (especially laterally spreading tumor of non-granular type [LST-NG] and depressed IIc type) is very challenging, and an excellent quality of cleansing is required. Second, LST-NG are the main indication for ESD in Japan;14 however, they are said to be rare in Western countries (probably, under-detection is one of the reasons why they are an infrequent finding).15 Third, an excellent quality of cleansing is mandatory to perform CR-ESD. Moreover, in cases where perforation takes place, an excellent quality of cleansing may facilitate the adequacy of endoscopic treatment as a definitive solution, instead of surgery.16
Although there is enough evidence supporting the superior efficacy of bowel preparation when the agent has been administrated, at least in part, a few hours before colonoscopy (which is the method universally used in Japan), this is still not the common practice in many Western endoscopy units.17,18
Submucosal injection solution for ESD
An ESD procedure requires a longer-lasting solution to facilitate identification of the cutting line during dissection of the submucosal layer and reduction of the risk of perforation in the narrow angulated and thinner wall of the colorectum.19 Normal saline (NS) solution has been commonly used for endoscopic resection around the world, but it does not provide a proper submucosal fluid cushion nor maintain the desired height, because of the rapid diffusion of NS into the surrounding tissue.
Glycerol and sodium hyaluronic acid (SHA) solutions are generally used for CR-ESD in Japan.6,20 Glycerol is a hypertonic solution consisting of 10% glycerin and 5% fructose in an NS solution that has been used i.v. to treat cerebral edema with no toxic systemic effects.21 SHA has a high viscosity and water retention capability without being antigenic or toxic to humans and has provided the longest-lasting fluid cushion.4,22 A higher successful en bloc resection rate and lower perforation complication rates have been reported using SHA, particularly for CR-ESD. However, neither solutions are available nor approved for commercial use as submucosal solutions in the USA.
Hydroxypropyl methylcellulose (HPMC) demonstrated long-lasting submucosal fluid cushion with minimal tissue reaction in clinical studies.23 In fact, CR-ESD using HPMC was reported from an institution in the USA.24 Therefore, facilitative submucosal injection solutions having a similar effect to glycerol and SHA are needed and can be available in Western countries as well.
Sedation during ESD
Western endoscopists prefer to use propofol for sedation during colonoscopy in terms of satisfying certain criteria.25 Propofol sedation has also been identified as a factor independently associated with some quality markers of colonoscopy, including cecal intubation and polyp detection rates.26 In contrast, the safety and usefulness of consciousness or unsedated colonoscopy has been reported not only from Japan but also from Western countries recently, because studies from Western countries suggest that cecal intubation rates are not adversely affected by performing the examination unsedated, in addition to some advantages including cost–benefit and lower complication rates.27
If the position of the patient is not going to be changed during colonoscopy, then stronger sedation can be used. However, taking advantage of gravitation during colonoscopy is useful, as the submucosal dissection plane can be observed more clearly in certain patient positions, in which the partially dissected lesion is pulled down by its own weight. This results in safer cutting and better visualization of the cutting line, further facilitated by the stagnant water being mobilized in certain patient positions, due to migration of water retention in the lumen. Patient rotation can be used during CR-ESD by Japanese endoscopists because they do not apply deep sedation to their patients.
ESD TRAINING AND EXPERIENCE
It should be noted that successful endoscopy procedures depend, in a large part, on the skillful use of appropriate endoscopic techniques and devices. Although CR-ESD is still only anecdotally performed in Western countries, the number of publications on colorectal ESD from Western countries has been increasing (based on literature searches using PubMed).
Training and clinical experience, of course, are necessary to achieve a satisfactory level of skill for performing ESD.7 One of the main limitations to the implementation of ESD in Western countries is that, as compared to Japan, there are very few institutions with enough expertise in CR-ESD to become training centers. However, in Japan, a significant number of endoscopists have experience, at a minimum, in over 50 CR-ESD cases.6 Training in animal models can help endoscopists overcome the learning curve before starting ESD in humans.12,28,29 In order to assist endoscopists in acquiring the necessary CR-ESD skills more efficiently, the development of a simulation system involving an ESD training model such as the stomach of a pig is important. In Japan, separate ESD training models are available for esophageal, gastric and CR-ESD (Fig 1; Johnson & Johnson Medical, Tokyo, Japan). Blood flow using red ink also can be provided in the porcine gastric and bovine models to experience bleeding during ESD.
Performing ESD in a clinical setting with appropriate professional guidance and supervision also is an important consideration in terms of the learning curve, at least in the early phases of actual clinical experience.
In summary, there are some differences between Japan and Western countries in environment and clinical settings, including colonic anatomy, endoscopic equipment, related devices and ESD training systems for performing CR-ESD. Endoscopists who perform colorectal ESD around the world are, however, considering that refinements in ESD techniques, devices and training will be necessary to further reduce the associated negative factors, including a higher risk of complications and longer procedure times, before the adoption of ESD can be recommended on a widespread international scale.
The authors are grateful to Deirdre D'Arcy for proof-reading the manuscript.