Dig Dis Sci (2014) 59:2081–2090 DOI 10.1007/s10620-014-3308-y
REVIEW
Training Methods and Models for Colonoscopic Insertion, Endoscopic Mucosal Resection, and Endoscopic Submucosal Dissection Naohisa Yoshida • Nilesh Fernandopulle • Yutaka Inada • Yuji Naito • Yoshito Itoh
Received: 6 May 2014 / Accepted: 17 July 2014 / Published online: 8 August 2014 Ó Springer Science+Business Media New York 2014
Abstract Colonoscopic examination is considered an effective examination for the detection of colorectal cancers. Additionally, early colorectal cancers can be resected using endoscopic techniques such as endoscopic mucosal resection and endoscopic submucosal dissection. However, those examinations and treatments need special techniques. Various training methods are practiced to acquire such endoscopic techniques throughout the world. In clinical cases, magnetic positioning devices help endoscopic insertion by less experienced endoscopists. There is a physical model made by polyvinyl chloride and a virtual simulator for training of colonoscopic insertion. Various techniques including a method to apply pressure to the abdomen and consideration for patient’s pain can be trained using these models. In view of extensive training of endoscopic mucosal resection and endoscopic submucosal dissection, animal models are useful and actually used. Live animal models of minipig, which entails blood flow, are ideal and used frequently, but are cumbersome to prepare. On the other hand, ex vivo animal models using intestine of porcine and bovine are convenient for preparation and less expensive. Unique ex vivo animal models with blood flow have been developed recently and techniques for hemostasis can be practiced. With respect to a method of training for colorectal endoscopic submucosal dissection, a stepwise system has been adopted throughout the world. Thus, first they observe the expert’s technique,
N. Yoshida (&) N. Fernandopulle Y. Inada Y. Naito Y. Itoh Department of Molecular Gastroenterology and Hepatology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan e-mail:
[email protected]
then practice training of animal models, and finally, they perform clinical rectal cases. The system is useful for a safe and definite procedure. In this review, we reveal various training methods for colonoscopic examinations and treatments. Keywords Endoscopic submucosal dissection Animal model Endscopic mucosal resection Training Insertion
Introduction Colorectal cancer (CRC) is a common gastrointestinal malignancy in the United States, Europe and Japan [1]. Actually, the incidence of CRC in Japanese males is increasing and is approximately 40 in 100,000 men recently. This value is similar to the rate of CRC in developed Western countries such as the United States, Australia, and Spain [1]. Most CRCs are thought to arise from preexisting adenomas based on the concept of the adenoma-carcinoma sequence. Adenomas and early CRCs must be diagnosed carefully by endoscopic examination, including chromoendoscopy and equipment imagedenhanced endoscopy techniques such as narrow band imaging and flexible spectral imaging color enhancement [2–4]. Improvements in endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have facilitated removal of large, early colorectal cancers [5–8]. Considering that the number of early CRCs will increase in parallel to CRC screening, enhanced demands to treat early CRC with optimal minimal invasive endoscopic techniques will be a challenge in the West and Japan. For less experienced endoscopists, various training methods such as use of physical models, virtual simulators and animal models and clinical stepwise practice are performed to acquire
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such endoscopic techniques. In this paper, we reviewed those training methods for each endoscopic procedure.
Training Method for Insertion of Colonoscope Normally, training for insertion of colonoscopy entails initially watching experts performing insertion, then withdrawing the colonoscope with expert supervision, and finally, performing colonoscopy with help of an expert’s navigation. Knowing an endoscope’s location during insertion is one of the most important things. The cecum is a valuable indicator of performance at all levels of colonoscopic expertise. Hepatic and splenic flexure are also important land marks to know endoscope position in almost all cases. All trainers examine it critically on a regular basis and teach it to trainees. However, it still remains a technically demanding procedure, and is both difficult to learn and time consuming to teach [9]. One reason is that the colonoscopic formation inside the patient, especially during looping, is hard to be understood by less experienced endoscopists. In clinical cases, X-ray helps as a guide for less experienced endoscopist (Fig. 1a). However, X-ray has a risk of radiation exposure. On the other hand, magnetic navigation devices give the endoscopist the ability to see the three-dimensional configuration of the whole instrument and the exact location of its tip within the abdomen (Fig. 1b, c) [10]. The magnetic navigation device is reported to significantly improve performance of colonoscopy, particularly when used by less experienced endoscopists, or by experts in technically difficult cases;
Fig. 1 Training methods and models for colonoscopic insertion. a Xray. b Magnetic navigation devices. c Looping view of magnetic devices. d Physical model (Colonoscopy model Type I–B, Koken). e Physical model (Colon model CM-15, Kyoto Kagaku). f Imaginary
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loops are straightened or controlled effectively, resulting in quick intubation times and high completion rates [11]. Additionally, abdominal hand pressure is more effective when the endoscopist and endoscopy assistant could see the magnetic image view. However, the attainment of basic competence includes risks to patients’ safety and comfort even if X-ray and magnetic images are used. Thus, various simulation models such as physical models and virtual models are performed throughout the world. There are two physical models (Colon model CM-15, Kyoto kagaku, Kyoto, Japan; Colonoscopy model Type I–B, Koken Co. Tokyo, Japan) made by polyvinyl chloride for the training of insertion of colonoscopy (Fig. 1c, d) [12]. They are designed for use in conjunction with regular colonoscopic equipment. Techniques such as hooking the fold, forming loops and unlooping can be trained using a real colonoscope. Additionally, location of the tip of the colonoscope and colonoscopic formation can be understood easily. Appropriate hand pressure of abdomen for insertion is also trained by use of this model. In the model (CM-15), they can experience diverse cases changing the setting. Additionally, imaginary lesions can be made using ink in this model and appropriate observation is practiced in our institution (Fig. 1e). Controlled manipulation of the endoscope such as twisting, pushing and pulling of the endoscope in observation and endoscopic treatments is also practiced. However, there is a lack of evidence in the efficacy of these physical models. Further studies should be performed to examine the efficacy of these physical models. There is another type of simulator such as computerbased virtual ones (AccuTouch System, Immersion
lesion by violet ink in the physical model (CM-15). g Virtual simulator (the GI Mentor II, Simbionix Corp.). h Endoscopic view of the virtual simulator (the GI Mentor II, Simbionix Corp.)
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Fig. 2 Training model for EMR. a Harvested porcine cecum. Imaginary lesion with violet ink. b Mucosal elevation by 0.13 % hyaluronic acid and snaring. c Resection. d Polypectomy in virtual simulator (the GI Mentor II, Simbionix Corp.)
Medical, USA; the GI Mentor II, Simbionix Corp., USA). These simulators include their own monitors and modified colonoscopies (Fig. 1g, h). They can experience diverse cases changing settings of both virtual simulators. There are lots of reports about the efficacy of virtual simulators [13–16]. Only virtual simulators have functions to learn patients’ discomfort. However, Hill et al. [12] reported that physical models had better evaluation in a physical arrangement, haptic response, and looping than virtual simulators. Additionally, physical models are less expensive than virtual simulators though physical models need clinical colonoscopic equipment. A recent systemic review for a virtual simulator reported that there were no differences in total procedure time for colonoscopy between the simulator group and no simulator group [17]. Thus, the effectiveness of these simulations is considered to be restricted to the early part of the learning curve [12]. Overall, which models and simulators are appropriate for trainees should be considered according to trainee’s skill levels and their specific educational purposes.
Training for EMR Endoscopic mucosal resection is generally performed for early CRCs worldwide. The saline injection-assisted method was first described by Rosenberg, who identified it as a safety factor for the removal of rectal and sigmoid
polyps, and was reintroduced by Tada et al. in 1984 [18– 20]. Most adenomas and intramucosal cancers can be resected by EMR. The high rate of en bloc resection in EMR for colorectal polyps less than 20 mm in size is achieved and piecemeal EMR enables us to remove large colorectal tumors more than 20 mm in size. However, it has a high rate of local recurrence (7.9–21.4 %) [21–26]. Normally, training of EMR for colorectal polyps first involves observing experts’ technique, then performing easy cases such as small polyp in the rectum with supervision of an expert, and finally, going through difficult lesions. In clinical practice, the use of 0.13 % hyaluronic acid (HA) (Mucoup, Johnson & Johnson Co. Tokyo, Japan; Seikagaku Co. Tokyo, Japan) in EMR is recommended for less experienced endoscopists. The EMR procedure time of less experienced endoscopists is longer than that of the veteran endoscopists. The elevation achieved by the injection solution such as normal saline decreases according to the procedural time [27]. HA can maintain higher and longer mucosal elevation than normal saline [27, 28]. Our study proved that 0.13 % HA was associated with better complete resection rates by less experienced endoscopists [29]. Additionally, we suggest that less experienced endoscopists should use 0.13 % HA in EMR to prevent perforation, which can be caused by low mucosal elevation. In Japan, harvested animal models have been used for training of EMR recently. Imaginary lesions are made using red and violet ink in the harvested models.
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Thereafter, injection and snaring can be practiced repeatedly (Fig. 2a–c). Especially, how to determine the recommended locus of injection according to each lesion is well trained. Additionally, how to control poor manipulation during the procedure and do snaring in a difficult situation are also practiced using animal models. However, there is a lack of evidence in the efficacy of animal model training. On the other hand, there are no virtual simulators for training of EMR. Only polypectomy to pedunculated polyps are practiced using the virtual simulator described above (the GI Mentor II, Simbionix Corp.) (Fig. 2d).
Stepwise Training for ESD Throughout the World Endoscopic submucosal dissection is useful for resecting colorectal tumors more than 20 mm in size en bloc. The first description of ESD from Japan was in the early 1990s and the first English description of an ESD was a few years later by Gotoda et al. [30]. Although the technique of an ESD extended to the whole of Japan and other Asian countries, it has not been widely accepted in the West [31– 40]. It was only in 2007 that Repici et al. [41] reported the first series of cases involving 29 patients with large lesions that were treated by circumferential incision using an insulation-tip knife followed by snare resection. Several reasons have been postulated for the skepticism in adopting this challenging technique. A perforation is one of the problems in colorectal ESD and the rate is reported to be higher than that for EMR [35]. Appropriate training, a safe strategy, and adoption of suitable accessories are necessary to perform ESD and prevent the associated complications, including perforation, during ESD. In Japan, colorectal ESD training is a stepwise system starting with observing and assisting in ESD procedures performed by experts [42–44] (Fig. 3). Next, animal model training is performed to the best extent possible. Finally, clinical practice is performed under the supervision of
Fig. 3 Stepwise training for colorectal ESD
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experts. We believe that experience obtained by training on an animal model would also improve performance of clinical colorectal ESD. Generally, clinical practice training proceeds according to the difficulty of the procedure, beginning with gastric ESD, then rectal ESD, and finally colonic ESD. The importance of experience was shown by studies that reported a beginner must perform about 20–40 gastric ESD procedures to gain early proficiency [45, 46]. Ohata et al. [44] reported that trainees with little experience in gastric ESD (i.e. 30 cases), require an average of 30 cases of colorectal ESD to reach a stable level of technical competency. Hotta et al. [47] also showed that approximately 40 procedures were sufficient to acquire skill in avoiding perforations, and the perforation rate in the first 40 cases was about 12.5 %. With respect to endoscopic knives, there are lots of kinds of knives available for colorectal ESD [35]. Scissor type knives such as the Clutch cutter (Fujifilm co., Tokyo, Japan) or SB knife (Sumitomo Bakelite, Tokyo, Japan) is easy to operate and is recommended for less experienced endoscopists especially in difficult situations [48, 49]. It can grasp the tissue and then it is applied an electrical current. These devices prevent perforation by unintentional movement. On the other hand, with respect to techniques, EMR with circumferential incision is recommended for less experienced endoscopists before complete ESD (Fig. 4a–d). This method is called a simplified ESD in some reports [38]. The procedure of this method was reported to be shorter and easier than complete ESD. In the West, Iacopini et al. [50] describe a similar stepwise training for ESD. Compared to Japanese training, they revealed the necessity of Japanese expert observations in the stepwise training. Probst et al. [51] clearly demonstrated the existence of a learning curve and the fact that colorectal ESD could be successfully performed by skilled Western endoscopists who had received some degree of training with Japanese specialists in the field. Generally, the most important step during the initial stages of ESD would be careful lesion selection, with cases limited to smaller lesions in the stomach or rectum. In contrast to Japan, the rectum and not the stomach is suggested as the initial target organ for training in patients. The main reason given for this is the higher rectal tumors found in the West and not that the latter is easier [52]. And a rectal case is recommended first because the rectal ESD is easier to be completed than colonic ESD. The rectal ESD learning curve was reported to demonstrate the feasibility and safety of the procedure with a competence threshold set at 20 procedures [50]. In contrast, the colonic ESD learning curve showed extremely low en bloc resection rates and a high perforation risk in the early phase, although competence was steeply achieved after 20 procedures. They also suggested comparing the 20 rectal ESDs competency threshold with those ranging from 30 to 50 procedures
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Fig. 4 EMR with circumferential incision. a Superficial lesion 14 mm in diameter on the sigmoid colon. b Mucosal elevation was achieved after injection. However, the center of the tumor was not
elevated enough. c Circumferential mucosal incision was performed for superficial tumor. d En bloc resection was achieved by snaring. The procedure time of this method was only 10 min
identified in learning curves calculated based on gastric lesions in Japan. On the other hand, in the United States, Draganov et al. [53] reported a similar stepwise training preceded by experience in diagnostic and advanced therapeutic procedures, especially with conventional EMR. He also emphasized that training on ex vivo models at handson training courses, especially ones provided by the American Society of Gastrointestinal Endoscopy (ASGE), is recommended. The importance of observing Japanese experts is further reiterated in his schedule. Additionally, the ASGE Institute for Training and Technology (IT&T) was established in Chicago for a world-class endoscopic education and training, and the training for ESD has been performed recently. With respect to a workshop which entails experimental ESD instructional training using in vivo or ex vivo pigs under the supervision of Japanese and Western experts, workshops have been created to allow exposure to ESD techniques. However, the limited number of dissections performed at these workshops does not allow an endoscopist to be proficient and comfortable with this procedure before use on patients. Additionally, not every endoscopist can attend these workshops due to time, travel, and cost limitations. Hence the impact of these methods on
ESD performance has yet to be determined [54]. Berr et al. [55] describes a workshop where each endoscopist only did an average of 4.1 dissections with a 22 % perforation rate and concluded that intense training is necessary to reduce the risk of perforation. There are courses that demonstrate endoscopic techniques in real time, termed live demonstrations. In live demonstrations, less experienced endoscopists have opportunities to watch real expert’s operations. Those are one of most important ways to achieve the technique of colorectal ESD. However, they must be conducted with the patient as first priority according to a guideline from ASGE [56]. With respect to trainers in a workshops and a live seminar, it is important that all trainers should at least have attended a ‘‘Train the Trainers’’ course and, better still, should have achieved some form of educational qualification.
Usefulness of Animal Model for Training of Colorectal ESD With respect to training of animal models, both in vivo animal models and ex vivo animal models using harvested
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Fig. 5 In vivo animal model of porcine rectum. a A marking as an imaginary lesion was performed. b A circumferential mucosal incision and a partial dissection was performed. c En bloc resection was achieved
organs have been used [57–59]. Porcine and canine in vivo models have been reported to be useful systems for ESD training [57, 59] (Fig. 5). In vivo animal models which have blood flow are ideal for training and frequently used throughout the world. However, in vivo animal models are expensive and inconvenient. Additionally, they require that the animal is sacrificed afterward. In contrast, ex vivo animal models are inexpensive and convenient. Hon et al. [59] demonstrated the usefulness of a porcine colon ex vivo animal model for training in colorectal ESD. However, one of the weaknesses of ex vivo animal models is the lack of blood flow. Prevention of perioperative hemorrhage and rapid hemostasis are one of the most important techniques in clinical ESD. Recently, an ex vivo animal model with blood flow has been developed by Johnson & Johnson with many Japanese endoscopists’ help, and this has enabled more practical training including endoscopic hemostasis [42].This model has been used in an academic seminar for training of colorectal ESD to less experienced endoscopists in Japan. According to a survey of 25 Japanese and three Western experts, specialized training with animal models is strongly recommended before attempting colorectal ESD [60]. In the West, ex vivo models using gastric remnants from patients undergoing sleeve gastrectomy have been used for ESD training [61]. According to the report, training using this model has improved dissection times from approximately 2 h to 30 min for a 2-cm simulated lesion. Parra-Blanco et al. [58] reported 30 animal model ESDs carried out on pig models, eight ex vivo models (two in esophagus, six in stomach) in six harvested organs and 22 in the in vivo model. In the study, he proposed a strategy for training in ESD in the absence of experts to supervise the procedures and ensure the patients’ safety, although it must be mentioned the author received ESD training as an observer and on animal models in Japan. About the period of animal models, a minimum of 30 ESDs was suggested by the European Society of Gastrointestinal Endoscopy, but 10–15 cases were suggested to be sufficient for significant technical improvement [52].
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With respect to characteristics and preparation of ex vivo animal models, there is a special model for training of gastric ESD model (Olympus Co., Tokyo, Japan) (Fig. 6a, b). There are lots of holes in this model. Harvested porcine stomach is attached to the hole. On the other hand, harvested porcine cecum, rectum, bovine cecum and rectum are used as animal models for colorectal ESD and they can be obtained from fresh meat markets for use. In a preparation for training in colorectal ESD, an endoscopic overtube (TOP, Tokyo, Japan) is attached to one end of the organ for insertion of the endoscope (Fig. 6c). For organs other than the cecum, the other end is ligated. To mimic the abdomen, the cecum and rectum are fixed to a square board. The patient plate electrode is attached below the organs. To mimic blood flow, red ink is used. The artery around the bovine cecum is detached (Fig. 6d). A plastic needle is inserted into the artery and a syringe containing red ink is connected. The red ink is injected until the mucosal vasculature can be visualized by endoscopy (Fig. 6e, f). Thereafter, red ink is maintained by intermittent injection during ESD and the vessels in the submucosa can be seen (Fig. 6g). Various ex vivo animal models such as bovine cecum, rectum, porcine cecum, rectum, and stomach had each characteristic features, making it possible to choose a suitable animal model according to the skill level of the endoscopist (Table 1) [42]. Based on various features, we recommend the porcine and bovine rectum for training of beginners in colorectal ESD. Regularly, imaginary lesion is made by coagulation of tips of ESD knifes, but a more realistic imaginary lesion can be made by sponge (Fig. 6h). Moreover, thick vessels can be transplanted in the submucosa with special technique for preventing severe hemorrhage (Fig. 6i). The training for hemostasis can be performed with this model. However, there is a limitation with the animal model such that the benefit of training is assessed only in the animal model. There are several differences between the harvested animal model and the human colorectum that could produce different results. Further studies should be performed to
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Fig. 6 Preparation of the ex vivo animal model. a Gastric ESD model with holes. b Training of ESD using porcine stomach. c The ex vivo animal model with blood flow was made using bovine cecum. An endoscopic overtube was attached to one end of the organ for insertion of the endoscope. A tube with red ink was connected to the model. d The artery around the bovine cecum was detached. A plastic
Table 1 Characteristics of various harvested animal models
needle was inserted into the artery. e Regular ex vivo animal model of the bovine cecum without blood flow. f Original ex vivo animal model of the bovine cecum with blood flow. g The Porcine rectum. A vessel was seen in submucosa. h The Porcine rectum. Imaginary lesion made by sponge. i The Porcine rectum. A thick vessel was transplanted in the submucosa
Model
Mucosal injection
Submucosal elevation
Muscle layer
Making models with blood flow
Practice for EMR and ESD
Rectum porcine
Middle
High
MiddleTight
Easy
For colonic ESD
Cecum porcine
Difficult
Middle
Tight
Middle
For EMR
Stomach porcine
Difficult
High
Tight
Easy
For gastric ESD
Cecum bovine
Easy
Middle
Coarse
Easy
For EMR
Rectum bovine
Easy
High
Middle
Difficult
For EMR and colonic ESD
examine the efficacy of these animal models. On the other hand, there are no virtual simulators for training of ESD. The development of a virtual simulator for EMR and ESD is expected. With respect to training for complication, the perforation rates during ESD and EMR do not decrease to zero even if the skill level improved greatly. Therefore, we
believe that the endoscopist must also obtain expertise in endoscopic closure. Small perforations can be closed by endoscopic clipping [62]. However, endoscopic clipping requires a high level of endoscopic skill and experience, and perforation is relatively rare in clinical medicine, making it difficult to gain experience in the endoscopic clipping technique in clinical practice. Training of
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Fig. 7 Ex vivo animal model with perforation for training of endoscopic closure. a After EMR, the endoscopic knife was used to make a 2-mm hole in the proper muscle layer of the ulceration. b The endoscopic closure of the hole was performed with four endoscopic clips
endoscopic clipping for perforation can be practiced with ex vivo animal models. After EMR or ESD, the endoscopic knife was used to make a 2–3-mm hole in the proper muscle layer of the ulceration (Fig. 7a). The perforation was confirmed as a small hole on the outside of the model. The endoscopic closure of the hole was performed with endoscopic clips (Fig. 7b). The completion of endoscopic closure was confirmed by cessation of air leaking out of the models. Our previous study showed that repeated endoscopic closure improved the non-experts’ completion rates and decreased their procedure times [42].
Conclusion Physical models and virtual simulators are used for insertion of a colonoscope. For EMR and ESD, in vivo and ex vivo animal models are adopted. There are pros and cons for each training model. Trainers and trainees have to choose a suitable model to match their needs. Finally, systematic stepwise training, training models, improved accessories, workshops, and live demonstrations enable standardization of colonoscopic techniques. Acknowledgments We thank Yasuhisa Abe and Shigenori Shikata for providing ex vivo animal models. We also thank Ryohei Hirose, Kiyoshi Ogiso, Yasutaka Morimoto, Ken Inoue, Daisuke Hasegawa, Naoki Wakabayashi and all other members at the Department of Molecular Gastroenterology and Hepatology in Kyoto Prefectural University of Medicine for several studies related with this review. Conflict of interest Yoshito Itoh is affiliated with AstraZeneca Co., Ltd., Eisai Co., Ltd., Otsuka Pharmaceutical Co., Ltd., MSD K.K., Dainippon Sumitomo Pharma Co., Ltd., Chugai Pharmaceutical Co., Ltd., FUJIFILM Medical Co., Ltd. and Merck Serono Co., Ltd. Yoshito Itoh received research grants from MSD K.K. and BristolMyers K.K. Yuji Naito received research grants from Otsuka Pharmaceutical Co., Ltd. and Takeda Pharmaceutical Co., Ltd. The other authors have no conflicts of interest to declare. Besides, these things
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described above, there are no financial supports or relationships that may pose conflict of interest in our manuscript.
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