Distal Cap-Assisted Endoscopic Mucosal Resection (EMR-DC) For Non-lifting Colorectal Polyps – Are We Doing It Right?

Endoscopic mucosal resection (EMR) has evolved to become the widely adopted technique for managing intermediate and large non-pedunculated colorectal neoplasia. Several methods of EMR have been described in the literature. Broadly, the techniques can be classified into those that are performed with submucosal injection and those with suction alone [1]. The critical part of EMR is to resect the affected mucosa and submucosa while avoiding injuring the muscularis propria. The simplest and easiest way to prevent entrapping the muscularis propria is to inject fluid into the submucosal layer to expand it. Adequate expansion of the submucosa allows for a safe margin for resection of the diseased mucosa. By adopting the inject-lift-and-cut technique, EMR can be performed safely in any part of the gastrointestinal tract [2].

“Endoscopists need to know how to analyze and interpret the endoscopic features of lesions, understand the risk of lymph node metastasis, carefully select patients and consider their preferences, follow the accepted indication, and adopt standardized resection techniques”

In clinical practice, there is a considerable variation in the technique of EMR as evidenced by a higher reported rate of incomplete resection and recurrence (15–30 %) following EMR of large colonic polyps [3]. Subsequent endoscopic removal of such lesions can be challenging because of extensive scarring and fibrosis underneath the lesion, increasing the risk of complications. Also, in addition to mastering the EMR technique, a significant learning curve is required to achieve mastery in:

1. Recognition of the malignant polyp.

2. Performing a good dynamic submucosal injection [4].

3. Endoscopic clipping technique to treat potential bleeding and perforation.

In this issue of Endoscopy, Van der Voort et al. reported the utility and safety of distal cap-assisted EMR (EMR-DC) to treat fibrotic colorectal polyps [5]. Their main objective was to determine the recurrent adenoma rate at first follow-up (6–10 months), and the secondary objective was technical success and safety. The authors performed a prospective, multicentre, observational study involving 70 patients with 70 non-lifting polyps without suspicion of submucosal invasion based on the optical diagnosis. The median polyp size was 25 mm, and the non-lifting area was 15 mm. The polyps were removed by EMR-DC alone (67 %) or required cold avulsion and argon ablation (33 %). The following findings were reported a) the recurrent adenoma rate at first surveillance was 19.7 % b) deep muscle injury (DMI) occurred in 8.9 % of patients.

The authors are commended for conducting a prospective study involving a relatively large number of patients with fibrotic polyps. We, however, recommend the Readers pay particular attention to certain aspects of the study. First, the authorsʼ description of their technique as cap-assisted EMR (EMR-C) can be misleading as it is not identical with the method originally described by Inoue et al. [6]. The EMR-C method was developed primarily for the resection of upper GI tract lesions, including superficial squamous neoplasia, Barrett’s dysplasia, and gastric tumors. Its application in the colon is limited because of the fear of DMI and perforation. In EMR-C, a specialised oblique or straight cap with a notch at the tip is used (K-008 or K-004, Olympus, USA). A crescent-shaped snare (SD-221L-25, Olympus, USA) is pre-looped at the cap's notch. The target mucosa with the lesion is fully suctioned inside the cap and strangled by the snare before applying electrocautery. The capture of the lesion within the snare is mostly blind without direct visualisation. Thus, adequate submucosal injection is mandatory to prevent perforation. As the colon wall is thinner, it should be noted that the application of EMR-C for colonic neoplasia would carry a higher risk for DMI and perforation.

Van der Voort used a distal attachment cap (EMR-DC), which is different from the EMR-C cap. The distal attachment cap is shallow, does not have a specialized groove to seat the snare, and does not require the snare to be pre-looped before capturing the lesion. The use of a shallow cap has the potential for safer resection as it is less likely to catch the full thickness of the colonic wall. However, when used on fibrotic tissue, it is unclear how much of the fibrotic tissue could be drawn inside the cap during suction. We believe this would be a small volume as evidenced by the need for additional therapy in a third of their patients and the higher recurrence rate during the first follow-up. Despite using a shallow cap, the authors encountered DMI in 8.9 % of the cases, requiring endoscopic closure with clips. Second, the authors included polyps with a non-lifting sign and without submucosal invasion based on the optical diagnosis. Non-lifting sign is highly specific (97 %) and accurate (94 %) for detecting invasive cancer in nonpolypoid colorectal neoplasms without prior intervention [7]. About 10% of the included patients had malignant histology after EMR-DC or at follow-up and required surgery. The reason for the inaccurate recognition during optical diagnosis was not explained. The authors also did not report if DMI was encountered in those cases with malignant histology. Lastly, the morphological and pragmatic classification of the lesion appearance might predict the risk of fibrosis and submucosal invasion. Yet, the authors did not report the lesions’ subtype. Lesions that are large in size with a non-granular and pseudo-depressed morphology or those with mixed nodular appearance are at risk of having submucosal fibrosis and invasion, leading to incomplete resection. Although the authors described the morphology of the non-lifting polyps, presenting information on the primary lesion's subtype would help us better understand the reason for incomplete resection and fibrosis [8] [9].

Significant progress has been made in endoscopic imaging technologies and accessories for managing complex colorectal polyps. It is necessary to be adept with the changing technology to deliver the best possible care to our patients. However, the basic principles remain the same, and we need to adhere to them irrespective of the changes. Endoscopic resection must be performed as safely as possible. The risk of immediate or delayed bleeding, perforation, and local or distant recurrence must be kept at a low or negligible rate. Endoscopists need to know how to analyze and interpret the endoscopic features of lesions, understand the risk of lymph node metastasis, carefully select patients and consider their preferences, follow the accepted indication, and adopt standardized resection techniques [8]. Until we master these basic principles of endoscopic resections, several modifications to existing methods will continue to emerge to overcome our deficiencies.

Publication History

Accepted Manuscript online:
27 September 2021

Article published online:
16 December 2021

• References

• 1 Soetikno RM, Gotoda T, Nakashishi Y. et al. Endoscopic Mucosal Resection. Gastrointest Endosc 2003; 57: 567-579
• 2 Soetikno RM, Inoue H, Chang KJ. Endoscopic mucosal resection. Current concepts. Gastrointest Endosc Clin N Am 2000; 10: 595-617
• 3 Moss A, Williams SJ, Hourigan LF. et al. Long-term adenoma recurrence following wide-field endoscopic mucosal resection (WF-EMR) for advanced colonic mucosal neoplasia is infrequent: results and risk factors in 1000 cases from the Australian Colonic EMR (ACE) study. Gut 2015; 64: 57-65
• 4 Soetikno R, Kaltenbach T. Dynamic Injection. Gastrointest Endosc Clin N Am 2010; 20: 497-502
• 5 Van der Voort VRH, Moons LMG, de Graaf W. et al. Efficacy and safety of cap-assisted EMR for treatment of non-lifting colorectal polyps. Endoscopy 2022; 54: 509-514
• 6 Inoue H, Kawano T, Tani M. et al. Endoscopic mucosal resection using a cap: techniques for use and preventing perforation. Can J Gastroenterol 1999; 13: 477-80
• 7 Kobayashi N, Saito Y, Sano Y. et al. Determining the treatment strategy for colorectal neoplastic lesions: endoscopic assessment or the non-lifting sign for diagnosing invasion depth?. Endoscopy 2007; 39: 701-5
• 8 Asokkumar R, Malvar C, Nguyen-Vu T. et al. Endoscopic Assessment of the Malignant Potential of the Nonpolypoid (Flat and Depressed) Colorectal Neoplasms: Thinking Fast, and Slow. Gastrointest Endosc Clin N Am 2019; 29: 613-628
• 9 Soetikno R, Chiu HM, Asokkumar R. et al. Letter to the Editor in Response to "Endoscopic Recognition and Management Strategies for Malignant Colorectal Polyps: Recommendations of the US Multi-Society Task Force on Colorectal Cancer". Gastroenterology 2021; 160: 2216-2220