Will submucosal injection for colonic polyps get left out in the cold?

Cold snare resection is now recommended for adenomatous polyps <10 mm in size, and there is a growing body of evidence supporting its use for polyps larger than this [1] [2]. For sessile serrated lesions, cold snare resection has been repeatedly demonstrated to be successful, regardless of the lesion size, with or without submucosal injection, possibly owing to the ease of transection and the lack of submucosal fibrosis within sessile serrated lesions [3]. In this issue of Endoscopy, do Espirito Santo et al. report a systematic review and meta-analysis of 1556 patients from seven randomized controlled trials that compared cold snare resection versus cold snare endoscopic mucosal resection (C-EMR) using submucosal injection for colonic polyps and found there was no difference in the rates of complete resection, en bloc resection, and adverse events, although C-EMR did have a longer procedure time [4].

Submucosal injection relies on the principle of creating a submucosal cushion to protect the underlying muscle layer from injury or, even worse, perforation. Owing to the reduced depth of resection and the lack of electrocautery use in cold snaring, muscle injuries and perforations are extraordinarily rare. Cold snare resection is known for its higher rate of immediate bleeding than resection using electrocautery, but almost all bleeding after cold snare resection can be stopped with conservative techniques, such as applying tamponade with the waterjet or the scope itself, without the need for clips. The overwhelming safety of cold snare resection should inspire confidence in endoscopists – submucosal injection is likely not needed to reduce the procedure risks for any size of polyp.

“As cold snare resection sees expanding indications, submucosal injection may be left out in the cold and only brought in when turning on the heat.”

If there is no difference between the adverse events for cold resection, why lift? Possibly the answer is to delineate the borders of the lesion to ensure complete resection. The majority of the polyps in this meta-analysis were <10 mm in size, which are easily removed en bloc with a cold snare. Lifting is unnecessary in this size range. With high definition endoscopes, magnification, virtual chromoendoscopy, and meticulous inspection, lifting may also be unnecessary for polyps of >10 mm. Additionally, one may use the pressurized waterjet to expand the defect, which can allow for easier inspection of the margins. More studies are needed to understand how submucosal injection affects complete resection for polyps >10 mm.

When performing cold snare resection, one should ensure an adequate depth of resection. Additionally, because of the safety of cold snaring, there should be no hesitation in resecting a wide rim of normal tissue around the defect, in an effort to completely eliminate any polyp tissue and reduce possible recurrence. Adequate technique is vital for successful cold snare resection to ensure complete resection, including having the lesion at 5–6 o’clock, placing the snare over the polyp with an adequate rim of normal tissue, anchoring the shaft of the snare so as to prevent slippage of the snare toward the polyp during snare closure, and then resecting. Studies of incomplete resection and high polyp recurrence rates when using cold snaring should also focus on ensuring adequate technique among all of the participating endoscopists.

With the proliferation of techniques, such as endoscopic submucosal dissection and full-thickness resection, there is a growing emphasis on and ability to perform en bloc resection. Given that all widely available dedicated cold snares are approximately 10 mm, it is not feasible to perform en bloc resection on lesions larger than this, while ensuring an adequate rim of normal tissue. Instead of bundling tissue and possibly having to “pull” it through by applying tension outside the scope, frequently leading to a submucosal cord, which arguably may increase the risk of residual polyp tissue or complications [5], cold snare resection of polyps >10 mm should be undertaken in a piecemeal fashion, with adequate depth and surrounding normal tissue also removed.

Malignancy in colonic polyps can often be identified by surface features and morphology. The risk of cancer in polyps in the range 10–19 mm is rare [6]. Even some polyps >20 mm, such as those that are granular or classified as Paris IIa/IIb, have a low risk of submucosal invasion [7]. Beyond the use of submucosal injection or lesions not for cold snare resection, we should also be asking about the limits of cold snare resection in general, given its safety profile compared with other techniques. More studies are needed to understand which large adenomatous lesions in the colon can be routinely resected with cold snare resection and whether submucosal injection is needed.

The article by do Espirito Santo et al. should put an end to the practice of submucosal injection for polyps <10 mm; however, the lack of evidence for polyps ≥10 mm leads to further questions that could not be answered by the authors with the available studies. Advancements in technology and technique are exciting as endoscopists continue to push the limits of what can be safely accomplished; however, we should acknowledge the simplicity, safety, affordability, and potential of cold snare resection – rarely are clips needed, no injection fluid is needed at least in polyps <10 mm and maybe even larger than this, and delayed risks are rare. The downside is the potential risk of recurrence for larger polyps. With the growing emphasis on sustainable endoscopy across the world, reducing the use of a needle, lifting agent, and the time of the procedure all add up to financial and carbon costs potentially being saved [8].

Further areas of investigation include more randomized trials comparing cold snare resection and C-EMR for polyps >10 mm and exploring how cold snare resection with an emphasis on technique can be effective for certain polyps >20 mm, specifically those that have a low risk of covert submucosal invasion. As studies seek to answer these questions and cold snare resection sees expanding indications, submucosal injection may be left out in the cold and only brought in when turning on the heat.

Publication History

Article published online:
29 April 2024

• References

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