Author names: Dr Mairéad McNally and Dr Mo Thoufeeq
Author institutions: Sheffield Teaching Hospitals
- Endoscopic Resection
- Cold Snare
- Hot Snare
CSP – Cold snare polypectomy
HSP – Hot snare polypectomy
EMR – Endoscopic Mucosal Resection
SSL – Sessile Serrated Lesion
BSG – British Society of Gastroenterology
ESGE – European Society of Gastrointestinal Endoscopy
- Cold snare polypectomy is best for benign flat or sessile polyps <10mm.
- Current European guidelines recommend hot snare for flat or sessile polyps between 10-19mm but there is emerging evidence to support the use of cold snare for these polyps, allowing avoidance of deep thermal injury associated with the use of diathermy. CSP is also a feasible option for the removal of non-dysplastic SSLs >10mm. Individualised assessment of polyp morphology and patient factors should facilitate decision-making regarding resection choice in polyps between 10mm and 20mm.
- Hot snare polypectomy/EMR is generally used for benign flat or sessile polyps >20mm and pedunculated polyps
Endoscopic removal of colorectal polyps has been shown to reduce the incidence and mortality from colorectal cancer 1. Polypectomy techniques and equipment are continually evolving and endoscopists must maintain awareness of emerging data on the subject. The key to performing high-quality polypectomy is choosing the right polypectomy technique based on polyp characteristics. In this article, we present a case of a 19mm flat caecal lesion within a tattoo removed by piecemeal EMR, and we review the role of hot and cold snare polypectomy in the management of colorectal polyps.
A flat 19mm polyp was identified in the caecum of a healthy 44 year-old female who underwent colonoscopy for evaluation of chronic diarrhoea (Image 1). The polyp was referred for polypectomy on a therapeutic colonoscopy list. A tattoo had been applied at the index colonoscopy (Image 2). Although the tattoo injection site was on the anal side of the polyp, there was an unintended submucosal spread of the tattoo, resulting in ink encircling the polyp.
Conscious of the perforation risk in the caecum, we considered the option of piecemeal cold snare polypectomy (CSP) for this polyp. However, we anticipated difficulty removing the polyp due to the presence of the tattoo in the polyp base. After an initial assessment of the surface and vascular pattern, we used a submucosal solution containing dilute adrenaline, indigo carmine, and gelofusine to lift the polyp. A good submucosal lift was achieved (image 3), and a decision was made intra-procedurally to proceed with hot snare polypectomy. The polyp was removed piecemeal with the hot snare. Although there were no intraprocedural complications, we applied 2 clips to the polypectomy site. Histology confirmed a sessile serrated lesion. The decision regarding the use of hot vs cold snare is not always clear-cut. We looked at the evidence to support decision-making in a case such as ours.
Key Polypectomy Considerations
High-quality polypectomy focuses on complete polyp resection and retrieval for histological analysis with minimal risk. Although post-colonoscopy colorectal cancers are mainly attributed to missed lesions, it is estimated that up to 27% of interval cancers could result from incomplete polyp resection 2,3. It is a common occurrence and may occur in up to 10% of polypectomies for polyps between 5 & 20mm 4. Larger size and sessile serrated lesions (SSLs) are predictors of incomplete resection 4, but polypectomy technique also plays a role. Piecemeal technique and intraprocedural bleeding negatively impact the completeness of resection 5.
Cold Snare Polypectomy (CSP)
Current ESGE guidelines recommend CSP as the preferred technique for all diminutive (<5mm) colorectal polyps 6. Cold forceps removal is no longer recommended due to high rates of incomplete resection and should be reserved for lesions <3mm where snare polypectomy is technically difficult 7,8. CSP is also preferred for small non-pedunculated polyps (6-9mm) due to a better safety profile when compared with hot snare polypectomy (HSP) – rates of delayed bleeding, perforation, and post polypectomy syndrome are lower in CSP and it has the advantage of shorter procedure time than HSP.
Hot Snare Polypectomy (HSP)
HSP (without or without injection of the stalk) is recommended for all pedunculated polyps, and endoscopic mucosal resection is generally used for non-pedunculated polyps greater than 20mm.
There is limited research on the optimal diathermy settings 5 and practice varies widely 9,10. A pure cutting current provides high-quality incision and reduced thermal injury but leads to higher rates of immediate post polypectomy bleeding 11. For this reason, European guidelines advise against a pure cutting current6.
On the other hand, pure coagulation current has good haemostasis properties but increases the risk of thermal tissue injury. A forced coagulation current may be used in left-sided pedunculated or sub-pedunculated polyps where a large feeding vessel is suspected within the stalk 12 but BSG guidelines recommend against a prolonged coagulation current due to increased risk of delayed post-polypectomy bleeding and thermal injury 10. Diathermy-induced perforation is a concern, particularly in the right colon where the wall is thinner.
Automatic microprocessor technologies can be used to achieve a blend of coagulation and cutting current and are recommended by ESGE 6. This automatically balances the need for haemostasis with the prevention of deep thermal injury. Endoscopists should be familiar with the equipment used in their unit. Some endoscopists prefer to manually adjust settings, but this is not usually needed with modern-day diathermy machines.
Injection of a solution into the submucosal space reduces the risk of thermal injury and can improve polyp resection rates 13. Several solutions are available for this purpose. The best studied are normal saline and sodium hyaluronate. A 2016 meta-analysis with data from nine randomised controlled trials on EMR concluded that available evidence indicates there is no solution with a superior effect on resection rates 14. In particular, no difference was identified between the effects of normal saline and sodium hyaluronate on resection rates. Additionally, no single solution was found to reduce the risk of post-polypectomy bleeding or incidence of perforation 14. More research is required to further evaluate the impact of solutions on resection and complication rates. In the absence of definitive data to dictate the choice of solution, the endoscopist should aim to provide submucosal lift with a solution he/she is familiar and comfortable with, bearing in mind that more viscous solutions require a smaller volume of injection and last longer. US guidelines support the use of a viscous injection solution for EMR of lesions >20mm to minimise resection time 15. In practice, many endoscopists in the UK opt for a colloid-based EMR solution.
There appears to be variation in practice regarding tattooing too. Tattoos within the colon are intended to mark lesions for later endoscopic resection, surgical resection or to mark a resection site for easy endoscopic follow-up. Since the caecum is a reliable landmark for both endoscopic and surgical resection, it is not recommended to tattoo caecal polyps 6,10. The application of a tattoo in our case was outside of standard practice and impacted subsequent management. Endoscopists should be aware of the potential for tattoos to induce submucosal fibrosis, and where tattooing is appropriate, take care to avoid tattooing a polyp base by aiming at least 3cm from the lesion 10.
The Debated Lesions
10-19mm non-pedunculated polyps
There is some debate surrounding the optimal management of non-pedunculated 10-19mm polyps 16. HSP after submucosal lifting is currently recommended first-line by ESGE 6 although US guidelines support either cold or hot snare polypectomy with or without submucosal injection for non-pedunculated 10-19mm polyps 15. HSP can achieve en-bloc resection and provide good histological specimens. However, the evidence supporting the use of HSP over piecemeal CSP in these 10-19mm polyps is limited.
The main concern with HSP is that it comes with a risk of deep mural injury prompting some endoscopists to opt for piecemeal CSP in cases where concern regarding perforation is high.
CSP and Cold EMR reduce the risk of thermal injury so the risk of perforation, post-polypectomy syndrome, and delayed bleeding is reduced. This may be an important consideration in patients taking antiplatelet or antithrombotic agents. A 2019 systematic review evaluating cold snare resection for non-pedunculated polyps >10mm (8 studies, 522 polyps, median size 17.5 mm) reported a complete resection rate of 99.3% and a recurrence rate of 4.1% at follow-up 17. Recurrence rates after CSP were comparable to those recorded for hot EMR 17.
Sessile Serrated Lesions >10mm (SSLs)
The literature is limited on the optimal resection method for SSLs >10mm. CSP and cold EMR are becoming increasingly popular techniques to remove these lesions without exposing patients to the risks of electrocautery as many SSLs are found on the right side of the colon. Piecemeal cold EMR is expected to emerge as the standard of care for resection of SSLs >10mm 13,18.
Several studies have demonstrated the safety of cold snaring for SSLs 19–22. Tate et al. report on the safety of piecemeal CSP without submucosal injection in a series of 41 SSPs (mean size 15mm) 20. They recorded no cases of intraprocedural bleeding, perforation, delayed bleeding, or post polypectomy syndrome. In another series of 163 SSLs >10mm (mean size 17.5mm) removed by cold EMR, only 3 minor adverse events were recorded with no delayed bleeding 21. A 2021 single-centre retrospective study examined the feasibility of CSP for 10-20mm SSLs 22. In this recent study, 160 SSLs sized 10-20mm with no evidence of dysplasia or cancer using WLI and magnification with BLI or NBI were removed using by CSP. 3-6month follow-up was provided for lesions removed with piecemeal CSP or with evidence of dysplasia or malignancy on histology. All other SSLs were followed-up at 1-2year intervals. There were 2 cases of intraprocedural bleeding but no post-procedural haemorrhage. The polyp recurrence rate in 101 polyps was 5% (median follow-up of 18 months). All recurrent cases were treated with repeat CSP. No perforations were recorded. This study suggests that CSP is a safe option for the management of non-dysplastic SSLs of 10-20mm but close follow-up is recommended.
There are some practical issues to consider with CSP. From a technical perspective, CSP is associated with higher rates of superficial intra-procedural oozing 5. Whilst this is not clinically relevant, it can obscure views and make complete polyp resection more challenging. The main disadvantage of CSP for 10-19mm lesions is that it may not achieve en-bloc resection and, therefore, in theory, poses a higher risk of incomplete polyp resection. Using a submucosal lift with dye for piecemeal Cold EMR technique can help to delineate the lateral borders of the polyp, especially for flat lesions, and minimise incomplete-resection risk. Furthermore, the addition of dilute adrenaline to the lifting solution reduces oozing by promoting vasoconstriction and allows the endoscopist to maintain clear views. Using a water jet that is targeted at the mucosal defect, causing expansion of submucosa may also help to assess the completion of therapy.
Piecemeal cold resection results in fragmented histological specimens. In practice, however, even lesions removed en-bloc by HSP in the right side of the colon are sometimes deliberately fragmented by the endoscopist in situ to allow polyps to be suctioned through the channel of the scope rather than depending on a Roth net for removal. Use of a Roth net to remove a right-sided lesion leads to limited views and the need for the scope to be reinserted after retrieval of the polyp.
To date, there have been no randomised controlled trials comparing hot snare EMR and piecemeal cold snare resection for 10-19mm polyps 5. Many endoscopists will proceed with hot snare EMR for right-sided lesions and attempt to minimise associated risk with the use of submucosal injection, underwater techniques, and post-procedural clip placement.
With shorter procedure times and fewer complications, CSP is the preferred method for the removal of polyps <10mm. HSP remains the recommended technique for resection of 10-19mm benign flat or sessile polyps but CSP is emerging as a viable alternative for polyps in this category. CSP is also now used for SSLs >10mm in size. The limitations of CSP include intraprocedural ooze, theoretically increased risk of incomplete resection, and fragmented histological specimens, but can be offset by the use of submucosal lift and careful post-polypectomy site inspection. Hot snare remains the primary modality for resection of benign polyps >20mm and pedunculated polyps. Optimal diathermy settings are debated but the use of a blended current using automated microprocessor technologies is generally safe and effective. Get to know your local technology and equipment. Polyp and patient characteristics should prompt the endoscopist to weigh hot versus cold snare polypectomy for individual patients.
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Dr Mairéad McNally is a Clinical Fellow at Sheffield Teaching Hospitals (STH) where she is undertaking focussed training in complex polypectomy with Dr Mo Thoufeeq. She is the current Endoscopy Lead for the recently established Colorectal Screening Programme for Cystic Fibrosis Patients at STH. Her research focusses on improving outcomes in endoscopy through adequate patient preparation and the role of artificial intelligence in endoscopy.
She completed her Specialist Training in Gastroenterology and General Internal Medicine through the Royal College of Physicians in Ireland. She holds a Master’s Degree in Leadership and Innovation in Healthcare. She recognises the role of education in promoting innovation in service development. She is a faculty member for the BSG EQIP Haemostasis Course and former Honorary Clinical Lecturer at Trinity College Dublin.
Dr Mo Thoufeeq is a Consultant Gastroenterologist with an interest in GI endoscopy. He is an honorary senior clinical lecturer at the University of Sheffield. He is an elected member of the British society of gastroenterology (BSG) endoscopy clinical research committee. He is an active member of the BSG endoscopy quality improvement programme (EQIP) team and the lead for Yorkshire. He is a Bowel cancer screening programme (BSCP) accredited colonoscopist and a faculty member of Sheffield endoscopy training centre.
He is a member of the standard-setting group of the Specialty Certificate Examination (SCE) Gastroenterology, Royal College of Physicians (RCP), UK. He offers a fellowship programme in EMR in Sheffield. He is involved with training internationally and is the BSG international committee’s communication lead. He has run endoscopy courses in Malta and Cairo.
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