It is well known that colonoscopy is the best method to detect and manage precancerous colon lesions. Adenoma detection rate (ADR) is the single most important indicator of the quality of colonoscopy, and complete removal of polyps is a key step in ending polyp carcinogenesis. Microscopic detection and removal of colon polyps can reduce the incidence of colon cancer by 77% and the death rate from colon cancer by 29-37%. However, colonoscopy is not infallible, and the occurrence of interstitial colorectal cancer cannot be ignored due to three main factors: missed diagnosis, denovo cancer development and incomplete removal of polyps. The leakage rate of colonic polyps is 20-40%, 70-80% of interstitial colorectal cancers occur due to missed diagnosis of carcinomas or adenomas, and 10-27% of interstitial colorectal cancers are caused by incomplete removal of polyps.
Ninety percent of polyps found during colonoscopy are less than 1 cm in size, with 10% being about 6-9 mm in size and 90% being about 1-5 mm in size. 1-5 mm size polyps have a 0.5-10% chance of developing highly anisotropic hyperplasia and a 0-0.05% chance of becoming cancerous. Although the chance of these polyps containing high-grade intraepithelial neoplastic or tumor components is extremely low, their complete removal is the key to reducing the incidence of interstitial colorectal cancer. So what are the methods to remove these small polyps?
Cold biopsy forceps polypectomy (CFP)
The technique of removing polyps with biopsy forceps is called cold forceps polypectomy (CFP), and it was found that the complete resection rate of polyps of 1-6 mm size with CFP was 39-89% (multiple bites if one bite cannot be removed).
It was found that the complete resection rate of polyps varied depending on their histological characteristics and the site of the colon where they were located. The complete resection rate was 62% for adenomas, 24% for hyperplastic polyps, 83% for right hemicolectomized polyps, and 33% for left hemicolectomized and rectal polyps. Histopathologic testing of polyps was the only indicator to determine whether they were completely resected. A univariate analysis showed a 97% complete resection rate for adenomas less than 4 mm and a 70% complete resection rate for adenomas 5-6 mm in size. A prospective randomized controlled study showed a 78.8% complete excision rate of polyps when CFP was performed with a large biopsy forceps compared to 50.7% when CFP was performed with a standard biopsy forceps.
CFP often causes a small amount of bleeding, which occurs immediately intraoperatively or delayed postoperatively, but such bleeding is often self-limiting and review of the colon, application of antibiotics, or hospitalization are not necessary. Perforation due to CFP has not been reported.
It is indicated for polyps 1-3 mm in size, and it is simple, safe and effective and can be performed by beginners in endoscopy. However, the lesion should be carefully flushed when performing CFP treatment, otherwise the small amount of bleeding caused by it is likely to lead to incomplete polyp removal.
Hot biopsy forceps polypectomy (HFP)
The technique of applying hot biopsy forceps to remove polyps is called hot forceps polypectomy (HFP), and it is an outdated technique that is often used by endoscopists in their daily practice, although the American Society for Gastrointestinal Endoscopy has recommended avoiding the technique for more than 20 years.
The major difference between HFP and CFP operations is that HFP is electrically powered. By holding the head of the polyp with a thermal biopsy forceps and gently lifting the polyp, an electric current is transmitted from the tip of the forceps through the polyp to the wall of the colon. This operation has been reported to cause damage to the deeper layers of the colonic wall and the submucosal arteries.
A recent study by Metz et al. in an animal model found that HFP can lead to mucosal lateralization in addition to partial (22%) or total (34%) necrosis of the lamina propria, inflammation of the whole lamina propria, and plasmolysis (32%).
The application of HFP is recommended to be avoided mainly for the following reasons.
1, the incomplete resection rate of HFP reaches 17-22% for polyps smaller than 6m.
2, HFP has some complications, such as bleeding, perforation, due to electrocoagulation syndrome to surgery, and even had caused 2 cases of death.
3.Electrocautery causes the destruction of polyp tissue and affects the histopathological examination.
Cold trap polypectomy (CSP)
Cold snare polypectomy (CSP) was first reported by Tappero et al. in 1992. The technique is safe and effective, and its use has gradually increased in recent years: a 2004 survey of 189 gastroenterologists in the United States found that 5% of them used CSP for polyps smaller than 3 mm and 15% for polyps smaller than 4-7 mm in size. A recent survey of 244 endoscopists in Australia found that 75% of them treated polyps less than 3 mm with CSP and 49% treated polyps less than 5 mm in size with CSP. These two large surveys suggest a progressive increase in the use of CSP. CSP is now the best method for complete excision of small polyps in Western societies, but the use of this technique is limited in China, Japan, and other Asian countries.
Operation method: After finding the polyp, open the trap and snare the polyp while gently inhaling to reduce the expansion of the intestinal wall; gradually and gently tighten the trap so that the 2-3 mm of normal mucosa around the polyp is also snared in to ensure complete removal of the polyp. When the polyp is gated off, it is aspirated out through the biopsy orifice.
In recent years, several investigations have shown that CSP is effective in the treatment of small polyps. In a prospective randomized controlled study, Kim et al. found that CSP was significantly more effective than CFP in treating polyps 1-7 mm in size: the complete resection rate of CSP was 97% compared to 82.6% for CFP. The size of polyps is an important factor affecting their complete resection, so polyps of 5-7 mm size should be treated with CSP, while smaller polyps can be considered for CFP.
CSP is a safe and effective technique with few complications, and it is a safe technique without causing vascular damage to the submucosa according to Horiuchi et al. and no perforation has been reported after this procedure.
Recovery of polyps
In a retrospective study of 3060 polyps, Komeda et al. found that 13% were lost after CSP treatment, and other studies have shown a loss rate of 6-14% for small polyps.
It is hypothesized that even with expert manipulation, small polyps are susceptible to loss, especially in the right hemicolon. This is because the proximal colon has more prominent folds in the wall and is less clean than the rest of the intestine. After CSP in the ascending colon, the polyp may fall into the blind area (near the proximal colonic folds) and is likely to be lost unless an inversion is performed in the ileocecal region or other endoscopic devices are used.
There are two main methods for recovering polyps.
1, Removing the polyp and applying endoscopic suction into the biopsy orifice for recovery while it is still in or around the lesion.
2.After the polyp is included in the trap, it is pulled to the biopsy orifice and then gated off and continuously recovered by suction. The efficiency of the first method is 100%, and the efficiency of the second method is 90%.
To cut or not to cut, to do pathology or not to do pathology?
Hassan et al. studied 18 549 patients with small colon polyps and found that 51% of them were adenomas and 0.04-0.08% contained high-grade intraepithelial neoplastic, villous, or tumor components. Because of the extremely low incidence of high-risk pathological components in small polyps, some scholars question whether they should be removed. Innovative advances in technology have made optical diagnosis possible, and the application of endoscopic enhancement techniques has revealed that 90% of small colon polyps contain an adenomatous component. The development of optical endoscopy research and the extremely low chance of cancer in small colon polyps made the significance of pathological histological testing of small polyps questioned for the first time.
So how accurate is the endoscopic diagnosis of polyps?
Several studies at academic and non-academic endoscopy institutes have shown that the odds of an endoscopic optical diagnosis of small colon polyps being consistent with pathologic histology are 80-83%, possibly due to inadequate training of some community-based physicians in optical diagnostic skills. Two studies have shown that after training of physicians, the odds that the nature of endoscopic optical diagnosis of small colonic polyps is consistent with pathological histology is 90%. And Raghavendra et al. found that the accuracy of endoscopic diagnosis of the nature of small polyps could be increased from 48% to 91% after endoscopists were trained.
Recently, guidelines published by the European Society of Gastrointestinal Endoscopy encourage the use of real-time optical diagnosis instead of histopathology for the diagnosis of small colorectal polyps (<5 mm) under strictly controlled conditions.
Conclusion
Small polyps (1-5 mm) are the most common type of lesion we encounter during colonoscopy and have a very low chance of containing anisotropic proliferative or neoplastic components, but their complete excision is key to reducing the incidence of interstitial colorectal cancer.CFP is safe and effective for treating polyps 1-3 mm in size, and polyps 4-5 mm in size should be treated with CSP, while HFP should be avoided.