It is necessary to retrieve the resected polyp to determine the pathological nature of polyp and to judge the completeness of resection in polypectomy. For polyps with a larger diameter (>5mm), the most reliable way to retrieve them is to suck them out with the colonoscope. However, this method requires multiple colonoscope insertions, resulting in prolonged operation time and increased patient suffering. Therefore, clinicians often receive polyps by pressing the colonoscope suction valve. But it is difficult to receive polyps or even fail to receive. Even if the polyps were successfully received by this method, many polyps were fragmented. When the polyp is fragmented, the pathologist cannot be sure of the completeness of the polyp removal.

By removing the colonoscope suction valve and connecting a polyp trap to suction onto the instrument channel port, the polyp fragmentation rate was reduced greatly. To further reduce the polyp fragmentation rate, while reducing the operation time and colon insertions, we applied the polyp receiving bag in colonoscopy operations. The primary purpose of this study is to evaluate the effectiveness of the application of the polyp retrieving bag to reduce the polyp fragmentation rate.

After polyp resection, it is necessary to retrieve the resected polyp to determine the pathological nature of polyp and to judge the completeness of resection in polypectomy. For polyps with a small diameter (≤5mm), usually by pressing the suction valve button of the colonoscope, polyps could be completely retrieved through a trap. For polyps with a larger diameter (>5mm), the most reliable way to retrieve them is to suck them out with the colonoscope. However, this method requires multiple colonoscope insertions, resulting in prolonged operation time and increased patient suffering. Therefore, clinicians often receive resected polyps with larger diameters by pressing the colonoscope suction valve. However, it is difficult to receive polyps or even fail to receive. Even if the polyps were successfully received, many polyps were fragmented, and the polyp fragmentation rate can be as high as 36.6%~ 60.3%. When the polyp is fragmented, the pathologist cannot be sure of the completeness of the polyp removal. Due to the possibility of malignant transformation in some polyps, the completeness of polyp resection is essential to guide the following treatment.

Some effective methods were developed to reduce polyp fragmentation, including removing the colonoscope suction valve and connecting a polyp trap to suction onto the instrument channel port. The resulting polyp fragmentation rates are 22.4-43.0% and 18.5%, respectively. To further reduce the polyp fragmentation rate, while reducing the operation time and improving the efficiency of the operation, we applied the polyp receiving bag in colonoscopy operations. In a previous pilot study, the polyp receiving bag has been applied in clinical practice, and its polyp fragmentation rate and polyp recovery failure rate are quite low. The primary purpose of this study is to evaluate the effectiveness of the application of the Polyp retrieving bag to reduce the polyp fragmentation rate.

Inclusion Criteria:

1. Single polyp, with a diameter of 5-15mm,
2. Written informed consent.

Exclusion Criteria:

1. Polyps that were not removed en bloc,
2. Underlying bleeding disorder,
3. The platelet count less than 50×10^9/L,
4. Serious cardio-pulmonary, hepatic or renal disease,
5. Intolerance to endoscopy,
6. Other high-risk conditions or disease (such as massive ascites, etc.),
7. Pregnancy.

Patients were not informed about their randomization allocation in order to increase reliability during follow-up.