Polypectomy is regarded as high risk for bleeding. Several guidelines recommend continuous use of aspirin during polypectomy. However for clopidogrel, widely used antiplatelet agent, cessation of 5-7 is recommended. There is insufficient data regarding clopidogrel on post polypectomy bleeding. Delayed bleeding after polypectomy in patients with clopidogrel was reported as 3%. A recent study showed that delayed bleeding rate in patients with clopidogrel didn't differ that of who stopped clopidogrel. However the rate for delayed bleeding was 4%, higher than the previous studies. More studies are needed to conclude the safety of polypectomy in clopidogrel users.

Cold snare polypectomy (CSP) can resect polyps without electrical energy. CSP are safe than conventional endoscopic mucosal resection in high risk for bleeding.

The polypectomy techniques in most of studies were heterogenous, where delayed bleeding was investigated in clopidogrel users. There is no study to investigate safety of CSP in patients with clopidogrel users to date. The investigators hypothesized that the bleeding risk of CSP in patients with clopidogrel users would be similar to that of aspirin users.

In this multicenter prospective study, the investigators aimed to compare the safety of CSP between aspirin and clopidogrel users.

• Cold snare polypectomy (CSP): resection of colorectal polyp by mechanical force of snare, without electric cautery.
• Antiplatelet agent: single use of aspirin or clopidogrel
• Uninterrupted (continuous) use of antiplatelet agent: cessation of antiplatelet agent less than 4 days. Cessation of antiplatelet agent is sum of before and after the CSP

ex.)

1. patient who stopped aspirin only on the day of colonoscopy and resumed the day after colonoscopy -> cessation of aspirin was 1 day.

2. patient who stopped aspirin only on the day of colonoscopy and resumed the 2 days after colonoscopy -> cessation of aspirin was 2 days (before colonoscopy 1day + after colonoscopy 1day).

3. patient who stopped aspirin from 3 days before colonoscopy and resumed the day after colonoscopy -> cessation of aspirin was 4 days (-3, -2, -1, 0=on the day of colonoscopy). -> interruption of aspirin -> excluded from study.

4. patient who stopped aspirin from 2 days before colonoscopy and resumed 2 days after colonoscopy -> cessation of aspirin was 4 days (-2, -1, 0=on the day of colonoscopy, 1=the day after colonoscopy). -> interruption of aspirin -> excluded from study.

   • BLEEDING # Immediate (intraprocedural) bleeding After CSP, bleeding will be observed for 2 minutes. Bleeding grade: (1) no bleeding, (2) minor (negligible) bleeding, (3) major bleeding, and (4) active bleeding (spurting).

In case of Grade 3 or 4, hemoclipping will be applied

• Delayed bleeding Delayed bleeding will be defined when all of the following criteria were met: (1) anal bleeding after discharge of endoscopy unit and (2) identification of polypectomy bleeding site by colonoscopy.
• Significant delayed bleeding Any of the following criteria: (1) hemoglobin drop >2, (2) hemodynamic instability, (3) admission, (4) transfusion, and (5) surgery or angiography for hemostasis.

Inclusion Criteria:

• aged 18-80
• polyp size <10mm
• polyp resection : cold snare polypectomy
• cessation of antiplatelet agent less than 4 days

Exclusion Criteria:

• ASA class IV or above,
• hematologic diseases including idiopathic thrombocytopenic purpura, leukemia, and aplastic anemia
• advanced liver cirrhosis
• cessation of antiplatelet agent for 4 days or more
• dual antiplatelet agent users
• coagulopathy (abnormal PT, aPTT, or platelet count)

* Uninterrupted (continuous) use of antiplatelet agent: cessation of antiplatelet agent less than 4 days. Cessation of antiplatelet agent is sum of before and after the CSP

ex.)

1. patient who stopped aspirin only on the day of colonoscopy and resumed the day after colonoscopy -> cessation of aspirin was 1 day.

   (before colonoscopy 1day + after colonoscopy 1day).

2. patient who stopped aspirin from 2 days before colonoscopy and resumed 2 days after colonoscopy -> cessation of aspirin was 4 days (-2, -1, 0=on the day of colonoscopy, 1=the day after colonoscopy). -> interruption of aspirin -> excluded from study.