All the patients who had been targeted were registered.

The aim of this study is to clarify the factors influencing quality of bowel cleansing for colonoscopy in patients with colorectal cancer surgery and confirm the adequate bowel cleaning method for patients with colorectal cancer surgery. Through this, ultimately in patients with a history of colorectal cancer who have high risk of colorectal cancer, it could be possible to detect cancerous lesions early and increase the survival rate.

This study is based on observational study Subjects are the patients with colorectal cancer surgery who visits the out patients clinic for follow-up colonoscopy The patient's medical records on the basis of information collected at the point of the colonoscopy performed Quality of bowel cleansing is calculated with the Boston bowel preparation scale Patient compliance and satisfaction are measured.

Inclusion Criteria:

• age ≥ 20
• patients who underwent colorectal cancer surgery
• patients who underwent follow-up colonoscopy as a conventional medical procedures

Exclusion Criteria:

• age < 20
• patients who have ileus or bowel obstruction
• patients in pregnant status
• Patients who did not consent to research

patients undergoing colonoscopy after colorectal cancer surgery