Colonoscopy is the gold standard in the diagnosis of colorectal disease. The success of colonoscopy depends on high-quality bowel preparation by patients. Inadequate bowel cleansing reduces the cecal intubation rate, and the polyp detection rate (PDR). It also increases costs, mostly due to repeated procedures. The quality of bowel cleansing has remained suboptimal even though numerous different products and regimens have been tested and compared in no fewer than six meta-analyses. Therefore, a completely different approach to improve bowel cleansing is welcome.

Here the investigators assume that instant messaging program (Wechat) delivery the detail and FAQ (Frequently Asked Questions) of bowel preparation instructions would improve the quality of the bowel preparation. The Wechat program has some advantages, 1. Wechat supports over 400 million users, nearly half of the mobile subscribers population in China; 2. Wechat provided a real time communications including voice messages, pictures and text exchange timely; 3.Compare with telephone, Wechat is economical of both time and money; 4. Compare with bowel preparation instructional software and litera or cartoon educational booklet, Wechat is more interactive and responsive.

Inclusion Criteria:

• age 18-80
• PEG as purgatives;
• using we-chat software by patients or their relatives
• outpatients

Exclusion Criteria:

• history of colorectal surgery
• known severe colonic stricture or obstructing tumor
• known or suspected bowel obstruction or perforation
• pregnant or lactating women
• patients who cannot give informed consent