Patients with constipation are more likely to have poor bowel preparation quality due to slow gut motility and poor emptying ability. Gum chewing, as a proxy of sham feeding, is a very simple way used to accelerate gut motility. And a previous study found that enhanced instructions by WeChat could improve bowel preparation quality. Thus, investigators conducted a single-center randomized controlled trial to explore the effect of chewing gum combined with manual enhanced instructions by WeChat on the bowel preparation quality for colonoscopy in patients with constipation.

In this randomized controlled trial, consecutive outpatients with constipation for colonoscopy are screened and then randomized into two groups. All enrolled patients will receive 3 liter polyethylene glycol (PEG) for bowel preparation. Patients in the chewing gum and WeChat group (n = 75) are further advised to chew one piece of sugarless gum for 20 minutes after drinking each 1 liter PEG; additionally, they will receive enhanced instructions via WeChat before two days and one day of colonoscopy to further inform how to chew gum and highlight the importance of adequate bowel preparation. Patients in the control group (n = 75) are guided by regular instructions.

Inclusion Criteria:

1. Patients undergoing colonoscopy at the Department of Gastroenterology of the General Hospital of Northern Theater Command.
2. Patients aged ≥18 years, no gender limitation.
3. Patients who sign informed consent.
4. Patients who are diagnosed with constipation.

Exclusion Criteria:

1. Patients who are pregnant or breastfeeding.
2. Patients who are allergic to polyethylene glycol.
3. Patients who are suspected with intestinal obstruction, stenosis or perforation.
4. Patients with mental illness.
5. Patients with serious heart, brain, liver, and kidney diseases.
6. Patients who use WeChat unconditionally by themselves or their family members.
7. Patients who are allergic to chewing gum related ingredients.
8. Patients with the history of colorectal surgery.