The purpose of this study is to investigate the accuracy of second generation colon capsule (C2) in evaluating colonic mucosal inflammation of ulcerative colitis patients, using conventional endoscopy as the gold standard.

Consecutive patients with ulcerative colitis will be recruited. Second generation colon capsule endoscopy (C2) and conventional colonoscopy will be performed one after another on the same day. Colonic mucosal inflammation will be scaled by physicians who review C2 videos and those who perform conventional colonosocpies independently. Physicians who review C2 videos and colonoscopists will be blinded to the findings of colonoscopies and C2 videos, respectively.The accuracy of C2 in evaluating mucosal inflammation will be evaluated, using conventional endoscopy as the gold standard.

Inclusion Criteria:

• age 18-80 years
• suspected or known UC
• written informed consent

Exclusion Criteria:

• patients with severe UC according to Truelove and Witts' criteria
• current pregnancy/lactating
• patients with a pacemaker or other implanted electromedical device
• the presence of dysphagia
• patients at higher risk of capsule retention (including Crohn's disease, small bowel tumor, radiation enteropathy, previous intestinal surgery, acute abdominal pain without regular defecation)
• patients with a contraindication to bowel preparation (congestive heart failure, renal insufficiency, a life-threatening condition)
• patients with an allergy to polyethylene glycol, sodium phosphate solution, metoclopramide or bisacodyl suppository