CT scans, especially if it didn't include contrast, can easily miss things seen on a colonoscopy.
Emergency Rooms do CT scans because they're cheaper and quicker, and they can usually find life-threatening things like leaks, toxic megacolon, blockages, etc, but they often miss inflammation.
Follow up with your gastroenterologist and let him/her know you went to the ER for pain.
edited to fix spelling/grammarPost Edited (beave) : 2/19/2017 7:15:17 PM (GMT-7)