Been having constipation problems for a bit. had a tiny bit of red stuff on stool. negative colonoscopy. are colonscopys accurate can they miss cancer?

Hemorrhoids, fissure: The most likely cause of the "red stuff" would be hemorrhoids, but a fissure is possible as well. Colonoscopies can miss lesions, such as cancer, but the miss rate is very, very low. Check out the cause for the presumptive rectal bleeding with you gastroenterologist or colorectal surgeon.

Miss rate: A colonoscopy is only as good as the eyes of the colonoscopist doing the procedure. The miss rate for colon cancer on colonoscopy is quoted from 4 to 6 percent. A good colonoscopist will have taken photos documenting that he has used the camera to look back at the rectum. Photos should also be taken of the cecum, appendix and ileocecal valve to prove the camera went all the way to end.