Colonoscopy is a form of endoscopy used to view the large intestine.
In this video, the intestinal lining initially appears smooth and normal, but a bulging, discolored, and abnormal growth is later seen.
Next, small clippers attached to a metal wire are inserted through the endoscope and used to grab a sample of the growth and remove it for biopsy. The small amount of blood seen is normal after a biopsy.
(Video has no audio.)
Courtesy of Jerome D. Waye, MD.