Why do doctors pump air into the colon during a colonoscopy?

To see. Often the colon is collapse. A doctor can either inflate air or c02 to expand the colon to see the folds. On the colonoscopy withdrawal, the doctor will then attempt to suction the air to reduce the colon distension and patient discomfort.
For visibility. When the colon is properly prepped and empty, we have to put air or nitrogen in to distend the colon to allow for visibility and accuracy to visualize the mucosal surface.