Blank is a diagnostic procedure preformed by a gastroenterologist. The doctor uses a long, thin tube that has a tiny video camera at the end. The doctor has to be skilled to guide the tube into the GI tract.

Colonoscopy

Explanation:

When performing colonoscopy, the gastroenterologist uses a long, thin, flexible tube with a tiny video camera and a light on the end — called the colonoscope — to view the entire colon and rectum and check for polyps, inflammatory changes or cancer.