Harvard Health Letter

By the way, doctor: Does a colonoscopy reach the ileum?

Q. I am scheduled to have a colonoscopy soon. Does the examination reach the ileum?

A. The ileum is the last 12 feet or so of the small intestine. It connects to the cecum, the bulbous cul-de-sac that forms the beginning of the colon (the appendix hangs off the cecum). Space is at a premium in our abdomens, so the ileum and the rest of the small intestine are folded up and tucked inside the archway created by the colon's ascending, transverse, and descending sections.

Colonoscopy is performed using an endoscope, a flexible tube that allows a doctor to place his or her eye at one end and see clearly what's at the other end. But endoscopes aren't just for seeing. Doctors also use instruments at the far end of the endoscopes to perform biopsies, give injections, and surgically remove small growths (polyps) to check for cancer. A colonoscopy is an examination of the entire length of the colon. It has largely replaced the barium enema, the previous technique for examining the colon.

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