MSD Manual

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Jonathan Gotfried

, MD, Lewis Katz School of Medicine at Temple University

Full review/revision Apr 2021 | Modified Sep 2022
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Endoscopy is an examination of internal structures using a flexible viewing tube (endoscope). Endoscopy can also be used to treat many disorders because doctors are able to pass instruments through the tube.

When passed through the mouth, an endoscope can be used to examine the esophagus (esophagoscopy), the stomach (gastroscopy), and part of the small intestine (upper gastrointestinal endoscopy).

When passed through the anus, an endoscope can be used to examine the rectum (anoscopy); the lower portion of the large intestine, the rectum, and the anus (sigmoidoscopy); and the entire large intestine, the rectum, and the anus (colonoscopy). For procedures other than anoscopy and sigmoidoscopy, people are typically given drugs by vein (intravenously) to calm them and prevent discomfort (sedation).

Viewing the Digestive Tract with an Endoscope

A flexible tube called an endoscope is used to view different parts of the digestive tract. When passed through the mouth (as shown on the left), an endoscope can be used to examine the esophagus, stomach, and some of the small intestine. When passed through the anus (right), an endoscope can be used to examine the rectum and the entire large intestine.

Viewing the Digestive Tract with an Endoscope

Endoscopes range in diameter from about ¼ inch (a bit more than ½ centimeter) to about ½ inch (1¼ centimeters) and range in length from about 1 foot (about 30½ centimeters) to about 6 feet (almost 2 meters). The choice of endoscope depends on which part of the digestive tract is to be examined. The endoscope is flexible and provides both a lighting source and a small camera, which allows doctors to get a good view of the digestive tract lining. Doctors can see areas of irritation, ulcers, inflammation, and abnormal tissue growth. Some endoscopes have ultrasound probes on the tip. Images from these probes can show details that ultrasound probes placed on the person's skin cannot.

Endoscopy: Viewing the Stomach

Doctors can use endoscopes to screen people for certain disorders, such as colon cancer Screening tests Family history and some dietary factors (low fiber, high fat) increase a person’s risk of colorectal cancer. Typical symptoms include bleeding during a bowel movement, fatigue, and weakness... read more Screening tests . For example, people who are at high risk of developing colon cancer and people who are age 45 to 50 and older should undergo colonoscopy to detect polyps or other changes. Colonoscopy should be done every 10 years in people who have no risk factors for colon cancer or more frequently or at an earlier age in people who have had polyps in the colon Polyps of the Colon and Rectum A polyp is a projecting growth of tissue from the wall of a hollow space, such as the intestines. Some polyps are caused by hereditary conditions. Bleeding from the rectum is the most common... read more Polyps of the Colon and Rectum or have a family history of colon cancer.

Small tools can be inserted through endoscopes and used to take tissue samples (endoscopic biopsy). These samples can then be evaluated for inflammation, infection, or cancer. Because the lining and the inner layers of the walls of the digestive tract do not have nerves that sense pain (with the exception of the lower part of the anus), this procedure is painless.

Endoscopes can also be used for treatment. A doctor can pass different types of instruments through a small channel in the endoscope. An electric probe at the tip of the endoscope can be used to destroy abnormal tissue, to remove small growths, or to close off a blood vessel. A needle at the tip can be used to inject drugs into dilated veins in the esophagus and stop their bleeding.

Colonoscopy: Obtaining a Biopsy Sample

Before having any endoscopic procedure, a person must avoid food for 8 hours and avoid liquids for 2 to 4 hours before the procedure. Food in the stomach can block the doctor’s view and might be vomited up during the procedure. Before having an endoscope passed into the rectum and colon, a person usually takes laxatives and is sometimes given enemas to clear out any stool. For some procedures, people may need to consume only liquids (such as gelatin or broth) the day before the procedure.

Complications resulting from endoscopy are relatively rare, and most are related to the drugs used for sedation. Although endoscopes can injure or even perforate the digestive tract, they more commonly cause irritation of the tract lining and a little bleeding that typically goes away on its own.

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