What’s the Difference Between Colonoscopies & Sigmoidoscopies?

Colonoscopy and sigmoidoscopy are similar in a number of ways: both are tests that allow doctors to see inside the large intestine. Doctors use colonoscopies and sigmoidoscopies to diagnose a number of health problems. There are differences between the two procedures, though, and these differences can be important.

Understanding the Intestines

The large intestine measures about six feet long and is about three inches wide. Its main job is to absorb water along with some nutrients and electrolytes from the stool. This long, tubular organ also produces and absorbs some vitamins, and forms feces for elimination from the body.

The large intestine has three main parts: the colon, rectum, and anus. Food waste moves through the colon to the rectum and then onto the anus, where it is eliminated from the body. Specifically, food waste moves into the cecum, which is the beginning of the colon. It then travels up through the ascending colon on the right side of the abdomen, across the abdomen through the transverse colon, and down through the descending colon.

Food waste then moves to the sigmoid colon, which is the last portion of the large intestine. The sigmoid colon connects the large intestine to the rectum. Its function is to store fecal wastes until they are ready to leave the body through the rectum and anus.

Colonoscopies and sigmoidoscopies help doctors detect and diagnose problems affecting these structures within the large intestine.

The Difference between Sigmoidoscopy and Colonoscopy

Both sigmoidoscopy and colonoscopy use a camera attached to a thin flexible tube to help doctors view the inside of the large intestine. There are some major differences between the two, though. The primary differences are the areas of the intestines examined and the conditions each can detect.

Colonoscopy is a thorough examination of the large intestine in its entirety, from the cecum to the sigmoid colon.

Doctors use colonoscopies to diagnose a number of digestive conditions, including:

• Colon cancer
• Colon polyps that may be cancerous or become cancerous
• Crohn’s disease
• Ulcerative colitis
• Diverticulosis
• Hemorrhoids

In a sigmoidoscopy, doctors examine only the rectum and the sigmoid. A sigmoidoscopy helps doctors diagnose ulcerative colitis and polyps that might become colon cancer.

A sigmoidoscopy is less invasive than a colonoscopy, so doctors often start with a sigmoidoscopy if they suspect a condition affecting only the sigmoid and not the rest of the colon. Doctors typically recommend that patients undergo colonoscopy if they find polyps on sigmoidoscopy, as if polyps develop in the sigmoid colon, they are likely to develop elsewhere.

For more information on colonoscopies and sigmoidoscopies, or to learn more about each of these important procedures, contact the GI professionals at Allied Digestive. Our gastroenterologists are glad to help.