Symptoms that require Diagnosis or Treatment with Colonoscopy

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A person undergoing a colonoscopy must lie on their left side during the procedure. They are usually lightly sedated to help them relax, and they may also receive medication to prevent pain. Medical personnel are on hand to monitor vital signs and help the person remain comfortable.

During the procedure, a doctor inserts a colonoscope into the anus. The colonoscope is a long, thin, flexible tube with a light source. A miniature camera is mounted at the end of the tube. The tube is guided through the rectum and colon to the beginning of the small intestine, and the tiny camera transmits images to a computer screen. As the tube moves, carbon dioxide gas is used to inflate the large intestine so that the doctor can more easily examine the tissues.

When the colonoscope reaches the beginning of the small intestine the tube is slowly removed. The doctor examines the rectum and colon a second time before fully withdrawing the colonoscope.

When is a Colonoscopy carried out?

Colonoscopy can be carried out for both diagnostic and treatment purposes. Any of the following symptoms may prompt a colonoscopy:

  • Abdominal pain or bloating
  • Anemia
  • Blood in stool
  • Chronic diarrhea or constipation
  • Unexplained weight loss
  • Colonoscopy is also used to screen for colon cancer

Certain diseases may also be treated via colonoscopy. When ulcers or other lesions within the colon bleed, these can be treated with cauterization or the application of medication to stop the bleeding.

Colon polyps, which can be cancerous or may develop into cancer, can be removed through the colonoscope with an instrument shaped like a lasso. This is an effective preventative treatment for colon cancer, as almost all cases of this cancer develop from colon polyps.

During colonoscopy a doctor can also take samples of any tissue that appears abnormal, such as polyps, ulcers, and other types of lesions. As with polyp removal, a tool is passed through the colonoscope to remove the sample of tissue. The sample that is taken is called a biopsy, and is usually sent to a laboratory to be tested for signs of disease.


Colonoscopy information at the National Institute of Diabetes and Digestive and Kidney Diseases at the National Digestive Diseases Information Clearing House

The Mayo Clinic on Colonoscopy