What is a colonoscopy?

A colonoscopy is a procedure that examines the lining of your colon and rectum using a thin, flexible instrument called a colonoscope. The colonoscope has a camera that transmits pictures of the inside of your colon to a video screen.

The colon and the rectum make up the large intestine, sometimes called the large bowel. The large intestine is a long, hollow organ in your abdomen that plays an important role in digestion by removing water from digested material and forming feces.  

A colonoscopy is an important test that can detect colorectal cancer in its earliest, most curable stage. It also helps diagnose unexplained intestinal symptoms, such as changes in your bowel movements, abdominal pain, or rectal bleeding. 

Colonoscopy is only one method used to test for colon cancer. Discuss all the screening and testing options with your doctor to understand which options are right for you.

Types of colonoscopy

The types of colonoscopy procedures include:

  • Colonoscopy is an endoscopy procedure that involves inserting a colonoscope into the large intestine through the anus. The colonoscope contains a camera that transmits pictures of the inside of your colon to a video screen.
  • Virtual colonoscopy is a type of computerized tomography (CT) scan that uses X-rays to produce images of the inside of the large intestine. Despite its name, virtual colonoscopy is not an actual endoscopy procedure because it does not involve inserting a colonoscope into the large intestine. 

Other procedures that may be performed

Your doctor may perform other procedures in addition to colonoscopy to diagnose or treat certain conditions. These include:

  • Control of bleeding in the large intestine. This involves injecting medications, applying clips, or sealing bleeding vessels with heat
  • Removal of colon polyps, which are abnormal growths in the large intestine that can become cancerous
  • Tissue biopsy, which involves removing polyps or samples of abnormal looking intestinal tissues. Tissues are examined and tested in a lab for cancer and other diseases.

Why is a colonoscopy performed? 

Your doctor may recommend a colonoscopy to diagnose and treat diseases and conditions of the colon and rectum including:

  • Abdominal pain if the underlying cause has not been found through less invasive testing. Abdominal pain can be caused by many different conditions, such as inflammatory bowel disease, diverticulitis, and intestinal ulcer. 
  • Anemia (low red blood cell count) if the underlying cause has not been found through less invasive testing. A colonoscopy can be used to identify potential bleeding sites.
  • Bleeding symptoms, such as rectal bleeding, bloody stool, or black, tarry feces. Potential causes include colon cancer and intestinal inflammation or damage.
  • Bowel movement changes, such as pencil thin stools. Bowel movement changes are caused by various conditions, such as intestinal inflammation and colon cancer.
  • Colon polyps, abnormal growths in the large intestine that can become cancerous. In some cases, polyps are first identified during another procedure called a barium enema and removed during colonoscopy.
  • Colorectal cancer screening. A colonoscopy can identify and remove abnormal tissue and colon polyps before they develop into cancer.
  • Diarrhea. A colonoscopy can identify inflammation and infections.
  • Diverticulosis and diverticulitis, intestinal pockets that can develop over time and can become infected or cause bleeding
  • Inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease
  • Unexplained weight loss if the underlying cause has not been found through other, less invasive tests

Who performs a colonoscopy?

The following doctors commonly perform colonoscopies:

  • Gastroenterologists are internists who specialize in diseases of the intestines. Gastroenterologists perform most colonoscopies. 

Other doctors who perform colonoscopies: 

  • Colon and rectal surgeons are general surgeons with extra training in the surgical treatment of intestinal and rectal conditions.
  • General surgeons specialize in the surgical treatment of a variety of diseases, disorders and conditions. Some general surgeons focus their practice on the intestinal tract.