Colon Cancer

How Is Colon Cancer Diagnosed?

If people experience symptoms like those of colorectal cancer, they need to make an appointment with their family physician, a gastroenterologist, a physician specially trained in the management of digestive system disorders, or a colon and rectal surgeon, a specialist in treatment of diseases of the colon.

The doctor performs a thorough clinical evaluation that includes:

  • A complete medical, family, and drug history
  • A physical examination, including a digital rectal examination

Tests that may be performed include:


A sigmoidoscopy is a specialized screening or diagnostic test for colorectal cancer. People age 50 and older who have no symptoms may have a sigmoidoscopy to check for suspicious areas inside the colon. Those who have symptoms, such as abdominal discomfort, persistent diarrhea, or blood in the stools, have this test to help determine the exact cause of these problems.

During this test:

  • A flexible viewing tube known as a sigmoidoscope is inserted through the anus and rectum and on through the lower part of the colon, called the sigmoid. A sigmoidoscope is a soft, flexible fiberoptic scope.
  • Doctors examine the inner walls of these areas to determine if disease is present. They look for tumors, polyps, inflammation, and other tissue changes that are associated with diseases of the anus, rectum, and sigmoid colon.
  • If doctors see an area of tissue in the colon that looks unusual or questionable, they remove a small sample of tissue, known as a biopsy.

The tissue sample is sent to a laboratory for analysis. A pathologist examines the biopsy tissue under a microscope. If the tissue is abnormal or appears normal but suspicious, the patient is scheduled for a colonoscopy.

A sigmoidoscopy may detect about 50 percent of colon tumors and nearly 100 percent of rectal tumors.

The benefits of a sigmoidoscopy include:

  • A direct view of the inner walls of the rectum and sigmoid colon
  • Ability to obtain a biopsy sample
  • Test is performed in the doctor’s office without the need for sedatives
  • There may be a sense of discomfort but usually no pain.


A colonoscopy is a screening and diagnostic procedure during which the inside walls of the entire colon are examined. The doctor uses an instrument called a colonoscope. This is a flexible fiber optic tube that bends around with the shape and turns of the colon. The colonoscope is typically attached to a video camera and monitor. This allows the doctor to clearly view the inside walls and lining of the colon.

A colonoscopy is used to diagnose conditions of the bowel, including:

  • Ulcerative colitis
  • Crohn’s disease
  • Diverticular disease such as diverticulosis
  • Polyps
  • Colon cancer

How-To Information:

When preparing to have a colonoscopy:

  • Do not eat on the day of the test.
  • Drink only clear liquids on the day before the test.
  • A special laxative is given the day before the test in order to cleanse the intestines.
  • An enema may be prescribed for the day of the test.

Antibiotics may be prescribed for people who have:

  • An artificial heart valve
  • Undergone joint replacement surgery
  • Taken preventive antibiotics before dental work.

Antibiotics help reduce the relatively small risk of infection associated with artificial components in the body.

Other Tips:

  • Don’t take anti-inflammatory drugs, such as aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen sodium for at least 10 days before the test. This helps minimize the possibility of excessive bleeding.
  • Arrange for a ride home after the colonoscopy.

During a colonoscopy,

  • The patient lies on his or her left side.
  • The doctor administers a sedative intravenously, to help the patient relax and not feel any discomfort.
  • After a rectal examination and lubrication of the anal area, the colonoscope is gently passed into the rectum and is slowly advanced along the colon.
  • A small amount of air is inserted into the colon to help keep the walls apart. The air fills the interior space of the colon and allows the instrument to move freely inside the colon.

If the doctors see polyps in the colon, it may be possible to remove them. Samples from the polyps are removed and sent to a laboratory for thorough examination.

A colonoscopy is similar to a sigmoidoscopy, but it is more extensive and may be preferred in some patients. Because polyps are sometimes removed during a colonoscopy, the procedure is diagnostic as well as therapeutic.

Need To Know:

Colonoscopy is a safe procedure, but it is not risk-free. On rare occasions, complications may occur, including

  • Infection
  • Bleeding
  • Accidental puncture or perforation in the area where the colonoscope passes

After the procedure, the doctor should be called immediately if the patient:

  • Does not feel well
  • Experiences excessive bleeding from the rectum
  • Has severe abdominal pain
  • Eliminates black stools; this may indicate the presence of bleeding
  • Develops a fever

Double Contrast Barium Enema (Barium Meal And Enema)

The double contrast barium enema, also called air contrast barium enema, is a special test that helps doctors diagnose diseases of the colon. Barium is a chemical substance that shows up on x-ray films. This allows doctors to see an outline of the colon on x-ray films.

During this test:

  • The bowel must be as empty as possible. The evening before the test, the patient takes a laxative. Liquid barium is inserted into the rectum through a small tube.
  • Numerous X-ray pictures of the intestine are taken and provide the radiologist a clear, outlined view of the entire colon.
  • A radiologist carefully examines the X-ray films and reports on any abnormalities.

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