Diagnosis of Colon Cancer

The diagnosis should usually be confirmed by biopsy in which a small (2mm diameter) sample of tissue is taken painlessly with forceps inserted through a small tube (a proctoscope or sigmoidoscope).

To spot cancers further along the colon, the doctor will use either a flexible sigmoidoscope (to see the part of the colon nearest the rectum, including the sigmoid [bendy] colon on the left side of the abdomen) or a colonoscope (to see the whole colon, including the part on the right side of the abdomen).

Colonoscopy is usually performed using intravenous sedation and takes about 30 minutes. Flexible sigmoidoscopy takes about 10 minutes and can usually be done without sedation.

Alternatively, a barium enema examination may be used to look at the whole colon. In this test, a liquid suspension of barium sulphate, which shows up on X-rays, is poured into the rectum through a narrow tube inserted through the anus. Usually a small balloon is then inflated in the rectum to pump in a small amount of air. This gives 'double contrast' to show the lining of the Colon in good detail. The procedure takes about 30 minutes.

For both procedures, the colon needs to be cleared by quite vigorous purgation (medicines are given to stimulate the intestines and clear out the Colon), which many patients find the most unpleasant aspect of the procedure.

Diagnosis involves screening to detect colorectal cancer in asymptomatic patients (i.e., those without symptoms) with no family history of the disease. Screening is recommended beginning at age 50 and includes the following:

Digital rectal examination (DRE) and fecal occult blood test annually and

Double-contrast barium enema every 5 10 years and

Flexible sigmoidoscopy every 5 years, or

Total colonoscopy every 10 years

Diagnosis of colorectal cancer in symptomatic patients and high-risk patients includes laboratory and imaging tests. Biopsy (i.e., removal of a tissue sample for examination under a microscope) is necessary to confirm the diagnosis.

In digital rectal examination (DRE), the physician inserts a lubricated, gloved finger into the patients rectum to feel for tumors. Approximately 510% of colorectal cancers are palpable (i.e., able to be felt).

Fecal occult blood test is used to detect microscopic blood in the stool, which may indicate early colorectal cancer. When results of this test are positive, the diagnosis is confirmed using additional procedures (e.g., barium enema, sigmoidoscopy, colonoscopy).

When colorectal cancer is suspected, laboratory tests such as urinalysis, blood tests (e.g., carcinoembryonic antigen level, complete blood count, electrolyte and chemical panels), and imaging tests are performed.

Imaging Tests
Imaging tests include the following:

Chest x-ray (used to detect cancer that has metastasized [spread] to the lungs)

CT scan (computerized tomography) (used to detect metastasis to lymph nodes, liver, or lungs)

Double-contrast barium enema (used to detect tumors throughout the colon)

Flexible sigmoidoscopy (used to detect tumors in the sigmoid colon and the rectum)

Total colonoscopy (used to detect tumors throughout the colon)

In double-contrast barium enema, air and a contrast solution (barium) are introduced into the large intestine and a fluoroscope is used to produce real-time images of the size, shape, and movement of the colon and rectum.

Patients must refrain from eating or drinking anything after midnight on the day of the procedure. They also are given a laxative and a cleansing enema before the procedure to make sure that the colon is empty.

Double-contrast barium enema results in an accurate diagnosis in about 90% of cases. It is less effective in patients with severe diverticulosis (i.e., condition in which many small pouches in the colon bulge outward).

Flexible sigmoidoscopy allows the physician to look for early signs of colorectal cancer (e.g., bleeding, polyps) in the lining of the sigmoid colon and rectum. In this test, a flexible tube containing a light and a camera (called a sigmoidoscope) is inserted through the anus into the rectum and sigmoid colon. The sigmoidoscope is used to transmit images to a monitor. If suspicious tissue is found, the physician inserts special instruments through the tube to remove a sample for examination under a microscope (called biopsy).

Patients must adhere to a liquid diet for 1224 hours before undergoing sigmoidoscopy to ensure that the colon is empty. The procedure usually takes 10 to 20 minutes and complications (e.g., bleeding, puncture of the colon) are rare.

Total colonoscopy allows the physician to view images of the entire colon and rectum using a long flexible tube with a light and camera (called a colonoscope). Biopsy of suspicious tissue can be performed using instruments inserted through the tube.

Colonoscopy patients must adhere to a liquid diet for 13 days before the procedure to ensure that the colon is completely empty. Patients are given a sedative and pain reliever before undergoing the procedure.

Colonoscopy usually takes 30 to 60 minutes and complications (e.g., bleeding, puncture of the colon) are rare. Medication or a probe (e.g., laser, heat, electric) can be inserted through the colonoscope to stop the bleeding if necessary.

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