Standard tests used for detecting colon cancer include

Fecal Occult Blood Test (FOBT).

Flexible Sigmoidoscopy.

Colonoscopy.

Double contrast Barium enema.

Digital Rectal Exam (DRE).

Digital Rectal Exam (DRE) here a doctor examines the rectum with the gloved end of a finger. A DRE is often included as part of a routine physical exam. This simple test, which is not usually painful, can detect any growth in the anal canal or lower rectum.

Fecal Occult Blood Test (FOBT) is used to detect tiny amounts of invisible blood in the feces. Blood vessels at the surface of colorectal polyps or cancers are often fragile and easily damaged by the passage of feces. The damaged vessels usually release a small amount of blood into the feces. Only rarely is there enough bleeding to color the stool red. The FOBT detects blood through a chemical reaction.

Immunochemical Fecal Occult Blood Test (iFOBT) is a new test, which helps to detect hidden blood in the stools. It is more specific than the FOBT and reduces the number of false positive results.

Flexible Sigmoidoscopy is a test, which allows the physician to look directly at the lining of the lower colon and rectum with the help of a lighted instrument called a Sigmoidoscope. This test allows the physician to look for early signs of colorectal cancer like bleeding and polyps.

Colonoscopy allows the physician to visualize the entire colon and rectum using an instrument called Colonoscope. Here a long flexible tube with a light is inserted through the rectum. The Colonoscope is also connected to a video camera and display monitor so the doctor can see and closely examine the inside of the colon.

Biopsy: Usually if a suspected colorectal cancer is found by any diagnostic test, it is biopsied during Colonoscopy. In a biopsy, the doctor removes a small piece of tissue with a special instrument passed through the scope. The biopsy specimen is sent to the pathology laboratory where a pathologist, a doctor trained to diagnose cancer and other diseases in tissue samples, examines the tissue under a microscope.

Double contrast Barium enema consists of a series of x-rays of the entire colon and rectum. ‘Double contrast’ refers to the use of both barium and air to outline the lining of the colon. The x-rays are taken after the patient is given an enema with a barium solution and air is introduced into the colon. This procedure helps to outline large polyps and cancers.

Two new tests

Researchers are working on less-invasive screening technologies that may be better tolerated and more accepted. Two emerging screening methods are:

DNA stool testing. By examining a sample of the stool for cellular markers, this test can reveal the presence of colon cancer as well as precancerous polyps.

Virtual Colonoscopy (CT colonography). This technology uses data from a conventional CT scan to create three-dimensional images of the interior of the colon, allowing the doctor to detect abnormal growths without inserting a Colonoscope.