A colonic tissue culture is a laboratory test performed on a specimen of colon (large intestine) tissue to isolate and identify organisms that may be causing certain infections, such as infectious diarrhea or parasitic and viral infections involving the colon.

The specimen is obtained by a colonoscopy. A colonoscopy is a procedure for viewing the interior lining of the colon using a colonoscope, a flexible fiber-optic tube about 1/2 inch thick.

A sample of colon tissue is obtained during a colonoscopy procedure using special instruments. The specimen is sent to the laboratory and placed in special culture media. The specimen is incubated at different temperatures and examined daily for the presence of microorganisms.

If certain microorganisms are detected, the laboratory will perform additional testing to further classify them. Susceptibility testing of the microorganisms will help find the best antimicrobial therapy.

The preparation for the culture is the same as for a colonoscopy. The large intestine must be thoroughly cleansed. You may be asked to take laxatives or an enema the evening prior to the test. You will likely be instructed to be on a clear liquid diet for 24 to 48 hours before the test.

Before the colonoscopy is performed, the risks and benefits of the procedure will be explained to you, and you will be asked to sign a consent form. You may be given a sedative to help you relax as the colonoscopy is being done.

You may feel the urge to defecate when the colonoscope is inserted.

The culture is performed to detect and identify certain infections which can affect the colon, especially when other tests such as stool culture have been unable to identify the underlying infection.

A colonoscopy may also be performed for other reasons, such as to identify certain forms of cancer or inflammatory bowel disease.

The colon has a high number of well-characterized bacteria termed "bowel flora." The growth of these organisms in culture from a colonic biopsy does not mean there is an infection. These organisms are part of the normal flora present in the gut.

The detection of certain organisms in a colonic biopsy culture is considered abnormal. This includes certain bacteria, such as salmonella, shigella, Clostridium difficile, Mycobacterium tuberculosis and others. Parasites such as schistosomiasis and viruses such as cytomegalovirus are other examples of pathogenic organisms that may be detected.

A colonoscopy is usually a safe procedure. However, it can cause a perforation (hole) in the large intestine, infection, and bleeding.

After the colonoscopy, you may have large amounts of flatulence (gas) caused by the air used to distend the colon.