Bowel Preparation

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Bowel Preparation


Bowel preparation is a procedure usually undertaken before a diagnostic procedure or treatment can be initiated for certain colorectal diseases. Bowel preparation is a cleansing of the intestines from fecal matter and secretions.


The ultimate goal of bowel preparation is to empty and cleanse the bowel for a diagnostic procedure (using x rays to detect a disease process in the intestines) or for surgical intervention (such as removal of polyps, cancer, or narrowing of the intestinal diameter). Colonoscopy is an effective treatment procedure for polyps (a growing mass of tissue). This procedure enables the doctor to visualize the entire large bowel. During a colonoscopy, polyps can be cauterized (applying an electric current which incinerates the polyp). The procedure can be both diagnostic and therapeutic. A sigmoidoscopy scope is a flexible tube that allows clinicians to view the sigmoid colon (the part of the large intestine before the rectum). This procedure is important for detection of colorectal cancer. It is safe, quick to perform (usually 30-45 minutes in about 90% of cases), and an effective diagnostic tool for evaluation of:

  • rectal bleeding
  • other abnormalities detected by imaging studies
  • removal of polyps
  • biopsy
  • evaluation of chronic diarrhea or inflammatory bowel disease
  • recurrences of colorectal cancer or polyps
  • relieving a twisted bowel
  • foreign body removal
  • treating bleeding lesions
  • preventive surveillance of cancer in patients with a positive family history of colon cancer


Antibiotic prophylaxis is not routinely recommended. In some cases of prosthetic heart valves, antibiotics can be prescribed. Evidence exists that evacuation of intestinal waste products in conjunction with antibiotics before (prophylactic) the procedure reduces the possibility of sepsis (infection which spreads from the primary site to blood).


The bowel is emptied of any contents for such procedures as barium enema (introducing a compound containing barium to promote better visualization of intestines during x rays) or colonoscopy. Preparation of the bowel distallyfrom the rectumis necessary for such diagnostic procedures as sigmoidoscopy. Bowel emptying is done through taking oral laxative solutions that speed up the excretion of the contents of the lower bowel together with restrictions on solid food intake.

A newer type of imaging study may eventually make current laxative methods of bowel preparation obsolete. According to a group of researchers in the United Kingdom, computed tomography (CT) colonography (sometimes called virtual colonoscopy) has shown itself to be as accurate in diagnosing colorectal tumors as optical colonoscopy. CT colonography allows a radiologist to examine the colon and nearby organs in less than 30 seconds.


Lesion An abnormal change in tissues.

Polyp A growing mass of tissue.


Bowel preparation for visualization of the colon is performed to ensure the procedure will be accurate and complete. There are several effective cleansing preparations including polyethylene glycol solution (Colyte), sodium phosphate solution (Phospho-Soda), magnesium citrate with bisacodyl tablets, and castor oil with bisacodyl tablets. One of these preparations should be administered starting at 4:00 p.m. the day before the procedure. Patients are usually asked to avoid solid foods for about 36 hours before diagnostic procedures. Such clear liquids as vegetable or beef broth, apple or white grape juice, soda pop or fruit-flavored gelatin are permitted, although some doctors ask patients to avoid red-colored beverages or gelatin flavors on the grounds that the red food coloring in these products may make bleeding more difficult to detect.

In most cases, patients may continue to take other prescription medications at the usual times while they are restricted to clear liquids. It is a good idea, however, to check with the doctor beforehand.


Patients should have a friend or relative to drive them home after the procedure, as the combination of a period of dietary restriction, frequent bowel movements, and the procedure itself leaves most people feeling tired and slightly weak. Many doctors advise patients to postpone vigorous physical activity or work requiring mental concentration until the day after the procedure. Patients can resume eating solid foods as soon as they get home.

Some patients may notice a small amount of blood on toilet tissue or underwear following a colonoscopy or other examination of the lower digestive tract. Spotting is not cause for concern; however, patients who have steady or heavy bleeding from the rectum should call their doctor as soon as possible.


The current standard of care dictates that patients receive antibiotic prophylaxis if they are at increased risk of developing an infection. High-risk patients include those with cardiac diseases or patients with prostheses.

Bowel preparation can be stressful for some patients, particularly those with pre-existing nutritional problems associated with cancer treatment or malabsorption. In addition, many patients find the various oral solutions unpleasant to the taste and difficult to swallow for that reason. According to one British study, oral solutions flavored with lemon are more acceptable to patients than unflavored forms. Both Colyte and Phospho-Soda are available with flavoring added; patients may wish to ask their pharmacist for these specific products. Mild nausea, vomiting, stomach cramps, intestinal gas, dry mouth, and increased thirst are common side effects of these products. Some patients are helped by taking an electrolyte supplement along with oral sodium phosphate solution to lower the risk of dehydration.

Some people may have severe allergic reactions to commonly used oral laxatives used for bowel preparation. Patients who develop hives, swelling of the face or hands, swelling or tingling in the throat or mouth, difficulty breathing, or tightness in the chest should call their doctor at once. This type of reaction is a medical emergency.

Normal results

Absence of anatomical changes or abnormalities in the intestines would result in normal diagnosis.

Abnormal results

Polyps can be treated with electrocautery. A biopsy is taken of any suspicious polyps and further analyzed. Sigmoidoscopy can detect masses, bleeding, and ulcerative disease.



Tierney, Lawrence M., et al, editors. Current Medical Diagnosis and Treatment 2001. 40th ed. New York: McGraw-Hill, 2001.

Wilson, Billie A., Margaret T. Shannon, and Carolyn L. Stang. Nurses Drug Guide 2000. Stamford, CT: Appleton & Lange, 2000.


Bulmer, Frances M. "Bowel Preparation for Rectal and Colonic Investigation." Nursing Standard 14 (February 2000): 32-35.

Burling, D., S. Taylor, and S. Halligan. "Computerized Tomography Colonography." Expert Review of Anticancer Therapy 4 (August 2004): 615-625.

Tjandra, J. J., and P. Tagkalidis. "Carbohydrate-Electrolyte (E-Lyte) Solution Enhances Bowel Preparation with Oral Fleet Phospho-Soda." Diseases of the Colon and Rectum 47 (July 2004): 1181-1186.


American College of Gastroenterology. 4900 B South 31st Street, Arlington, VA 22206. (703) 820-7400.

American Society of Health-System Pharmacists (ASHP). 7272 Wisconsin Avenue, Bethesda, MD 20814. (301) 657-3000.

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA.

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Bowel Preparation

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