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Bowel Preparation

Definition, Purpose, Precautions, Description, Preparation, Aftercare, Risks, Normal results, Abnormal results

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


The ultimate goal of bowel preparation is priming the bowel for a diagnosis 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 visualization of 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 colon/rectal 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 studies that showed an abnormality
  • removal of polyps
  • biopsy
  • evaluation of chronic diarrhea or inflammatory bowel disease
  • to detect recurrences for colon/rectal 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 procedures such as barium enema (introducing a barium containing chemical to promote better visualization of intestines during x rays) or colonoscopy. Preparation of the bowel distally—from the rectum—is necessary for diagnostic procedures such as sigmoidoscopy. Prior to surgical procedures bowel preparation is recommended to decrease the possibility of developing more medical problems. Patients may also be given a course of antibiotics to prevent the possibility of infection.


Bowel preparation for visualization of the colon is performed to ensure the procedure will be accurate and complete. There are several effective cleansing preparations that include: Polyethylene glycol solution, 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.


After the preparation has been ingested the patient is advised to only ingest clear liquids until midnight.


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

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.



Pfenninger, John L., et al. Procedures for Primary Care Physicians. 1994.

Tierney, Lawrence M., et al, eds. Current Medical Diagnosis and Treatment 2001. 40th ed. MCGraw-Hill, 2001.


Sturmann, K. "Neurologic Emergencies: The Neurologic Examination." Emergency Medicine Clinics of North America 15 (Aug. 1997).


American College of Gastroenterology. 4900 B South 31st Street, Arlington, VA 22206. (703) 820-7400. <http://www.acg.gi.org/ct_html>.

Laith Farid Gulli, M.D.

Bilal Nasser, M.Sc.


Lesion—An abnormal change in tissues.

Polyp—A growing mass of tissue.

Additional topics

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