What Is a Colonoscopy?
A colonoscopy is both a diagnostic and therapeutic procedure used to examine and treat the rectum, colon, and a portion of the terminal ileum.
A colonoscopy is performed with a colonoscope, which is a flexible and steerable instrument used to evaluate the entire colon (large intestine).
What Is a Colonoscopy Used For?
A colonoscopy is routinely used to screen for colon and rectal cancer. Screening for colorectal cancer is generally recommended for healthy adults with no risk factors starting at age 50.
Risk factors for colorectal cancer include:
- Male gender
- African-American ethnicity
- Family history of polyps or colorectal cancer
- Personal history of inflammatory bowel disease (IBD), such as ulcerative colitis and Crohn’s disease
- Lynch syndrome, or another genetic disorder that increases the risk of colorectal cancer
- Being overweight/obese
Colonoscopies are also used to diagnose gastrointestinal (GI) disorders such as:
- Colon cancer
- Colon polyps
- Inflammatory bowel disease (IBD)
Colonoscopy is also used to help determine the cause of:
- Gastrointestinal bleeding
- Rectal bleeding
- Changes in bowel habits, including diarrhea
- Abdominal pain
- Abnormal X-rays or computerized tomography (CT) scans
- Unexplained weight loss
A colonoscopy can also be used to provide therapy and treatment such as:
- Removal of polyps
- Control of bleeding
How Do Patients Prepare for a Colonoscopy?
Prior to a colonoscopy, patients are given “bowel prep” instructions to follow at home before the procedure to clear out the intestine. The bowel prep will cause diarrhea, and patients are advised to stay close to a bathroom. Bowel prep can be unpleasant and many patients find this worse than the actual procedure, but it is very important to clear the bowels so the doctor can visualize the lining of the colon.
- Patients are advised to follow a clear liquid diet for 1 to 3 days before the procedure, such as:
- Fat-free bouillon or broth
- Gelatin in flavors such as lemon, lime, or orange (avoid red and purple-colored drinks or gelatin)
- Sports drinks in flavors such as lemon, lime, or orange
- Plain coffee or tea, without cream or milk
- Strained fruit juice, such as apple or white grape (avoid orange juice)
- Laxatives are also prescribed
- There are different combinations of laxatives that may be prescribed
- Patients usually need to drink a large amount – often a gallon -- of liquid laxative the night before and morning of the procedure
- An enema may be prescribed
How Do Doctors Perform a Colonoscopy?
A colonoscopy is usually performed by a specialist in the digestive tract called a gastroenterologist. The procedure is typically done in a hospital or an outpatient center and takes about 30 to 60 minutes.
- Sedatives, anesthesia, or pain medicine is administered intravenously (IV)
- The patient lies on a table and the doctor inserts a colonoscope through the anus and into the rectum and colon
- The scope inflates the large intestine (colon) with air for a better view, and the camera sends a video image to a monitor, allowing the doctor to examine the large intestine
- If polyps are found, they may be removed
- A biopsy may be performed if abnormal tissue is found
- The tube is withdrawn when the procedure is complete
After a colonoscopy:
- The patient remains at the hospital or outpatient center for 1 to 2 hours after the procedure to allow the anesthesia to wear off
- Patients should have an arranged ride home since they will not be able to drive immediately following the procedure
- Patients are able to return to a normal diet by the next day
How Painful Is a Colonoscopy?
Colonoscopies are usually not painful, and patients generally do not feel anything at all. Most colonoscopies are performed using “intravenous sedation” or “twilight sedation” in which patients are drowsy, but comfortable and still breathing on their own. The most common type of sedative used for a colonoscopy also has a mild amnesiac effect, and most patients do not even remember the procedure.
Patients may experience abdominal cramping or bloating shortly after the procedure, and if polyps were removed or a biopsy was taken there may be light bleeding from the anus.
What Are Risks and Complications of a Colonoscopy?
Colonoscopy is generally a very safe procedure and complications are rare. Complications of a colonoscopy may include:
- Cardiac and respiratory problems related to a reaction to the sedative
- Colon perforation that may require surgery
- Bleeding from polyp removal or from the procedure itself, which may require additional treatment such as hospitalization and/or blood transfusions
- Severe abdominal pain
- Death (rare)
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