A colonoscopy is an exam of the lower part of the gastrointestinal tract, which is called the colon or large intestine (bowel). Colonoscopy is a safe procedure that provides information other tests may not be able to give. Patients who require colonoscopy often have questions and concerns about the procedure.
Colonoscopy is performed by inserting a device called a colonoscope into the anus and advancing through the entire colon. The procedure generally takes between 20 minutes and one hour.
The most common reasons for colonoscopy are:
- To screen for colon polyps (growths of tissue in the colon) or colon cancer
- Rectal bleeding
- A change in bowel habits, like persistent diarrhea
- Iron deficiency anemia (a decrease in blood count due to loss of iron)
- A family history of colon cancer
- A personal history of colon polyps or colon cancer
- Chronic, unexplained abdominal or rectal pain
- An abnormal x-ray exam, like a barium enema or CT scan
Before colonoscopy, your colon must be completely cleaned out so that the doctor can see any abnormal areas. This is vitally important to increase the chances that your doctor will identify abnormalities in your colon. If your colon is not completely cleaned out, the chances your doctor will miss abnormalities increases. Your doctor's office will provide specific instructions about how you should prepare for your colonoscopy. Be sure to read these instructions as soon as you get them so you will know how to take the preparation and whether you need to make any changes to your medications or diet. If you have questions, call the doctor's office in advance.
You will need to avoid solid food for at least one day before the test. You should also drink plenty of fluids on the day before the test. You can drink clear liquids (a liquid you can hold up to the light and see through) up to several hours before your procedure, including:
- Clear broth (beef, chicken, or vegetable)
- Coffee or tea (without milk)
- Gelatin such as Jell-o (avoid red gelatin)
Avoid drinking red liquids. Your doctor may also ask you to avoid high fiber foods including seeds and nuts for the week before the procedure.
A commonly used preparation is a 4-liter (1 gallon) solution that is purchased at the pharmacy with a prescription. Refrigerating the solution can make it easier to drink, but do not put ice in the solution since it will melt and you will have to drink even more fluid. Drinking this solution may be the most unpleasant part of the exam. Watery diarrhea is the desired result. This may occur shortly after drinking the solution or may be delayed for several hours. The end result should be diarrhea that looks like urine. If you become nauseated or vomit while drinking the solution, call your doctor or nurse for instructions. Tips that can help with nausea and vomiting include temporarily stopping drinking the solution, walking around, and resuming drinking at a slower pace.
Before the test, a doctor will review the procedure with you, including possible complications, and ask you to sign a consent form. An IV line will be inserted in your hand or arm. Your blood pressure, heart rate, and breathing will be monitored during the test.
You will be given fluid and medicines through the IV line. With sedation/analgesia provided by the doctor, many people sleep during the test, while others are very relaxed, comfortable, and generally not aware. Your doctor may request an anesthesiologist give you an anesthetic agent (for example, propofol), which is a stronger sedative and will put you to sleep while you are being closely monitored.
The colonoscope is a long black flexible tube, approximately the diameter of the index finger. The doctor will gently pump air and sterile water or saline through the scope into the colon to inflate it and allow the doctor to see the entire lining. You might feel bloating or gas cramps as the air opens the colon. Try not to be embarrassed about passing this gas (it is just air), and let your doctor know if you are uncomfortable.
During the procedure, the doctor might take a biopsy (small pieces of tissue) or remove polyps. Polyps are growths of tissue that can range in size from the tip of a pen to several inches. Most polyps are benign (not cancerous). However, some polyps can become cancerous if allowed to grow for a long time. Having a polyp removed does not hurt.
After the colonoscopy, you will be observed in a recovery area, usually for about 30 to 60 minutes until the effects of the sedative medication wear off. The most common complaint after colonoscopy is a feeling of bloating and gas cramps. You should pass gas and not feel embarrassed doing this either during or after the procedure. This will relieve your feelings of bloating and cramping. You may also feel groggy from the sedation medications. You should not return to work, drive, or drink alcohol that day. Most people are able to eat normally after the test. Ask your doctor when it is safe to restart aspirin and other blood-thinning medications.
Colonoscopy is a safe procedure, and complications are rare but can occur:
- Bleeding can occur from biopsies or the removal of polyps, but it is usually minimal and can be controlled.
- The colonoscope can cause a tear or hole in the colon. This is a serious problem, but it does not happen commonly.
- It is possible to have side effects from the sedative medicines.
- Although colonoscopy is the best test to examine the colon, it is possible for even the most skilled doctors to miss or overlook an abnormal area in the colon.
- You should call your doctor immediately if you have any of the following:
- Severe abdominal pain (not just gas cramps)
- A firm, bloated abdomen
- Rectal bleeding (greater than a couple of tablespoons [30 mL])
Although many people worry about being uncomfortable during a colonoscopy, most people tolerate it very well and feel fine when the procedure is complete. It is normal to feel tired, so plan to take it easy and relax the rest of the day.
Your doctor can describe the results of the colonoscopy as soon as it is over. If s/he took biopsies or removed polyps, you should call for results within one to two weeks if your doctor has not already contacted you.