Colonoscopy is a minimally invasive endoscopic procedure that lets your doctor examine the lining of your large intestine (colon) for abnormalities. During colonoscopy, your doctor inserts a thin, flexible tube into your rectum and slowly moves it through the entire length of the colon. This instrument, called a colonoscope, has a camera and light source and allows your doctor to look at the lining of your colon and rectum.
Colorectal cancer (cancer of the colon or rectum) is the second leading cause of cancer deaths in the United States. Every year, around 153,000 new cases of colorectal cancer are diagnosed. Roughly 53,000 people die from the disease each year in the United States. To put this into perspective, 1 in 22 men and 1 in 24 women will be diagnosed with colorectal cancer in their lifetime.
It has been estimated that increased awareness and screening for colorectal cancer would save at least 30,000 lives each year. Most individuals are considered “average risk” for developing colorectal cancer during their life. For this group of people, screening for colorectal cancer is now recommended to start at age 45. When individuals are at higher risk due to their family history or certain genetic conditions, screening should also begin sooner.
Colonoscopy may also be recommended by your doctor to evaluate for symptoms such as bleeding, abdominal pain, and chronic diarrhea. This is not a “screening colonoscopy,” but referred to as a “diagnostic colonoscopy” exam. Furthermore, a “surveillance colonoscopy” is an exam performed when you have had polyps removed in the past.
There are many different methods that can be used for colorectal cancer screening. You may have heard about alternatives to colonoscopy, such as stool tests and CT scans, also known as “virtual” colonoscopy. Although these tests have some benefits, colonoscopy is the single best screening test for colorectal cancer because it is still the only test that can (1) detect polyps which are pre- cancerous growths that may develop into colorectal cancer, and (2) directly prevent colorectal cancer by removing these polyps. No other test has these advantages. For patients, this is an important benefit because once colorectal cancer has developed, it can no longer be removed with colonoscopy and requires more invasive treatments such as surgery and/or chemotherapy. Also, if a stool test or CT scan shows something abnormal within the colon, a colonoscopy would still be needed in order to further investigate the abnormality.
Before a colonoscopy, your doctor will explain how to change your diet and how to start your bowel preparation. You will also be instructed when to start fasting. In general, you will be on a clear liquid diet the day before the exam. Your doctor will also instruct you to consume a solution that will empty and clean your colon before the exam. This is called a bowel preparation, or bowel prep – this is the hardest part of the colonoscopy but also one of the most important! A clean and empty colon allows the physician to see more clearly; a dirty colon may result in an incomplete or partial examination, and more difficulty in detecting polyps.
Before your exam, most medications can be continued as usual. However, some medications can interfere with the bowel preparation or with the safety of the procedure. Tell your doctor about any medications you are taking, particularly insulin or other diabetes medications, aspirin products, arthritis medications, blood thinners (such as warfarin, apixaban, rivaroxaban, heparin, etc.), and other drugs that interfere with clotting (such as clopidogrel (Plavix), ticagrelor, prasugrel, etc.). Over-the-counter medications and supplements should not be taken the morning of the procedure. Let your doctor know about any medical conditions you have, such as heart, kidney or lung disease. Also, be sure to mention any allergies you have to medications or latex. Follow your doctor’s instructions carefully to ensure a successful procedure.
Immediately before the procedure, you may receive medications to help you relax, make you sleepy and to minimize discomfort. You might feel abdominal pressure, bloating or cramping during the procedure. Depending on your doctor’s practice setting, the procedure may be done with certain types of anesthesia that allow you to be completely asleep for the entire length of the colonoscopy exam.
You will lie on your left side or back during the exam. Your doctor will pass a long, flexible tube with a camera (a colonoscope) along the entire length of the large intestine (colon) and rectum in order to carefully examine the lining. The examination usually takes about 30 minutes. In rare cases, the doctor may not be able to move the colonoscope through the entire colon. If this happens, your doctor will tell you if any additional testing is necessary.
During the exam, if your doctor sees something that needs more evaluation, a small instrument may be passed through the colonoscope to obtain a biopsy (tissue sample). Your doctor may find growths in the colon, called polyps. Because most polyps are pre- cancerous (but still benign), they will most likely be removed during the examination.
When a colonoscopy is being performed to look for sites of bleeding, the doctor might control bleeding by injecting medications, or by sealing off bleeding vessels with heat treatment (called cauterization), or by applying small metal clips. These procedures usually do not cause any pain.
You will be sent home after the procedure when most of the effects of the medications have worn off. Someone must accompany you home from the procedure because of the medications used during the examination. You should not drive, operate machinery, or make legal decisions the day of the procedure to make sure that the effects of the medication have worn off. Even if you feel alert after the procedure, the medications can affect your judgment and reflexes for the rest of the day.
Some patients experience mild discomfort, bloating, or pass gas because of the air introduced during the examination. Those symptoms usually resolve within a day. You can resume your usual diet unless you are instructed otherwise. Your doctor generally can inform you of the preliminary results of the procedure that day, but the results of some tests, including biopsies, may take several days to return.
(1) how clean was your colon and whether your doctor was able to examine everything
(2) how many pre-cancerous polyps you had that were removed
(3) the size of the largest polyp
(4) whether any polyps had serious features such as an early cancer.
Based on these factors, your doctor will give you instructions on when to return for your next colonoscopy (i.e. 10 years, 5 years, 3 years, etc.).
Colonoscopy is a common outpatient procedure. It does not require hospitalization. Complications from a colonoscopy are rare, but they can occur. Perforation (a hole or tear in the gastrointestinal tract lining), is very rare, but can occur and may require emergency surgery. If a biopsy is taken or if a polyp is removed, the area may bleed, but it is usually minor. Bleeding usually stops on its own, but sometimes
it requires treatment. Some patients might have a change in heart rate, blood pressure or breathing from the medications. Although complications after a colonoscopy are uncommon, it is important to recognize their early signs. Contact your doctor right away if you have a fever after the test or notice increasing abdominal pain, or bleeding, including black stools. If you have any concerns about a possible complication, it is always best to contact your doctor right away.
It is extremely important that your colon be thoroughly cleaned before your colonoscopy. This will let the doctor see any abnormalities, such as colon polyps, during the procedure. Polyps are small growths in the colon that could later turn into cancer. Cleansing the colon before a colonoscopy is called bowel preparation, or “prep.” It involves taking medication that causes diarrhea, emptying the colon. The medication is taken by mouth, and comes in liquid or tablet form. You will also need to change what you eat during the day or two before the colonoscopy.
Most bowel preparations involve drinking some prep liquid at two different times. The best way to cleanse the colon is with a “split-dose” bowel preparation. This involves drinking the first portion of the liquid preparation the evening prior to the colonoscopy, and then drinking the second part of the liquid preparation on the day of the colonoscopy. If your colonoscopy is scheduled to start in the morning, you must wake up early in the morning on the day of the colonoscopy to drink the second part of the prep. This can be an inconvenience for some people, but it gives your doctor the best chance of finding polyps or cancers in your colon. Taking both portions of the bowel preparation the evening prior to the colonoscopy, instead of taking the second portion of the prep on the morning of your colonoscopy, is an alternative option for cleansing the bowel. However, studies have shown that taking at least half of the prep solution on the same day as the colonoscopy provides the best bowel cleansing, which improves your doctors ability to find polyps and cancers in your colon. You should not drink any liquids (not even prep solution) within 2-3 hours of your colonoscopy. It is important that you understand the prep instructions given to you by your doctor, which will provide instructions on when you should drink your bowel prep.
Your doctor will prescribe the type of bowel prep that is best for you. You will receive specific instructions. In general, here is what you can expect:
Many patients feel that the bowel prep is the most difficult part of a colonoscopy. It is important that you try your best to fully complete the prep. After taking the entire bowel prep, you should be passing liquid that is watery or yellow and clear enough to see through. Your bowel must be clean so that your doctor can thoroughly examine your colon and not miss precancerous growths called polyps. If your colon is inadequately cleansed, your doctor may recommend repeating a colonoscopy sooner than if your colon had been properly cleansed.
Several types of bowel prep medications are available. Your physician will recommend which prep you should take. You will need to carefully follow your doctor’s instructions about the exact dose and timing of your prep. Some types of prep may be covered by your medical insurance. You’ll want to find out if you have any out-of-pocket costs.
Your medical condition is the most important factor in deciding which type of bowel prep is best for you. It is best to share your complete medical history with your doctor. Also, tell your doctor if you are pregnant or breast feeding, or if you have a history of bowel obstruction. Let the doctor know if you have diabetes, high blood pressure, heart, kidney or liver disease, or if you have had any of these diseases in the past. You need to mention any allergies you have to medications to the doctor.
If you have had difficulty with a bowel prep in the past, be sure to mention this as well. Other factors in choosing the type of prep are the time of the colonoscopy appointment, individual preferences (taste and amount of medication), and out-of-pocket costs.
Call your doctor and ask what to do if you are not able to complete the bowel prep as advised. The procedure might need to be canceled and rescheduled.
You should expect to have multiple loose bowel movements with minimal discomfort while doing the prep. However, some people will have nausea, vomiting, bloating (swelling in the abdomen) or abdominal pain. Serious side effects are uncommon. Your doctor will explain the possible side effects of the prep selected for you.
This information was developed by the Publications Committee of the American Society for Gastrointestinal Endoscopy (ASGE). This information is the opinion of and provided by the American Society for Gastrointestinal Endoscopy. For more information about ASGE, visit www.asge.org. This information is intended only to provide general guidance. It does not provide definitive medical advice. It is important that you consult your doctor about your specific condition.
