Understanding Colonoscopy

What is a colonoscopy?

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.

Why is it important to be screened for colorectal cancer with colonoscopy?

Colorectal cancer (cancer of the colon or rectum) is the second leading cause of cancer deaths in the United States. Every year, around 145,000 new cases of colorectal cancer are diagnosed. Roughly 52,000 people die from the disease each year. 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 traditionally recommended to start at age 50. African American patients, however, are higher risk for developing colorectal cancer, and should begin screening at age 45. In addition, younger patients are increasingly being diagnosed with colorectal cancer, and some organizations such as the American Cancer Society have now recommended ALL patients start screening as early as age 45. When individuals are at higher risk due to their family history or certain genetic conditions, it usually begins 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.

Why is colonoscopy recommended?

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 precancerous 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.

What preparations are required before colonoscopy?

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.

What can I expect during a colonoscopy?

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.

What if the colonoscopy shows something abnormal?

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 precancerous (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.

What are polyps and why are they removed?

Polyps are abnormal growths in the colon lining that are usually benign (not cancer). Polyps can be commonly found by a colonoscopy (FIGURE 2). They grow in different shapes and sizes, and some of them have the potential to be pre-cancerous (but still benign) and can one day become colorectal cancer. Your doctor will remove polyps to determine if they are benign or malignant (cancer). Because polyps can be pre-cancerous, removing them is one of the major advantages of colonoscopy over other colorectal cancer screening tests, and an important way to prevent colorectal cancer.

How are polyps removed?

Your doctor will remove polyps with wire loops called snares or with biopsy instruments. Large polyps may require a referral to another doctor who specializes in removing them.

What can I expect after a colonoscopy?

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.

How often you need a colonoscopy depends on multiple factors: (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, and (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.).

What are the possible complications of colonoscopy?

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.

Important Reminder: This information is intended only to provide general guidance. It does not provide definitive medical advice. It is very important that you consult your doctor about your specific condition.