What is a
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
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
What can I expect after
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
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.