Sigmoidoscopy

Before your sigmoidoscopy

If you normally take prescription medicines, ask your healthcare team how to manage them before your test.

• To lower the risk of bleeding, you might need to stop taking aspirin or other blood-thinning medicines several days before the test.
• Your healthcare team might also ask you to adjust some medicines, such as those for diabetes. 
• You might need to stop other medicines, such as iron.

Eating and drinking before the test

Your healthcare team will tell you what you can eat and drink in the days leading up to the test.

It is very important to follow their instructions. Failing to do so might affect the procedure or the test results.

In general, you may be asked:

• For a few days before the test: Eat a low-fiber diet by avoiding foods like nuts, whole grains, raw fruits, and raw vegetables. This will make bowel prep easier.
• One day before the test: Drink only clear liquids such as broth, black coffee, gelatin, and clear juice.
• In the hours before the test: Stop eating or drinking anything, even water. Your healthcare team will set the exact time you need to stop.

Making a transportation plan

If you get a sedative to help keep you comfortable during the test, you will need to arrange for a ride home.

You might be sleepy or dizzy after the test and need someone to help you get safely into your home, so a cab or a rideshare service might not be a good option. Most clinics will not allow you to use a cab or rideshare if you get sedation.

Ask your healthcare team if sedation will be used. If you do not get sedation, you may not need to arrange a ride home.

What is a bowel prep and why is it needed?

Your lower colon and rectum should be empty and clean for a sigmoidoscopy, so your doctor can see well during the test. You might hear this called a bowel prep.

It can be done with:

• Pills
• Liquids
• Enemas
• A combination of these

Many preps include an enema and/or laxatives to clear out your bowels before the procedure. This often results in frequent trips to the bathroom.  

Talk to your healthcare team about your options for the bowel prep. They will prescribe one for you to follow.

It’s important to read the instructions carefully a few days ahead of time, because you might need to shop for supplies and medicines. If you are not sure about any of the instructions, call your healthcare team and get your questions answered.

During your sigmoidoscopy

A sigmoidoscopy is usually done as an outpatient procedure, meaning you do not need to stay in the hospital overnight.

The test itself usually takes about 10 to 20 minutes. It might take longer if polyps are found and removed or abnormal tissue is biopsied.

Before the test begins

• Your doctor will review the procedure with you and ask you to sign a consent form.
• You will change into a hospital gown and lie on your side on an exam table with your knees pulled up.
• Your blood pressure, heart rate, and breathing will be monitored.
• Most people don’t need to be sedated for this test, but this might be an option for you. If so, you’ll get medicine through a vein (IV) to help you relax.

Your doctor may put a gloved, lubricated finger into your rectum to examine it before the test.

Inserting the sigmoidoscope 

The doctor will gently insert a lubricated sigmoidoscope through your anus and into your rectum, up to the lower part of your colon. The sigmoidoscope is only about 2 feet long (60 cm), so the doctor can only see the rectum and less than half of the colon.

Checking your colon and rectum 

Air is then added into your colon and rectum. This helps the doctor see more clearly. If you are awake, you might feel pressure or an urge to have a bowel movement. As the scope is slowly pulled out, the doctor will carefully check the inside of the lower part of the colon and rectum.

• If any small polyps are found during the test, the doctor may remove them and send them to the lab.
• If any abnormal tissue is seen, the doctor will take a small sample through the scope. It will be tested to see if it’s cancer, a benign growth (not cancer), or something else.       

Is a sigmoidoscopy painful?

You may feel some discomfort during a sigmoidoscopy, but it is not painful.

• If you are not sedated, you might feel pressure and slight cramping in your lower belly during the procedure. To ease discomfort and the urge to have a bowel movement, it may help to breathe deeply and slowly through your mouth. You will feel better as the air leaves your bowels.
• If you are sedated, it will most likely be conscious sedation. This helps you relax and be less aware of what’s happening. You might be awake or fall asleep, and you might feel some pressure or mild cramping.

Whether or not you are sedated, tell your healthcare team if you have pain or if you are uncomfortable so they can help.

After your sigmoidoscopy

You might have bloating, gas pains, or cramps from the air used during the test. If you did not have sedation, you should be able to go back to your normal routine and diet right after the test.

If you had sedation:

• You will be watched closely for problems for about an hour before you can go home.
• You might not remember the procedure.
• Someone will need to drive you home and stay with you until the sedation wears off.

Your doctor or nurse will give you specific instructions to follow after the test. This includes when to restart any medicines you stopped for the procedure.

If biopsies were taken, test results are usually ready within a few days. Some might take longer. You will need to follow up with your healthcare team after the procedure to get your results.

Sigmoidoscopy vs. colonoscopy

What part of the body does the test look at? A sigmoidoscopy looks at the lower portion of your colon (left side). A colonoscopy looks at the whole colon.

How long does it take? A sigmoidoscopy takes less time than a colonoscopy. It also requires less bowel prep. This is because less of your colon is looked at.  

Will I need sedation? You do not need sedation for a sigmoidoscopy. You can usually return to your activities and normal routine right after the test. A colonoscopy uses sedation. You will need someone to drive you to and from the appointment.

Does the test screen for colorectal cancer? Both tests may be used for colorectal cancer screening, but a sigmoidoscopy should be done more often. For people at average risk of colorectal cancer, the American Cancer Society (ACS) recommends: 

• Colonoscopy every 10 years or
• Sigmoidoscopy every 5 years

Possible risks of sigmoidoscopy

Sigmoidoscopy is usually safe, but there are some risks.

Bleeding: If a polyp is removed or a biopsy is done during the sigmoidoscopy, you might notice some blood in your stool for 1 or 2 days after the test. Serious bleeding is uncommon. But in rare cases, bleeding might need to be treated or can even be life-threatening.

Perforation (puncture) of the wall of the colon or rectum: This is rare, but it can be a life-threatening complication. The hole might need to be repaired with surgery.

Drug reactions: If you are sedated during the procedure, the medicines used to help you relax and stay comfortable can sometimes cause changes in blood pressure, confusion, dizziness, or an allergic reaction. You will be watched closely for any medicine side effects. These will be treated, if needed.

When to call your care team

Before you go home, your doctor or nurse should give you specific instructions on when to call about problems.

In general, call your care team if you have:

• Severe abdominal (belly) pain
• Fever
• Swelling or distension in your belly that lasts more than a few days
• Bloody bowel movements
• Dizziness
• Weakness

Be sure you understand what to watch out for, when to call with problems, and the possible timing of when these problems might happen.