Flexible Sigmoidoscopy

The information on this page mainly applies to patients having their procedure on an out-patient basis. The arrangements are slightly different when the examination is given to patients whom have already been admitted as an in-patient.

What is a flexible sigmoidoscopy?

A flexible sigmoidoscopy (often referred to as a flex sig) is a test that lets the doctor see the lining of your rectum and a short section of your large intestine (colon).

How do I prepare for a flex sig?

Your colon must be completely clean for a good test. The doctor will tell you how to clean your colon.

Flexible sigmoidoscopy preparation usually includes the following guidelines:

  • Tell your doctor if you have any allergies.
  • Bring with you all prescription and over-the-counter medicines you are taking.
  • Bring with you all medical records and X-ray films that are related to your current problem.
  • A color illustration depicting a flexible sigmoidoscopy procedure.
  • Sigmoidoscope inserted into the sigmoid colon through the anus and rectum.


Sigmoidoscope inserted into the sigmoid colon through the anus and rectum. 
Sigmoidoscope inserted into the sigmoid colon through the anus and rectum.


What will happen during a flexible sigmoidoscopy?

When you come for the flexible sigmoidoscopy, the nurse and doctor will talk to you about the test and answer any questions. You should know why you are having the flexible sigmoidoscopy and the possible risks. You will be asked to sign a consent form which gives the doctor your permission to do the test.

You will put on a hospital gown. The nurse will put a needle (IV) into a vein, usually in your arm or back of your hand. You may receive antibiotics through the IV at this time.

You will lie down on a padded table with a sheet for covering. You will be taken to the exam room.

A blood pressure cuff will be put on your arm or leg and a small sensor will be put on your finger. These will let the nurse check your blood pressure and heart rate during the test.

You will be asked to lie on your left side. The doctor will do a rectal exam to check for any problems.

Next, the doctor will insert a thin, flexible tube (endoscope) into your rectum and gently move the endoscope into the colon. As the doctor moves the endoscope, air will be added to your colon. The air opens your colon and makes it easier for the doctor to pass the endoscope safely. You may experience a feeling of pressure or cramping as the air is added.

When the endoscope is in the left side of the colon, the doctor will withdraw the endoscope slowly, looking at the lining of the colon for any problems. The entire test should last about ten minutes.

The great majority of these tests are done with no sedation given the brief nature of the procedure and the fact that it is well tolerated by most. However, the doctor may decide to use sedation in special cases.

What treatments can be done during a flexible sigmoidoscopy?

  • Biopsy: If your doctor thinks an area of the lining needs to be looked at more closely he will take a small piece (biopsy). This piece is sent to the lab to be examined.
  • Cauterization: If the doctor finds an area of bleeding, it can be controlled by applying medicines through the endoscope directly onto the area of bleeding. The doctor can also insert a small, heated wire through the endoscope and seal off the blood vessels with a heat treatment (cauterization). You will not feel this treatment.
  • Polyp Removal: If the doctor finds polyps on the lining of the colon, they may be removed. Polyps vary in size from a tiny dot to several inches. Most polyps are non-cancerous but the doctor cannot tell a non-cancerous polyp by its looks. For this reason, if the doctor removes a polyp, it is sent to the lab for further tests. Removal of polyps is an important way of preventing colon cancer.

What will happen after a flexible sigmoidoscopy?

  • If you did not get sedation during the test you will be able to leave. The nurse will give you written instructions to follow when you go home. The doctor will talk to you about the test before you leave. If you have any questions, please ask.
  • If you did receive sedation, you will be taken to the recovery room.
  • A nurse will check your blood pressure and heart rate as you rest. You will wake-up in about 30 minutes.
  • The nurse will give you written discharge instructions to follow when you go home. If you have any questions, please ask.
  • Your IV will be removed. The doctor will talk to you about the flexible sigmoidoscopy before you leave.
  • You may have some cramping or bloating because of the air placed in your large intestine during the flexible sigmoidoscopy. This should go away with the passage of gas (flatus). You should be able to eat after the test, but your doctor may restrict your diet and activities for the rest of the day.
  • If a problem occurs during flexible sigmoidoscopy, you may need to stay overnight in the hospital.

Over the next 24 hours....

  • If you received sedation, do not drive, operate machinery, sign legal documents or make important decisions.
  • If you received sedation, you must have someone with you to take you home.
  • Do not drink alcohol or take sleeping and/or nerve pills.

Call your doctor if you have severe pain, vomiting, rectal bleeding or fever above 101°F during the next few days.

What are the risks of having a flex sig?

As with any procedure, there are risks to a flexible sigmoidoscopy.

  • A tender lump may form where the IV was placed. The lump may not go away for several weeks. You will need to call your doctor if redness, pain or swelling in that area lasts more than two days.
  • You may develop a rash or hives, a dry mouth or redness of the face (flushing).
  • The medicines may make you sick. You may have nausea and vomiting.
  • Bleeding and tearing (perforation) of the large intestine lining is very rare. Bleeding is usually minor and easily controlled. In rare cases, blood transfusions or emergency surgery may be needed.