What is sigmoidoscopy? What to expect when undergoing this test

By Cristiano Antonino Last updated Mar 26, 2022

A sigmoidoscopy is a way for a healthcare provider to examine the last one-third of the large intestine. This includes the rectum and sigmoid colon

During the test, a flexible viewing tube with a lens and light source on the end, called a sigmoidoscope, is inserted through the anus and into the rectum.

Then, looking through the eyepiece at the other end of the scope, the practitioner can see the inside of the colon.

The test’s purpose is to check for cancer, abnormal growths (polyps), and ulcers.

Most of the time, a sigmoidoscopy is done by a gastroenterologist or a colorectal surgeon.

The test can be uncomfortable because there is no sedation, but most practitioners keep the test very quick to cut down on patient discomfort.

If there is prep and sedation, the test might take longer.

Purpose of sigmoidoscopy

Flexible sigmoidoscopy is a screening test.

It is used to identify abnormalities in the lower colon and rectum.

However it is not widely used as a screening tool for colorectal cancer.

Your healthcare provider may recommend the procedure if you are experiencing:

Abdominal pain
Rectal bleeding
Chronic diarrhea
Unusual bowel habits
Other intestinal troubles

Most healthcare providers recommend colonoscopy for colorectal cancer screening.

That’s because, unlike sigmoidoscopy, colonoscopy can view the entire colon.

In addition, practitioners can remove polyps during a colonoscopy.

Even so, sigmoidoscopy has some advantages, including:

It’s a faster procedure
Requires less prep time
It does not require anesthesia

A sigmoidoscopy may also be used as a follow-up procedure if a digital rectal exam is abnormal or after a positive fecal occult blood test.

It can also help identify the source of rectal bleeding or other problems in the lower digestive tract.

If your healthcare provider finds something unusual during the procedure, they may be able to do a biopsy.

For example, if an abnormality is found in a sigmoidoscopy, your healthcare provider will probably want to follow up with a colonoscopy.

Sigmoidoscopy, screening recommendations

Medics recommends colorectal cancer screening for adults between the ages of 45 and 75.

Adults over 75 may be selectively screened.

Flexible sigmoidoscopy is one of the recommended screening options.

If this option is chosen, it should be repeated every five years.

Colonoscopy is another recommended screening option and only needs to be repeated every 10 years.

Some people at a higher risk for colorectal cancer may need to begin screening earlier.

High-risk groups include those with:

Inflammatory bowel disease (such as Chron’s disease or ulcerative colitis)
A family history of colorectal cancer or polyps
A genetic syndrome like familial adenomatous polyposis (FAP) or hereditary Lynch syndrome

Risks of sigmoidoscopy

Like all medical procedures, sigmoidoscopy comes with certain risks.

These include:

Bleeding
Perforation to the colon (a puncture in the organ)
Abdominal pain
Death (rare)

Bleeding and damage to the colon are the most common complications of sigmoidoscopy. Bleeding may occur up to two weeks following the procedure.

Symptoms of an Emergency

Seek medical care right away if you notice any of the following after your procedure:

Severe abdominal pain
Fever
Bloody bowel movements
Bleeding from anus
Weakness or dizziness

Sigmoidoscopy, Before the Test

For the healthcare provider to get a clear view of the intestinal wall, the colon must be empty.

The practitioner will give you specific instructions on how to prepare for the test. Preparation usually includes:

Bowel prep that uses laxatives or enemas
Diet consisting mainly of liquids (for example, broth, gelatin, plain coffee or tea, light-colored sports drinks and fruit juices, and water)

Be sure to talk to your healthcare provider about any medications you are taking so that they can advise you on whether to continue taking your medications or if you need to abstain from taking any of them for the procedure.

During the sigmoidoscopy

A sigmoidoscopy is usually performed at a hospital or outpatient surgical center.

The procedure usually takes about 20 minutes.

On the day of the test:

Gown: You may be asked to wear a hospital gown or remove your clothes from the waist down.
Vitals: A nurse or medical assistant may record temperature, pulse, blood pressure, and respiratory rate.
Position: Your healthcare provider will instruct you to lie on your left side on the exam table, with one or both knees raised to your chest.
Scope insertion: Your healthcare provider will insert the sigmoidoscope into your rectum. They may pump air through the scope if necessary for a clearer view.
Image: The camera on the scope will send an image for your practitioner to view.
Biopsy: During the procedure, your healthcare provider may perform a biopsy if they see something suspicious. They will do this using a device at the end of the sigmoidoscope. The tissue they collect can then be sent to a lab for further analysis under a microscope.