Sigmoidoscopy

Sigmoidoscopy usually means flexible sigmoidoscopy. It uses a narrow, bendable tube with a light and camera to examine the inside lining of your rectum and the lower part of your colon, called the sigmoid colon.

The instrument is passed through the anus. It does not examine the entire colon. During the procedure, the clinician can take small tissue samples, called biopsies, or remove some small growths called polyps.

Most people do not need sedation. The procedure is usually completed during an outpatient visit, meaning you go home the same day.

Sigmoidoscopy can help investigate symptoms or monitor a known bowel condition. It may also be offered as a colorectal cancer screening test in some healthcare systems.

Reasons for having it include:

• Bleeding from the rectum or blood in the stool
• An ongoing change in bowel habits, such as diarrhea
• Unexplained lower abdominal or rectal symptoms
• Suspected inflammation, including ulcerative colitis
• Follow-up of a previously found polyp or abnormal test
• Screening for polyps and colorectal cancer

A biopsy can help identify inflammation, abnormal cells, or other changes that may not be clear from appearance alone. Finding an abnormality does not by itself confirm cancer or another specific condition.

Sigmoidoscopy may be suitable when the area of concern is likely to be in the rectum or lower colon. It may also suit someone choosing a screening test that usually requires less preparation and no sedation.

It is not the best test when the entire colon needs to be examined. For example, a colonoscopy may be recommended after a positive stool screening test, unexplained iron-deficiency anemia, or certain findings on sigmoidoscopy.

The procedure may be avoided or delayed if you have:

• A suspected hole in the bowel, called a perforation
• Severe active bowel inflammation or severe acute diverticulitis
• A medical condition that makes the procedure or sedation unsafe at that time
• Bowel preparation that has not cleared enough stool for a useful examination

Pregnancy does not always rule out sigmoidoscopy, but the reason and timing should be considered carefully. Tell the healthcare team if you may be pregnant.

Also tell them if you take blood thinners like warfarin or apixaban, have a bleeding disorder, or have had problems with sedation. These issues do not always prevent the procedure, but they may change the plan.

Your treating facility's own instructions take priority because preparation differs between services and according to whether sedation is planned.

You will usually need an enema, which is liquid placed into the rectum to empty the lower bowel. Some facilities use laxatives or a limited bowel preparation instead. Follow the timing carefully so the clinician can see the bowel lining.

You may be told to change what you eat or drink before the appointment. Fasting is not always needed when no sedation is used, but it may be required if sedation is planned.

Give the facility an up-to-date list of your medicines and supplements. Ask specifically about:

• Blood thinners, including anticoagulants and antiplatelet medicines
• Diabetes medicines or insulin
• Iron tablets

Do not stop a prescribed medicine unless the treating team tells you how and when to do so.

If you will receive sedation, arrange for a responsible adult to take you home. Follow the facility's instructions about whether someone should stay with you afterward.

You will change into a gown and usually lie on your left side with your knees bent. The clinician may first examine the anus and rectum with a gloved finger.

The lubricated sigmoidoscope is then passed gently through the anus and guided into the lower colon. Carbon dioxide or air is introduced to open the bowel so its lining can be seen. This can create pressure, bloating, or the feeling that you need to pass stool.

You may be asked to change position. A nurse may press gently on your abdomen to help the scope move.

If an abnormal area is seen, the clinician may take a biopsy or remove a small polyp using instruments passed through the scope. You should not normally feel a biopsy being taken.

The examination commonly takes about 10 to 20 minutes. It can take longer if treatment is needed or the scope is difficult to advance safely.

Mild cramping, pressure, and bloating are common at first. Passing gas usually helps. A small amount of blood may appear after a biopsy or polyp removal.

You can usually eat and drink normally afterward unless the facility gives you different instructions. Starting with a light meal may feel more comfortable if you have been fasting.

Most people can return to usual activity the same day. Follow any temporary restrictions given after a biopsy or polyp removal.

If you had sedation, do not drive, operate machinery, drink alcohol, or make important decisions for the period specified by your facility. You will need someone else to take you home. If you did not have sedation, you may be able to drive, but confirm this with the facility.

Many people return to work the same day or the next day. Sedation, ongoing cramping, or a physically demanding job may mean taking the rest of the day off.

Sigmoidoscopy is generally well tolerated, but no procedure is risk-free.

Possible complications include:

• Bleeding, particularly after a biopsy or polyp removal
• A tear or hole in the bowel wall, called a perforation
• A reaction to sedative medicines, if they are used
• Infection
• An incomplete examination or an abnormality being missed

A perforation may require hospital treatment and sometimes surgery. Significant bleeding may need another endoscopic procedure or other treatment.

Sigmoidoscopy only examines the lower colon. A normal result does not rule out a problem farther along the colon.

The clinician can usually explain what was seen soon after the procedure. If you received sedation, you may not remember all the discussion, so written information or having another adult present can help.

Biopsy and polyp samples are sent to a laboratory. Results commonly take several days or longer, depending on the facility and the tests required. Ask how and when you will receive them.

Follow-up may include treatment for inflammation, routine screening, or a colonoscopy to inspect the whole colon. A colonoscopy is often considered if a polyp or another important abnormality is found.

Contact the facility if you have not received results within the timeframe they gave you.

The alternatives depend on why sigmoidoscopy has been offered. Each option has different limits.

• Colonoscopy: Examines the entire colon and allows biopsies or polyp removal. It requires more bowel preparation, commonly uses sedation, and usually takes longer.
• Stool screening tests: Easier and do not require a scope, but they can miss polyps or cancers. An abnormal result usually needs a colonoscopy.
• CT colonography: Uses CT scans to examine the whole colon. It still requires bowel preparation, uses radiation, and cannot take a biopsy or remove a polyp.
• Anoscopy or proctoscopy: Examines the anus and rectum with a shorter instrument. It involves less preparation but cannot assess as much of the colon.
• Other imaging: CT or MRI may help assess some bowel problems, but they may not show subtle lining changes and cannot provide a biopsy.

Choosing no immediate procedure may be reasonable in some situations, but it can delay finding the reason for bleeding, inflammation, or another abnormal test. Ask what may be gained or missed with each option.

For routine follow-up, contact the team if mild bleeding continues, symptoms are not settling, or you have questions about eating, medicines, activity, or test results.

Seek urgent medical advice after sigmoidoscopy if you develop:

• Increasing or severe abdominal pain
• Heavy rectal bleeding, clots, or bleeding that does not stop
• Fever or chills
• Persistent vomiting
• Marked dizziness, weakness, or fainting

Call emergency services for severe breathing difficulty, collapse, or rapidly worsening symptoms. Mild gas, brief cramping, and a small spot of blood after a biopsy are usually not emergencies, but contact the team if you are unsure.

Will I be asleep?

Usually not. Most flexible sigmoidoscopies are performed without sedation. Some facilities offer moderate sedation, which makes you relaxed and sleepy but is not the same as general anaesthesia.

Can I drive home?

You must not drive home if you received sedation. Arrange for another adult to take you. Without sedation, driving may be allowed, subject to the facility's instructions.

How painful is a sigmoidoscopy?

You may feel pressure, cramping, bloating, or an urge to pass stool. The procedure should not cause severe pain. Tell the team if you are uncomfortable so they can pause or adjust the scope.

When will I know the results?

You will usually hear what the clinician saw immediately afterward. Biopsy or polyp results take several days or longer because the tissue must be examined in a laboratory.

What if the test finds a polyp?

A small polyp may be removed during the procedure. Because sigmoidoscopy does not inspect the whole colon, you may then be advised to have a colonoscopy.