Flexible Sigmoidoscopy Test and Procedure
Overview
Flexible sigmoidoscopy is a medical test that allows doctors to examine the lower part of the large intestine. They use a slender, bendable tube called a sigmoidoscope, which has a small light and camera at the end.
This tool helps the doctor view the inside of the anal canal, rectum, sigmoid colon, and descending colon. The tube does not reach the entire colon—it stops before the transverse colon.
Key Areas Examined:
- Anal canal
- Rectum
- Sigmoid colon
- Descending colon
Flexible sigmoidoscopy helps doctors detect abnormal changes in the colon wall, such as polyps or unusual tissue that could develop into cancer. During the procedure, special tools may be used to remove polyps or take small tissue samples (biopsies) for further testing.
If the exam reveals polyps or signs of cancer, the doctor may recommend a full colonoscopy. Colonoscopy examines the entire colon, allowing a more complete look for any additional problems farther along the large intestine.
| Term | Area Examined |
|---|---|
| Flexible Sigmoidoscopy | Rectum, sigmoid, descending colon |
| Colonoscopy | Whole colon, including transverse colon |
Reasons for the Test
Checking for Cancer and Abnormal Growths
Doctors often choose flexible sigmoidoscopy to help detect colon cancer and polyps in the lower part of the large intestine. Many health experts recommend starting this screening around age 45 for people at average risk. Those with higher risk, such as a family history of colorectal cancer, may need to begin screening by age 40.
This screening is often repeated every five years until age 75. People who also do annual stool tests (like the fecal immunochemical test) may be able to go longer between sigmoidoscopies. After age 75, the need for continued screening depends on a person’s overall health and previous test results.
Flexible sigmoidoscopy generally requires less preparation than a colonoscopy. Most patients do not need sedation, and the risk of injury to the colon or rectum is lower.
Common Conditions Checked
- Polyps (which can lead to cancer)
- Colorectal cancer
- Rectal cancer
Additional Reasons for the Exam
Doctors use flexible sigmoidoscopy to investigate symptoms such as ongoing stomach pain, bleeding from the rectum, steady changes in stool, or unexpected weight loss.
Other Conditions Assessed
| Condition | Description |
|---|---|
| Diverticulosis | Small bulges in the colon wall |
| Colitis and Proctitis | Swelling in the colon or rectum |
| Ulcerative Colitis and Crohn’s | Forms of inflammatory bowel disease |
| Pseudomembranous colitis, IBD, IBS | Swelling, infection, or bowel syndrome |
| Constipation, fecal incontinence | Trouble with bowel habits |
| Solitary rectal ulcer syndrome | Rare sore in the rectum |
| C. difficile infection | Infection causing diarrhea and cramps |
This exam provides doctors with important information to diagnose digestive diseases and monitor people with ongoing bowel problems.
Possible Complications
Flexible sigmoidoscopy is considered safe, but some risks are possible. Rare problems include:
- Rectal bleeding, especially after a biopsy
- Perforation (a tear in the colon or rectum wall)
- Mild cramping or bloating
- Abdominal pain
Severe complications like blood transfusions, surgery, or inflammation are very uncommon. Most side effects are minor and temporary.
How You Get Ready
Proper preparation helps the doctor see the colon clearly during a flexible sigmoidoscopy. Most people follow a clear liquid diet the day before the procedure. This includes drinking fat-free broth, water, clear juices (like apple or white grape), certain sports drinks, clear gelatins, and tea or coffee without milk or cream. Solid foods and dark-colored drinks are usually not allowed.
Doctors often prescribe a bowel prep kit to clear out the colon. This kit may include laxatives (in pill or liquid form) and sometimes an enema. Laxatives help move stool out of the body, while enemas use liquid inserted into the rectum to empty the lower part of the colon. Patients should follow the prep instructions carefully and stay near a restroom, as frequent bowel movements are common.
Patients may also need to adjust their medications. Many people take daily medicines, vitamins, or supplements. It’s important to tell the healthcare provider about all regular medications—especially iron supplements, diabetes drugs, aspirin, or blood thinners. The doctor may advise stopping certain medicines or changing how they are taken before the test.
Some people receive sedation or anesthesia during the procedure. If that’s the case, someone should be ready to drive the patient home afterward. Even if sedation isn’t used, having someone available to assist is a good idea for safety.
| Preparation Step | What to Do | Notes |
|---|---|---|
| Diet | Drink only clear liquids. | No solid food before the procedure. |
| Bowel Prep | Use a prep kit, take enemas. | Follow exact instructions. |
| Medications | Tell your doctor about all medications. | Some may need stopping or a dose change. |
| After the test | Arrange a ride home. | Needed if sedation is used. |
What You Can Expect
While the Procedure Is Happening
Most people do not need anesthesia or strong pain medicine during a flexible sigmoidoscopy. Sometimes, a medicine is given to help relax the patient or cause mild drowsiness. Healthcare staff will provide a hospital gown and ask the patient to lie on their left side, drawing the knees up to allow better access to the rectum.
The healthcare provider gently inserts the sigmoidoscope into the anus and guides it through the rectum and into the lower part of the colon. Air mixed with carbon dioxide is used to expand the colon, making it easier to see the inside. Some people may feel cramping or an urge to use the bathroom during the exam.
The sigmoidoscope’s camera sends clear images of the colon lining to a screen. If needed, the provider may use special tools through the scope to take tissue samples for testing. The procedure usually takes 15 to 20 minutes, though it may last a bit longer if more samples are needed.
After the Procedure Is Finished
After the test, it’s normal to feel mild stomach discomfort or bloating. Walking can help relieve gas within a few hours. Most people can eat normally and return to their usual activities right away—unless they received a relaxing medicine, in which case they should avoid driving for a while.
If tissue was removed or samples were taken, it’s normal to see a small amount of blood with the first bowel movement. However, it’s important to report any of the following to your healthcare provider:
- Heavy bleeding or clots in stool
- Ongoing bleeding from the rectum
- Strong or lasting belly pain
- Fever higher than 100°F (37.8°C)
Quick Reference Table
| Step | What to Expect |
|---|---|
| During exam | Insertion of sigmoidoscope, possible cramping, images taken |
| After exam | Mild discomfort, possible mild bleeding, quick recovery |
Findings
Doctors can often provide sigmoidoscopy results shortly after the procedure, but some findings may take a few days if lab work is required. If no abnormal tissue is found, the result is considered negative. If the doctor finds polyps, signs of cancer, or other abnormal tissue, the result is considered positive.
When polyps or biopsies are collected, a specialist examines them in a laboratory. These additional tests help confirm a diagnosis and guide the next steps in treatment. If positive findings are present, doctors often recommend a colonoscopy to check the entire colon.
| Result Type | What It Means |
|---|---|
| Negative | No abnormal tissue found |
| Positive | Polyps, cancer, or abnormal tissue found |
| Biopsies/Polyps | Sent to lab for review |
If images are unclear during the procedure, the doctor may suggest additional screening or diagnostic tests.
