When a doctor recommends a sigmoidoscopy, it often comes with a mix of curiosity and mild anxiety. What exactly is it? Why do I need one? Will it hurt? These are the questions most people have when they first hear about the procedure. The short answer: a sigmoidoscopy is a safe, quick, and highly effective way to examine the lower part of your large intestine—the sigmoid colon and rectum—to check for problems like bleeding, polyps, inflammation, or early signs of cancer.
At Prime Hospital Panipat, our gastroenterology team performs sigmoidoscopies regularly, and we always take time to explain everything clearly so patients feel informed and at ease. This procedure is one of the most common tools used to investigate digestive symptoms and screen for colorectal issues. In this detailed guide, we’ll cover everything you need to know about what is a sigmoidoscopy, why it’s done, how it’s performed, what to expect, preparation tips, risks, benefits, recovery, and how it compares to other tests like colonoscopy.
What Is a Sigmoidoscopy? Understanding the Basics
A sigmoidoscopy is a minimally invasive diagnostic procedure that uses a thin, flexible tube called a sigmoidoscope to look inside the rectum and the lower (sigmoid) portion of the colon. The sigmoidoscope is about the thickness of a finger and is equipped with a tiny camera and light at the end, allowing the doctor to see the lining of the bowel on a monitor.
The procedure examines only the distal (lower) third of the large intestine—specifically the rectum and sigmoid colon—unlike a full colonoscopy, which views the entire colon. Because it only looks at the lower part, a sigmoidoscopy is quicker (usually 10–20 minutes) and often requires less preparation than a colonoscopy.
There are two main types:
- Flexible sigmoidoscopy — The most common type, using a flexible tube for better comfort and reach.
- Rigid sigmoidoscopy — An older method using a stiff tube; rarely used today except in specific situations.
The flexible version is preferred because it causes less discomfort and allows the doctor to navigate curves in the colon more easily.
Why Is a Sigmoidoscopy Performed? Common Reasons and Indications
Doctors recommend a sigmoidoscopy for several important reasons:
1. Investigating Symptoms Persistent rectal bleeding, changes in bowel habits (diarrhea, constipation), abdominal pain, mucus or pus in stool, unexplained weight loss, or anemia can all prompt a sigmoidoscopy to find the cause.
2. Screening for Colorectal Cancer While not as comprehensive as colonoscopy, sigmoidoscopy can detect polyps and early cancers in the lower colon. Some guidelines recommend it every 5 years for average-risk individuals, often combined with stool tests.
3. Monitoring Inflammatory Bowel Disease For patients with ulcerative colitis or Crohn’s disease affecting the lower colon, regular sigmoidoscopy helps track inflammation, check for healing, or detect complications like strictures.
4. Evaluating Polyps and Abnormal Growths If a stool test (like FIT or FOBT) shows blood, a sigmoidoscopy can locate and sometimes remove polyps.
5. Post-Treatment Follow-Up After polyp removal or treatment for inflammation, doctors may use sigmoidoscopy to ensure everything is healing properly.
6. Diagnosing Infections or Other Conditions It can identify infections, diverticulosis, hemorrhoids, or anal fissures.
In short, sigmoidoscopy is a targeted tool for the lower bowel—perfect when symptoms point to that area or when full colonoscopy isn’t needed.
How Is a Sigmoidoscopy Performed? Step-by-Step Process
Understanding the procedure step by step can ease a lot of anxiety.
Before the Procedure You’ll receive clear instructions on preparation (more on that below). You may be asked to arrive at the hospital or clinic wearing loose clothing. Most sigmoidoscopies are done without sedation, though mild sedation is available if you’re anxious.
During the Procedure
- You lie on your left side with knees bent.
- The doctor gently inserts the lubricated sigmoidoscope into the rectum.
- Air is gently pumped in to open the bowel for better viewing (this may cause temporary cramping or pressure).
- The scope is advanced slowly through the rectum and into the sigmoid colon.
- The doctor examines the lining on a monitor, looking for abnormalities.
- If needed, small biopsies (tissue samples) can be taken painlessly, or tiny polyps can be removed using a snare.
- The scope is slowly withdrawn while the doctor continues inspecting.
The entire process usually takes 10–20 minutes. You’ll feel some pressure or cramping from the air, but most patients describe it as uncomfortable rather than painful.
After the Procedure You’ll rest briefly in the recovery area. You can usually eat and drink right away and resume normal activities the same day. If biopsies were taken, results come back in a few days.
Preparation for Sigmoidoscopy: What You Need to Do
Preparation is simpler than for a full colonoscopy because only the lower colon needs to be clear.
Common Prep Instructions
- Diet: Clear liquids only (broth, tea, clear juices, water) the day before.
- Laxative: A single enema or mild laxative (like sodium phosphate or magnesium citrate) the evening before and/or morning of the procedure.
- No food: Nothing by mouth for a few hours before.
- Medications: Tell your doctor about all medicines, especially blood thinners.
The goal is a clean lower colon for clear viewing. Unlike colonoscopy, you don’t need a full bowel prep with large volumes of laxative solution.
What to Expect During and After a Sigmoidoscopy
During
- Mild discomfort or cramping from air insufflation.
- Feeling of pressure as the scope moves.
- No significant pain for most patients (sedation is optional).
After
- You may feel bloated or pass gas for a few hours (normal after air introduction).
- Mild spotting if biopsies or polyp removal occurred.
- Resume normal diet and activities immediately.
- Rare complications (bleeding, perforation) are extremely uncommon.
Most people feel fine within minutes and go home the same day.
Risks and Complications of Sigmoidoscopy
Sigmoidoscopy is very safe, with a low complication rate.
Possible risks (rare):
- Bleeding (usually minor and self-limiting).
- Perforation (tear in the colon wall) — less than 1 in 10,000.
- Infection (extremely rare).
- Reaction to sedation (if used).
The risk of serious complications is much lower than with colonoscopy because the scope doesn’t travel as far.
Benefits of Sigmoidoscopy: Why It’s a Valuable Tool
- Quick and minimally invasive.
- Requires less prep than colonoscopy.
- Can detect and remove polyps in the lower colon.
- Excellent for investigating lower bowel symptoms.
- Lower cost and faster recovery.
- Can be done in an outpatient setting.
When combined with stool tests, it provides good screening coverage for the lower colon.
Sigmoidoscopy vs. Colonoscopy: Key Differences
Many people confuse the two—here’s a clear comparison:
Sigmoidoscopy
- Examines rectum and sigmoid colon only.
- Shorter (10–20 min).
- Less prep (enemas).
- Usually no sedation.
- Lower risk.
- Good for lower colon issues.
Colonoscopy
- Examines entire colon.
- Longer (30–60 min).
- Full bowel prep.
- Often sedated.
- Higher risk (still low).
- Gold standard for full screening.
Doctors choose sigmoidoscopy when symptoms point to the lower bowel or when full colonoscopy isn’t needed.
Who Should Get a Sigmoidoscopy? Screening and Diagnostic Guidelines
Screening Guidelines vary, but some recommend sigmoidoscopy every 5 years starting at age 50–75 for average-risk individuals (often with FIT testing).
Diagnostic Anyone with:
- Rectal bleeding.
- Persistent changes in bowel habits.
- Unexplained anemia.
- Inflammatory bowel disease symptoms.
- Family history of colorectal cancer/polyps.
Recovery and Follow-Up After Sigmoidoscopy
Recovery is straightforward:
- Rest for a short while.
- Eat normally.
- Resume activities the same day.
- Watch for excessive bleeding, severe pain, or fever (call your doctor if these occur).
Follow-up depends on findings—biopsy results guide next steps.
Conclusion: Sigmoidoscopy – A Safe, Effective Way to Check Your Lower Bowel
What is a sigmoidoscopy? It’s a quick, low-risk procedure that gives your doctor a clear view of the rectum and sigmoid colon to investigate symptoms or screen for problems. It’s an important tool in digestive health—helping catch issues early and guiding treatment.
If you’re experiencing rectal bleeding, bowel changes, or have been advised to have one, know that it’s a routine, well-tolerated exam. At Prime Hospital Panipat, our experienced gastroenterologists perform sigmoidoscopies with care and clear communication, ensuring you feel comfortable and informed every step of the way.
Don’t hesitate to ask questions or seek care if something feels off. Early detection makes all the difference in digestive health.