What’s a Sigmoidoscopy? All About Testing and Diagnosis

What Exactly Is a Sigmoidoscopy?

A flexible sigmoidoscopy is a type of lower GI endoscopy. A healthcare provider uses a thin, flexible tube
with a light and camera (a sigmoidoscope) to examine the lining of your:

• Rectum
• Sigmoid colon (the S-shaped section near the end of the colon)
• Sometimes part of the descending colon (depending on anatomy and how far the scope can comfortably go)

Think of it as a “partial colon check.” It doesn’t examine the entire colon the way a colonoscopy does, but it can still reveal a lotespecially
when symptoms or concerns point to the lower colon.

Flexible vs. Rigid Sigmoidoscopy

You’ll usually hear “sigmoidoscopy” and “flexible sigmoidoscopy” used interchangeably today. There is also a rigid sigmoidoscopy
(using a shorter, rigid scope), which is less common and typically limited to the rectum and very distal colon. For most modern diagnostic work and screening,
the flexible version is the star of the show.

Why Would Someone Need a Sigmoidoscopy?

A flexible sigmoidoscopy can be used for two big buckets: screening and diagnosis.
Sometimes it also serves as a “next step” after another test suggests something might be going on.

1) Screening for Colorectal Cancer (in certain situations)

In the U.S., colorectal cancer screening starts for many average-risk adults at age 45, and there are multiple accepted screening options.
While colonoscopy and stool-based tests are common choices, flexible sigmoidoscopy remains an accepted screening method in some guidelines
and care settingsespecially where it’s accessible and paired with stool testing.

• Flexible sigmoidoscopy may be done every 5 years as a screening option.
• Or it may be done every 10 years when combined with an annual stool test (like FIT), depending on the screening strategy used.

Important nuance: because it doesn’t visualize the entire colon, abnormal findings often lead to a follow-up colonoscopy.
That’s not “failure”that’s the system working as designed.

2) Diagnosing Symptoms

If you’re having lower-GI symptoms, a sigmoidoscopy can help identify the cause. Clinicians may recommend it for:

• Rectal bleeding (especially bright red blood)
• Persistent diarrhea or mucus in stool
• Changes in bowel habits (new constipation, urgency, or “something feels off” patterns)
• Lower abdominal pain or cramping
• Suspected inflammation (like ulcerative colitis affecting the rectum/sigmoid)
• Abnormal findings from imaging or other tests that need a closer look

Real-World Example

Say someone has weeks of rectal bleeding and a lot of urgencyrunning to the bathroom but not passing much. A flexible sigmoidoscopy can help
a provider look for inflammation near the rectum (like proctitis), take biopsies to confirm what’s happening, and decide on the right treatment.

How the Procedure Works (Step-by-Step)

Before the Test: Prep Without the Panic

The goal of prep is simple: clear out the lower colon so the camera can see the lining.
Because the scope doesn’t go through the whole colon, prep is often lighter than a full colonoscopy prepbut it still matters.

Prep varies by clinic, but commonly includes:

• Enemas shortly before the procedure (sometimes one, sometimes two)
• Sometimes a laxative the night before
• Occasionally a clear liquid window (especially if sedation is planned)

You’ll also want to tell your healthcare team about:

• Blood thinners or antiplatelet meds (because biopsies/polyp removal can increase bleeding risk)
• Diabetes meds (fasting/clear liquids may affect dosing)
• Pregnancy, allergies, and major medical conditions
• Any prior reactions to sedation (if sedation is being considered)

Pro tip: plan your schedule like you’re prepping for a long car ride with no rest stopsmeaning, stay close to a bathroom during prep.
Glamorous? No. Effective? Yes.

During the Test: What Actually Happens

You’ll change into a gown and lie on your side. The provider gently inserts the scope through the anus into the rectum and sigmoid colon.
As the scope advances, they may introduce air or CO₂ to open the colon slightly so the lining can be seen clearly.

During the exam, the provider may:

• Inspect the lining for inflammation, ulcers, polyps, or suspicious lesions
• Take biopsies (tiny samples) even if the lining “looks normal” to confirm microscopic inflammation
• Remove small polyps or treat certain bleeding areas (depending on size/location and equipment)

The procedure itself is often fairly quickcommonly around 10 to 20 minutes, though it can take longer if biopsies are taken or a polyp is removed.

Does It Hurt? Do You Get Sedation?

Many people describe the experience as pressure, cramping, or the sensation of needing to pass gas.
It’s usually tolerable without medication, and flexible sigmoidoscopy is often done without sedation.
That said, sedation can be an optionespecially if you’re anxious or if your provider expects a longer exam.

If you receive sedation/anesthesia:

• You’ll likely need someone to drive you home.
• You may be asked not to work, drive, or make major decisions for the rest of the day (because “sleepy you” is not a reliable CEO).

After the Test: Recovery and Immediate After-Effects

Most people can return to normal activities quicklyespecially if no sedation was used. Common short-term effects include:

• Bloating or gas (from the air used during the exam)
• Mild cramps
• Light rectal bleeding if biopsies were taken or a polyp was removed

Your provider may discuss visual findings right away. Biopsy results typically take longer because they must be reviewed by a pathology lab.

What Can a Sigmoidoscopy Diagnose?

Because it directly visualizes the lining of the lower colon, flexible sigmoidoscopy can help identify:

• Inflammatory bowel disease (especially ulcerative colitis that often starts in the rectum)
• Proctitis or colitis (inflammation of the rectum/colon)
• Colon polyps (some types can become cancer over time)
• Colorectal cancer or suspicious masses in the examined area
• Diverticular disease in the lower colon (in some cases)
• Sources of lower GI bleeding (certain lesions, inflammation, or visible bleeding points)

Why Biopsies Matter (Even When Things Look “Fine”)

Some conditions show up under a microscope before they look dramatic on camera. That’s why a provider may take biopsies
even if your colon looks relatively normal. Biopsies can help diagnose certain infections, microscopic inflammation,
or clarify what type of colitis is present.

What It Can’t Do (Limitations You Should Know)

The key limitation is coverage: flexible sigmoidoscopy does not evaluate the entire colon.
If there’s concern for disease higher upor if polyps/cancer are foundyour provider may recommend a full colonoscopy
to evaluate the rest of the colon and remove additional polyps if present.

Risks and Safety: The “What Could Go Wrong?” Section

Flexible sigmoidoscopy is generally considered safe, and serious complications are uncommon. Still, it’s a medical procedureso it’s fair
to want the honest rundown.

Possible Complications

• Bleeding, especially after a biopsy or polyp removal
• Perforation (a tear in the colon wall), which is rare but serious
• Reactions related to sedation if sedation is used
• Temporary discomfort: cramps, bloating, and gas

When to Call Your Doctor Afterward

Mild cramping and a little blood after biopsy can be normal. But contact your healthcare team urgently if you have:

• Severe or worsening abdominal pain
• Fever or chills
• Heavy rectal bleeding (or bleeding that doesn’t improve)
• Dizziness, fainting, or shortness of breath

Translation: if your body is sending you “this is not a normal day” signals, don’t tough it outcall.

Understanding Results: What Happens Next?

Normal Result

A “normal” sigmoidoscopy means the examined lining looks healthy and no suspicious polyps, inflammation, or masses were seen
in the rectum and lower colon. Depending on why the test was done, your provider may still consider other explanations for symptoms
(diet, medications, functional bowel disorders, infections, or issues located beyond what the scope can see).

Abnormal Result

If something is found, the next steps depend on what it is:

• Polyps: small polyps may be removed; pathology determines type and follow-up.
• Inflammation: biopsies help confirm IBD or other causes; treatment may start based on findings.
• Suspicious lesions/mass: biopsy and often a full colonoscopy and imaging for staging/workup.

If polyps or cancer are found, providers often recommend a colonoscopy because abnormalities in the lower colon can sometimes
be a clue that more may be present elsewhere.

Sigmoidoscopy vs. Colonoscopy vs. Stool Tests

Here’s a practical comparisonbecause you deserve to know why your clinician chose this test and not another.

Flexible Sigmoidoscopy

• Pros: often quicker prep; usually no sedation; can diagnose and biopsy lower-colon issues; can remove some polyps.
• Cons: doesn’t examine the full colon; abnormal findings may require colonoscopy.

Colonoscopy

• Pros: examines entire colon; removes most polyps during the same procedure; strong “one-stop shop” for screening + intervention.
• Cons: more extensive bowel prep; usually involves sedation; more recovery time the day of.

Stool-Based Tests (like FIT or stool DNA tests)

• Pros: noninvasive; at-home option; no scope.
• Cons: if positive, you’ll need a colonoscopy; does not directly visualize or treat polyps.

Bottom line: the “best” test is the one that fits your health situation, risk factors, and accessand that you’ll actually complete.
If you’re doing diagnostic evaluation for symptoms, direct visualization (sigmoidoscopy or colonoscopy) is often more informative than stool tests.

Frequently Asked Questions

How long does it take?

The scope time is often around 10–20 minutes, but plan extra time for check-in, prep, and post-procedure discussion.

Can I go back to work afterward?

If you didn’t receive sedation, many people resume normal activities the same day. If sedation was used, expect a “take it easy” day.

Will I be embarrassed?

Almost everyone feels a little awkward at first. Then the staff walks in with the calm confidence of people who do this all day,
and your embarrassment usually drops by about 80%. They’re focused on medical care, not judging your colon’s personality.

What if they find something?

That’s the point of the testfinding answers. Many findings are treatable. Polyps can often be removed, inflammation can be managed,
and concerning lesions can be investigated early (which is exactly when you want them found).

Patient Experiences: What It’s Really Like (500+ Words of Real-World Perspective)

Let’s talk about the part people often Google at 2:00 a.m.: “What does a sigmoidoscopy actually feel like?”
Everyone’s experience is a little different, but there are common themes patients reportespecially around prep, comfort, and the “surprisingly not terrible”
realization afterward.

The Prep: The Least Fun Part (But Usually the Shortest)

Many people say the prep is the most annoying piecenot because it’s painful, but because it’s inconvenient.
Enemas work quickly, and that’s both a blessing and a logistical warning. Patients often describe:

• Needing to stay near a bathroom for a while
• Feeling “empty” (mission accomplished) but a bit tired of the bathroom commute
• Wishing they had stocked up on soft toilet paper ahead of time (wisdom comes from experience)

If your prep includes clear liquids, people commonly recommend choosing options you don’t hatebroth, tea, electrolyte drinksbecause it’s easier to stick with.
And yes, people do get oddly passionate about which clear liquids are “the least depressing.”

During the Procedure: Pressure, Cramping, and a Lot of Deep Breaths

In the procedure room, the most commonly reported sensations are pressure and cramping.
The cramping is often linked to the air/CO₂ used to open the colon for better viewing. Patients frequently say:

• “It was uncomfortable, but manageable.”
• “The cramps came in waves.”
• “Breathing slowly helped a lot.”

People who go without sedation often appreciate being able to leave quickly and return to normal activities sooner.
People who choose sedation often say it helped with anxiety and made the procedure feel like a blur.
Neither choice is “tougher” or “better”it’s about what helps you complete the test safely and calmly.

The Awkward Factor: Bigger in Your Head Than in the Room

Many patients worry they’ll feel embarrassed. In reality, the clinical team tends to be efficient, professional, and (thankfully) unbothered.
A common sentiment is that the awkwardness peaks in the waiting room and drops once the process startsbecause the staff has clearly done this a thousand times.
Patients often feel reassured when clinicians explain what they’re doing as they go and check in about comfort.

Afterward: Gas Happens (And It’s Not a Personality Flaw)

The most common post-procedure “experience” is gas. People report bloating and passing gas as the air used during the exam works its way out.
It can feel funny, a little uncomfortable, andlet’s be honestslightly comedic. Many patients say walking a bit afterward helps relieve bloating.
If biopsies were taken, light bleeding can happen, and patients commonly describe it as minimal and short-lived.

Tips Patients Commonly Wish They’d Known

• Ask questions early: sedation options, prep steps, and medication instructions are easier to handle when clarified ahead of time.
• Plan the day: even without sedation, give yourself buffer time; with sedation, plan for rest.
• Communicate discomfort: clinicians can pause, adjust, and guide breathing/positioning to help.
• Remember the “why”: people often feel relieved afterwardbecause uncertainty is stressful, and answers help.

The biggest “experience takeaway” is this: most patients report that the anticipation is worse than the procedure. It’s normal to be nervous, but flexible sigmoidoscopy
is a widely used tool for good reasonbecause it can provide valuable information quickly, and sometimes even treat the issue right away.