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CION Cancer Clinics
Sigmoidoscopy as a screening test: what it checks and what it misses | CION Cancer Clinics
A flexible sigmoidoscopy is a short camera test of the rectum and lower colon, usually done without sedation. It can find and remove polyps in the part it reaches, but it sees less than half of the colon. If it finds an adenoma, a full colonoscopy usually follows. This page explains who it suits, what happens on the day and where it falls short. At CION Cancer Clinics, our specialists help you judge which bowel symptoms need tests and plan screening that fits your risk.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
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On this page
- What is a flexible sigmoidoscopy, and what does it check?
- Is sigmoidoscopy a sensible screening choice for you?
- What actually happens during a sigmoidoscopy?
- The words you may see on a sigmoidoscopy report
- Three things people assume about sigmoidoscopy
- What this page cannot tell you
- Common questions about sigmoidoscopy screening
The short answer
What is a flexible sigmoidoscopy, and what does it check?
A flexible sigmoidoscopy is a short camera test of the lower bowel. A thin, bendy tube with a light is passed through the back passage to look at the rectum and the lower part of the colon. It sees less than half of the colon's length, which is the main thing to understand about it.
Why it works as a screening test
Most colon cancers grow slowly from small growths called polyps. A polyp is a small lump on the inner lining of the bowel, and most are harmless. The scope can find polyps in the part it reaches and remove small ones on the spot. Taking a polyp out before it changes is how this test lowers the chance of cancer in that part of the bowel.
What it cannot see
The upper colon, on the right side of the belly, is out of reach. A clear sigmoidoscopy says nothing about that part. Cancers on the right side of the colon often cause no early symptoms, so that blind spot matters. If the scope finds an adenoma, a type of polyp that can turn into cancer over time, you will usually be offered a full colonoscopy to check the rest.
A screening test sorts people into those who need a closer look and those who probably do not. It is not a diagnosis.Who it is for
Is sigmoidoscopy a sensible screening choice for you?
Guideline bodies list it as one accepted option for people at average risk. It suits some people well and others not at all.
Average risk, no symptoms
You are in your mid-forties or older, feel well, and have no strong family history. A sigmoidoscopy every few years, or combined with a yearly FIT stool test, is one reasonable way to screen.
Usually a better fit if you
- Want a scope but would rather avoid sedation
- Need to travel home alone the same day
- Accept that a polyp may still mean a full colonoscopy
Who it does not suit
Anyone with bleeding, a change in bowel habit, weight loss or anaemia, a low haemoglobin, is not in the screening group. Bleeding that the family has put down to piles counts. You need a full colonoscopy, chosen by a doctor who has examined you.
Higher risk needs the whole colon
A parent or sibling with colon cancer, Lynch syndrome, polyposis or long-standing colitis all call for full colonoscopy. A test that sees only half the bowel is not enough here. The family history pathway explains the timing.
Not sure whether this applies to you?
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What actually happens during a sigmoidoscopy?
A lighter preparation
You do not drink large amounts of laxative. Most people use one or two enemas, a small amount of liquid squeezed into the back passage, at home or at the centre shortly before the test. It clears only the lower bowel, which is all the scope needs.
Usually no sedation
You lie on your left side with your knees bent. Most people stay awake, so you can eat normally afterwards and travel home on your own. Tell the team beforehand about blood thinners, diabetes medicines or a heart condition.
The scope and the air
The tube is passed gently and a little air opens up the bowel. You may feel cramping or pressure, like trapped wind, which eases as the air passes. The look itself usually takes only a few minutes.
Polyps and the result
Small polyps can be removed or sampled during the test and sent to a laboratory. The doctor can often tell you what was seen before you leave. Laboratory results follow later, and if they show an adenoma, CION arranges the colonoscopy that comes next.
On your report
The words you may see on a sigmoidoscopy report
- Extent of examination
- How far the scope went. If it stopped early, part of the lower colon was not seen and the test may need repeating.
- Hyperplastic polyp
- A common small polyp, usually in the lower bowel, that rarely turns into cancer.
- Adenoma
- A polyp that can slowly turn into cancer if left. Finding one usually leads to a full colonoscopy.
- Polypectomy
- Removal of a polyp through the scope, usually with a small wire loop. It does not involve any cut on the skin.
- Diverticula
- Small pouches in the bowel wall, very common with age. They are not cancer and are usually just noted.
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Commonly believed
Three things people assume about sigmoidoscopy
"It is a short colonoscopy, so it checks the same thing."
It checks the same lining, but only the lower part. A clear sigmoidoscopy cannot speak for the upper colon. That is why guidelines repeat it more often than a clear colonoscopy, or pair it with a yearly stool test.
"A clear result means I can ignore any symptoms for years."
A clear screen only describes the day it was done and the part of the bowel it reached. New bleeding, a change in habit or weight loss after a clear test still needs a doctor. Do not let an old report delay a visit.
"If they found a polyp, it must be cancer."
Most polyps are not cancer, and many never would be. Finding and removing one is the test doing its job. The laboratory report says what type it was, and that decides whether you need a full colonoscopy and when to check again.
Being straight with you
What this page cannot tell you
It cannot tell you which screening test is right for you. That depends on your age, your family history, your medicines, your other health problems and what you are willing to go through. The choices are laid out side by side on the screening options page, and a doctor can help you weigh them in one conversation.
It cannot read your report
The same polyp can mean different things depending on its type, size and number. The laboratory report, not the look of the polyp on the day, decides what happens next. Bring both reports to the doctor who ordered the test, or to a CION consultation, rather than searching each word.
Who this does not apply to
If you have symptoms, a strong family history or a known gene fault, this page is not for you. Screening advice is written for people who are well. Sigmoidoscopy also looks at the rectum, and rectal cancer is treated differently from colon cancer. If a growth is found low down, the rectal cancer section is the one to read.
Not sure which group you are in? Call the CION helpline and describe your situation. Someone will tell you honestly which test is worth arranging.Questions we are asked
Common questions about sigmoidoscopy screening
Does a sigmoidoscopy hurt?
Most people feel pressure and cramping while air is in the bowel, which eases quickly afterwards. It is usually done without sedation and is often better tolerated than people expect. Tell the doctor if it becomes uncomfortable, because they can slow down or let some air out.
Is sigmoidoscopy as good as a colonoscopy?
Not for the whole bowel. It looks at less than half of the colon, while a colonoscopy looks at all of it. For people at average risk with no symptoms, it is still an accepted screening option, especially when repeated on schedule or paired with a yearly stool test.
How often should it be repeated?
Guideline bodies suggest every five years if it is clear, or every ten years when a FIT stool test is also done every year. Any adenoma found changes the plan. Your doctor sets the gap on what was seen and your own risk.
Can it find cancer?
It can find a growth in the part it reaches and take a sample. Only the laboratory report on that sample can say whether it is cancer. A clear sigmoidoscopy cannot rule out cancer in the upper colon, and it never rules it out when symptoms are present.
What are the risks?
They are small. Some people notice a little bleeding, especially after a polyp is removed. A tear in the bowel wall is rare. Go to an emergency department the same day if you have severe belly pain, heavy bleeding or a fever after the test.
Can I go to work the same day?
Usually, yes. Without sedation most people go back to normal activity soon after the test. If you were given sedation, someone must take you home and you should rest for the rest of the day. Ask the centre which applies before you book.
Is sigmoidoscopy easy to get in Hyderabad?
It is offered at gastroenterology centres, though fewer people choose it for screening than a full colonoscopy. CION does not perform the test itself. CION arranges it at an accredited partner and the report comes back to your CION doctor for review.
Does insurance or Aarogyasri pay for it?
Screening in people with no symptoms is often not covered by schemes or by most insurance policies. Cover is more likely when a test is ordered for a symptom. Ask the centre for a written quote and check your policy before the test, not after.
Your Specialists
Meet CION's colon cancer specialists. Bring your colonoscopy, scan or biopsy report.
Our surgical and medical oncologists plan colon cancer care together: which operation, whether chemotherapy is needed, and the follow-up that comes after.
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Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
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Sources
- American Cancer Society — Colorectal Cancer Screening Tests
- National Cancer Institute — Screening Tests to Detect Colorectal Cancer and Polyps
- US Preventive Services Task Force — Recommendation: Colorectal Cancer: Screening
- National Cancer Institute — Colorectal Cancer Screening
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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Tell us your age, any symptoms and your family history. A CION doctor will explain which screening test makes sense and arrange it with an accredited partner. One helpline serves every CION centre.