Screening tests are designed to detect colorectal cancer or precancerous changes before symptoms appear.
Different tests have different advantages and limitations. The most suitable option depends on a person's age, medical history, risk level, preferences, and local availability.
Colonoscopy
Colonoscopy allows a doctor to examine the lining of the entire colon and rectum using a flexible tube with a small camera.
It is particularly valuable because it can both identify and remove many polyps during the same procedure.
If a polyp is found, the doctor may remove it using a small instrument passed through the colonoscope. The tissue is then sent to a laboratory for microscopic examination.
The procedure generally requires bowel preparation beforehand so that stool does not obscure the view.
Depending on the patient's circumstances and the medical facility, sedation may be offered.
Possible complications include bleeding, particularly after removal of a larger polyp, and rarely, perforation of the bowel. The medical team considers these risks alongside the potential benefits.
Fecal Immunochemical Test (FIT)
FIT looks for small amounts of human blood in a stool sample.
It can be completed at home and is generally more convenient than an invasive examination. It is often used as a regular screening option for people at average risk.
However, FIT does not directly identify or remove polyps. Some polyps do not bleed, so a negative result does not guarantee that no precancerous growth is present.
A positive FIT result requires follow-up colonoscopy.
Fecal Occult Blood Testing
Traditional fecal occult blood tests look for hidden blood in stool.
Some versions use chemical reactions to detect blood, while FIT uses antibodies that recognize human hemoglobin.
The exact preparation requirements and recommended testing interval depend on the specific test.
Like FIT, a negative result does not rule out every polyp.
Stool DNA Testing
Multitarget stool DNA tests look for certain abnormal DNA markers as well as blood in a stool sample.
These tests may detect some cancers and advanced precancerous lesions that a blood-only stool test might miss.
They are not perfect, however. False-positive and false-negative results can occur, and an abnormal result requires colonoscopy.
Flexible Sigmoidoscopy
Flexible sigmoidoscopy uses a thin, flexible instrument to examine the rectum and lower part of the colon.
It can identify polyps and other abnormalities in the area examined. However, it does not inspect the entire colon.
If an abnormality is found, a full colonoscopy may be recommended.
CT Colonography
CT colonography, sometimes called virtual colonoscopy, uses computed tomography to create images of the colon.
It does not involve inserting a camera through the entire colon in the same way as conventional colonoscopy, but bowel preparation is usually still required.
If the scan identifies a polyp that needs removal, the patient will generally need a conventional colonoscopy.
The choice between screening methods should be made with a healthcare professional. A test that someone is willing and able to complete regularly may be more useful than a preferred test that is repeatedly postponed.
6. When Should You Begin Colorectal Cancer Screening?
There is no single starting age that applies to every person in every country.
For example, the American Cancer Society's 2026 guidance recommends regular screening beginning at age 45 for adults at average risk. It lists options including annual high-sensitivity stool tests, stool DNA testing at specified intervals, colonoscopy every 10 years, CT colonography every 5 years, and flexible sigmoidoscopy every 5 years. <sup>[1]</sup>
The US Centers for Disease Control and Prevention also states that most average-risk adults should begin screening at 45. <sup>[2]</sup>
These are US recommendations, not automatic rules for every country or every patient.
People with a family history, previous advanced polyps, inflammatory bowel disease, or inherited cancer syndromes may need to begin earlier and follow a different schedule.
After a polyp is removed, the next colonoscopy interval depends on the number, size, type, and microscopic features of the polyps, as well as the quality of the examination and whether removal was complete.
For this reason, patients should not assume that everyone needs a colonoscopy every 10 years. That interval is generally associated with a normal, high-quality colonoscopy in an average-risk person, not every possible clinical situation.
7. What Happens After a Polyp Is Found?
Discovering a polyp does not mean that a person has cancer.
Many polyps can be removed during colonoscopy, and most are not invasive cancer.
After removal, the tissue is sent to a laboratory for pathology testing. The report helps determine the next step.
Doctors generally consider:
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The number of polyps.
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The size of the largest polyp.
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Whether the polyp is an adenoma, serrated lesion, or another type.
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Whether dysplasia is present.
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Whether the polyp was completely removed.
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Whether the colonoscopy was complete and the bowel preparation was adequate.
A person with one or two small, low-risk adenomas may have a different follow-up schedule from someone with multiple large adenomas or a lesion containing high-grade dysplasia.
Some large or complex polyps cannot be safely removed using routine techniques. They may require advanced endoscopic removal or, in selected cases, surgery.
If pathology shows invasive cancer, additional evaluation is needed to determine how deeply the cancer has grown and whether it has spread. Treatment may involve surgery and, depending on the stage and tumor characteristics, chemotherapy, radiation, or other therapies.
The important point is that a polyp finding should lead to a clear follow-up plan rather than unnecessary panic.
8. Eating Habits That Support Colorectal Health
No food can guarantee protection against colorectal cancer. However, a balanced dietary pattern can support general health and may help reduce colorectal cancer risk.
Eat More Fiber-Rich Foods
Dietary fiber is found in vegetables, fruits, beans, lentils, nuts, seeds, and whole grains.
Fiber helps support regular bowel movements and contributes to a healthy digestive environment.
Examples include:
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Oats and whole-grain bread.
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Brown rice and other whole grains.
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Beans, lentils, and chickpeas.
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Broccoli, carrots, leafy greens, and other vegetables.
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Apples, pears, oranges, and berries.
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Nuts and seeds.
Increase fiber gradually, especially if your usual diet contains very little. A sudden large increase may cause bloating or gas.
Adequate fluid intake also helps fiber work comfortably in the digestive system.
Limit Processed Meat
Processed meats include products such as bacon, ham, sausages, hot dogs, and some preserved meat products.
Regular consumption of processed meat is associated with an increased risk of colorectal cancer.
This does not mean that one serving will cause cancer. Risk is related to patterns of consumption over time.
Reducing processed meat and choosing a wider variety of protein sources can be a practical change.
Moderate Red Meat Consumption
Red meat includes beef, pork, and lamb.
People do not necessarily need to eliminate all red meat, but limiting frequent or large portions and choosing other protein sources can support a balanced diet.
Fish, poultry, beans, lentils, tofu, and nuts can all contribute to dietary variety.
Choose a Variety of Plant Foods
Different fruits and vegetables provide different nutrients and types of fiber.
Rather than relying on a single so-called superfood, aim for variety across the week.
Colorful vegetables, leafy greens, legumes, and whole grains can form the foundation of everyday meals.
9. Physical Activity and Weight Management
Regular physical activity is associated with a lower risk of colorectal cancer.
Exercise supports healthy body weight, cardiovascular health, insulin regulation, and overall metabolic function.
You do not need to begin with intense workouts.
Practical options include: