Flexible Sigmoidoscopy Test: Purpose, Test Details & Results

Purpose of Flexible Sigmoidoscopy Test

Flexible sigmoidoscopy is a minimally invasive procedure used to examine the lower part of the colon and rectum. Its primary role is in the early detection and prevention of colorectal cancer, but it also helps diagnose other bowel conditions. With colorectal cancer being among the most common cancers worldwide, screening tools like flexible sigmoidoscopy have become crucial in reducing disease incidence and mortality, often catching problems before symptoms develop.

Table 1: Main Purposes of Flexible Sigmoidoscopy

Early Detection and Prevention of Colorectal Cancer

Flexible sigmoidoscopy is a proven tool in reducing both the incidence and mortality of colorectal cancer. Large randomized trials have shown that a single flexible sigmoidoscopy screening can reduce colorectal cancer diagnoses by 18%–31% and mortality by up to 50% in the distal colon, with long-lasting effects for at least 17 years after screening 1, 10, 11, 12. This impact is most pronounced for cancers in the lower (distal) colon and rectum, where the test is most effective.

Diagnosis of Bowel Symptoms

Beyond cancer screening, flexible sigmoidoscopy is also valuable for investigating unexplained gastrointestinal symptoms. It can help identify the cause of rectal bleeding, chronic diarrhea, unexplained weight loss, or abdominal pain. For example, it is particularly useful in diagnosing conditions like pseudomembranous colitis when standard stool tests are inconclusive 3.

Prevention Through Polyp Removal

During the procedure, doctors can remove precancerous polyps (adenomas). This immediate intervention prevents some polyps from developing into colorectal cancer, providing a direct preventative benefit 10, 11, 12.

Monitoring High-Risk Individuals

Flexible sigmoidoscopy is also used in the follow-up of patients with a history of polyps, colorectal cancer, or chronic inflammatory bowel disease, to ensure that new growths or recurrences are detected early 6.

Flexible Sigmoidoscopy Test Details

Understanding what happens during a flexible sigmoidoscopy helps to ease anxiety and prepare for the test. It’s typically performed in an outpatient setting and is less invasive than a full colonoscopy, generally requiring less preparation and no sedation.

Table 2: Flexible Sigmoidoscopy Test Steps and Experience

Preparation for the Test

• Bowel Cleansing: Patients are usually asked to clear the lower colon with enemas or a mild laxative before the procedure. Unlike colonoscopy, a complete bowel prep is not necessary, making preparation less burdensome 6, 7.
• Dietary Restrictions: Sometimes, a light diet the day before the test is recommended.
• No Sedation Required: Most flexible sigmoidoscopies are done without sedation, allowing for a quick recovery 9.

The Procedure

• How It’s Performed: The doctor inserts a thin, flexible tube (sigmoidoscope) with a light and camera into the rectum and sigmoid colon (the last part of the colon). Air may be introduced to expand the colon for better viewing.
• What’s Examined: The test inspects the rectum and lower (distal) colon (about the last 60 cm of the large bowel) for polyps, cancer, inflammation, or other abnormalities 6.
• Polyp Removal or Biopsy: If abnormalities or polyps are found, small instruments passed through the scope can remove them or take tissue samples.

Patient Experience

• Discomfort Level: Most patients experience mild cramping or pressure. Pain is reported more often by women; up to 22% of women report pain compared to 5% of men, which can impact willingness to repeat the test 9.
• Duration: The procedure usually takes 10–20 minutes and is done on an outpatient basis 6, 9.
• Aftercare: Most people can resume normal activities immediately. Minor bloating or gas is possible for a few hours.

Risks and Complications

• Safety Profile: Flexible sigmoidoscopy is very safe. Serious complications (e.g., perforation or significant bleeding) are rare, occurring in less than 0.1% of cases 2, 7.
• Adverse Events: Minor discomfort is the most common issue. Major complications are extremely rare but may include bleeding or, very rarely, bowel perforation.

Flexible Sigmoidoscopy Test Results & Follow-Up

The results of a flexible sigmoidoscopy can range from an all-clear to the discovery of benign polyps, inflammatory changes, or cancer. Understanding what your results mean and what happens next is crucial for effective care.

Table 3: Interpreting Flexible Sigmoidoscopy Results

What the Results Mean

• Normal Result: If no abnormalities are found, the risk of colorectal cancer in the next decade is significantly reduced. Routine screening intervals will be recommended based on age and risk factors 10, 12.
• Polyps Detected: Most polyps found are adenomas, which are benign but have the potential to become cancerous. These are typically removed during the procedure. If numerous or large polyps are found, a full colonoscopy may be recommended to examine the entire colon 6, 10.
• Inflammation or Colitis: The presence of inflammation, ulcers, or signs of diseases such as ulcerative colitis or pseudomembranous colitis will prompt further investigation or targeted treatment 3, 6.
• Suspicious or Cancerous Lesion: If a suspicious mass or cancer is detected, referral for a full colonoscopy and biopsy is urgent, often followed by further imaging and multidisciplinary evaluation 6, 10, 12.

Next Steps and Follow-Up

• Routine Follow-Up: For those with a normal exam, re-screening intervals are typically every 5–10 years, depending on guidelines and individual risk 12.
• Further Testing: Positive findings (polyps, suspicious lesions) usually require follow-up colonoscopy to examine the entire colon and remove any additional polyps or take biopsies for diagnosis 6, 10.
• Treatment: If colorectal cancer is confirmed, early detection via flexible sigmoidoscopy means treatment can often start at an earlier, more treatable stage. Most cancers found through screening are at stage I or II, which have higher cure rates 6, 10.
• Combined Screening Approaches: Some guidelines recommend combining flexible sigmoidoscopy with fecal occult blood testing (FOBT) or fecal immunochemical tests (FIT) for improved detection, especially for cancers in the proximal (upper) colon that sigmoidoscopy may miss 8.

Impact on Long-Term Outcomes

• Reduced Cancer Incidence and Mortality: Multiple large studies confirm that flexible sigmoidoscopy screening significantly reduces both the number of new colorectal cancer cases and deaths, especially for cancers in the lower colon and rectum 1, 10, 11, 12.
• Effectiveness by Age and Sex: The benefit is greatest in men and women under 60, with somewhat less impact in women over 60, likely due to more cancers developing in the upper colon in this group 5.
• Patient Satisfaction and Adherence: Most patients find the test acceptable, though willingness to repeat is higher with noninvasive tests like FIT. Pain management and clear communication can improve adherence rates, especially among women 9.

Conclusion

Flexible sigmoidoscopy is a powerful tool for the early detection and prevention of colorectal cancer, as well as for diagnosing other lower bowel conditions. Its effectiveness, safety, and relatively simple preparation make it a valuable option for many individuals, especially as part of a broader screening program.

Key takeaways:

• Flexible sigmoidoscopy reduces colorectal cancer incidence and mortality.
• It is most effective in detecting and preventing cancers in the distal (lower) colon and rectum.
• The procedure is quick, minimally invasive, and generally well-tolerated, though some discomfort is possible.
• Most findings (such as polyps) can be managed during the test; suspicious lesions require further evaluation.
• The test is especially beneficial for men and women under 60; alternative or additional tests may be considered for older women.
• Combining flexible sigmoidoscopy with FIT or FOBT can increase cancer detection rates.
• Ongoing communication and support can improve patient experience and adherence to screening recommendations.

Flexible sigmoidoscopy remains a cornerstone of colorectal cancer prevention strategies, offering significant benefits for both individuals and public health.