A colonoscopy uses a long, flexible tube equipped with a camera, called a colonoscope, to examine the entire large intestine (colon) and the rectum. Performed while the patient is sedated, the procedure allows a doctor to visually inspect the inner lining of the bowel wall for abnormalities. The purpose of the colonoscopy is to provide a complete assessment of colorectal health, making it the most comprehensive tool for both the detection and prevention of colorectal disease.
Detecting and Removing Pre-Cancerous Growths
The primary benefit of a colonoscopy is its ability to prevent colorectal cancer. Cancer typically develops from small, abnormal growths on the lining of the colon called polyps. The most common type is the adenomatous polyp, or adenoma, which can take many years to progress into cancer.
The procedure is therapeutic because it allows for the immediate removal of these polyps during the same session, a process known as a polypectomy. This dual function, finding a potential problem and eliminating it instantly, distinguishes the colonoscopy from other screening tests. Removing these benign adenomas effectively interrupts the cancer development pathway and reduces the chance of death from colorectal cancer.
Investigating Symptoms and Other Gastrointestinal Issues
Beyond its role as a preventative screening tool, a colonoscopy is used as a diagnostic procedure to investigate unexplained gastrointestinal symptoms. It is recommended for individuals experiencing persistent changes in bowel habits, chronic abdominal pain, or unexplained iron deficiency anemia. The procedure provides a direct visual examination of the lower digestive tract that cannot be achieved otherwise.
A colonoscopy can help identify the source of rectal bleeding or persistent diarrhea. The doctor can also use the scope to take small tissue samples, or biopsies, which are analyzed to confirm a diagnosis. This capability allows for the diagnosis of various inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis, as well as diverticulosis and infectious colitis.
Current Screening Age and Frequency Recommendations
For individuals considered at average risk for colorectal cancer, current guidelines recommend beginning routine screening at age 45. This age was lowered from 50 due to a rise in colorectal cancer incidence among younger adults. If an initial colonoscopy is normal and no polyps are found, the patient is advised to repeat the procedure every ten years.
A different schedule is necessary for high-risk patients, whose factors include a strong family history of colorectal cancer, a personal history of inflammatory bowel disease, or certain hereditary genetic syndromes. For those with a first-degree relative diagnosed with colorectal cancer before age 60, screening starts at age 40 or ten years earlier than the relative’s diagnosis, whichever is first. Surveillance frequency is increased for high-risk individuals, sometimes requiring the test every one to five years, depending on their specific risk factors and previous findings.
Comparing Colonoscopy to Alternative Screening Methods
While colonoscopy remains the most effective screening method, other tests are available for average-risk individuals unable or unwilling to undergo the full procedure. Alternatives include stool-based tests (FIT and stool DNA tests) which look for blood or genetic markers of cancer, and visual exams like flexible sigmoidoscopy and CT colonography (virtual colonoscopy).
The primary advantage of the colonoscopy is its ability to inspect the entire colon and immediately remove pre-cancerous polyps, a capability stool-based tests lack. Flexible sigmoidoscopy only examines the lower third of the colon, potentially missing lesions in the upper sections. For all non-colonoscopy screening methods, a positive result necessitates a follow-up colonoscopy to confirm the finding and allow for tissue removal.