A colonoscopy is a medical procedure using a flexible tube (colonoscope) equipped with a camera to examine the full length of the large intestine, including the colon and rectum. This examination focuses on detecting and removing precancerous growths known as polyps. By excising these polyps before they develop into cancer, a colonoscopy actively reduces the risk of colorectal cancer. It is considered the most comprehensive method for screening the entire colon lining.
Understanding Screening Guidelines
Current medical guidelines recommend that individuals at average risk for colorectal cancer begin regular screening at age 45. This shift from age 50 responds to the rise in colorectal cancer incidence among younger adults. An individual is considered at average risk if they have no personal history of colorectal cancer or certain polyps, no family history of the disease, and no personal history of inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis.
If the initial colonoscopy is clear and no polyps are found, the recommended interval for the next screening is typically ten years. However, certain risk factors necessitate starting screening earlier or undergoing more frequent examinations. Significant factors include a personal or strong family history of colorectal cancer or advanced polyps in a first-degree relative (a parent, sibling, or child).
For those with an affected first-degree relative, screening is advised to begin at age 40 or ten years before the age the family member was diagnosed, whichever occurs first. Other conditions requiring earlier and more frequent screening include a history of IBD or a diagnosed hereditary syndrome, such as Lynch syndrome or familial adenomatous polyposis (FAP). The specific screening frequency for high-risk individuals, which may be every one to five years, is determined by the physician based on findings and risk profile.
Preparing for the Procedure
The most challenging aspect of a colonoscopy is the preparation required to ensure the colon is completely clean for accurate results. A few days before the procedure, patients switch to a low-fiber diet, avoiding whole grains, nuts, seeds, and raw fruits and vegetables. This dietary change reduces residue in the digestive tract.
The day before the procedure, a strict clear liquid diet must be followed, consisting only of items like water, clear broth, clear juices without pulp, and gelatin. No solid food or opaque liquids are permitted, as the goal is to fully empty the colon. The final step is consuming a prescribed laxative solution, known as the bowel prep, usually split into two doses.
The first dose is often taken the evening before, and the second is taken several hours before the appointment on the day of the procedure. This laxative regimen causes significant diarrhea to flush out all fecal material, which is necessary for the doctor to clearly visualize the entire colon lining. If the preparation is inadequate, the procedure may need to be rescheduled because polyps or lesions could be missed.
What Happens During and Immediately After
On the day of the procedure, most patients receive sedation or light anesthesia to ensure comfort and minimize awareness. The sedative is typically administered intravenously, allowing the patient to relax deeply or fall asleep. Once sedated, the doctor gently inserts the colonoscope through the rectum and advances it through the entire colon up to the junction with the small intestine.
To get a better view of the colon walls, the doctor introduces air or carbon dioxide to inflate the colon. The camera on the scope transmits a real-time video image to a monitor, allowing the physician to inspect the colon lining for abnormalities. If a polyp is found, it is immediately removed using specialized tools passed through the scope in a procedure called a polypectomy.
Following the 30- to 60-minute procedure, the patient is moved to a recovery area where the effects of the sedation wear off. Mild cramping or bloating is common due to the air introduced, which usually passes quickly as the body expels the gas. Due to the lingering effects of the sedative, a friend or family member must drive the patient home. The patient is advised to avoid driving or making significant decisions for the rest of the day. The doctor provides initial findings immediately, and the results of any biopsies taken are typically communicated within a few days.
Other Screening Options
While colonoscopy is the most thorough screening method because it allows for immediate polyp removal, several less invasive alternatives are available. Stool-based tests are a popular category of alternatives that can often be performed at home.
The Fecal Immunochemical Test (FIT) detects hidden blood in the stool, which can be an early sign of cancer or large polyps, and is typically done annually. Similarly, the high-sensitivity guaiac-based Fecal Occult Blood Test (gFOBT) also looks for traces of blood. Another option is the stool DNA test, such as Cologuard, which analyzes the sample for hidden blood and specific DNA markers associated with polyps and cancer.
A positive result from any stool-based test is not a cancer diagnosis but indicates a need for further investigation. A follow-up diagnostic colonoscopy is required to locate the source of the blood or abnormal DNA and to remove any precancerous growths. Other structural exams include CT Colonography (virtual colonoscopy) and Flexible Sigmoidoscopy, which only examines the lower third of the colon.
Screening for colorectal cancer is one of the most effective ways to prevent the disease or catch it at its earliest, most treatable stage. The decision of when to begin screening is based on your individual risk profile, including age, personal medical history, and family history. Discussing these factors with your healthcare provider helps determine the most appropriate starting age and screening method.