A colonoscopy is a medical procedure that provides a detailed internal view of the large intestine, including the colon and rectum. Its primary purpose is the early detection and prevention of colorectal cancer by identifying and removing precancerous growths called polyps. Medical organizations have recently updated their recommendations based on new data showing a rise in cancer incidence among younger adults, meaning screening now begins earlier than in past decades.
Guidelines for Standard-Risk Individuals
Current medical guidelines establish a definitive starting age for individuals considered to be at standard risk for developing colorectal cancer. The American Cancer Society and the U.S. Preventive Services Task Force now recommend that all average-risk adults begin regular screening at age 45. This updated recommendation moved the starting age five years earlier than the previous standard of age 50, reflecting the increasing rates of colorectal cancer in younger populations.
A person is considered to be at standard risk if they do not have a personal history of inflammatory bowel disease, prior polyps, or colorectal cancer. Additionally, standard risk means there is no known family history of colorectal cancer or a confirmed genetic syndrome that predisposes them to the disease. For these individuals, a colonoscopy is recommended every 10 years if the results are normal, as polyps typically take a decade or longer to develop into malignant tumors. For those in good health, screening should continue until age 75, with the decision to continue until age 85 based on individual health status and prior screening history.
When to Consider Earlier Screening
Certain factors elevate a person’s risk beyond the standard threshold, which necessitates beginning the screening process before age 45. A strong family history is one of the most common reasons for an earlier start, particularly if a first-degree relative, such as a parent or sibling, was diagnosed with colorectal cancer or advanced polyps. The general rule of thumb in this situation is to start screening at age 40, or 10 years younger than the age at which the relative was diagnosed, whichever is earlier. For example, if a parent was diagnosed at age 45, the child should begin screening at age 35.
A personal history of inflammatory bowel disease (IBD), which includes Crohn’s disease or ulcerative colitis, also significantly increases risk. These conditions cause chronic inflammation in the colon lining, and screening is typically advised eight to ten years after the onset of IBD symptoms. Individuals with confirmed genetic syndromes face the highest risk and require the earliest and most frequent screening. Those with Familial Adenomatous Polyposis (FAP) may need to begin colonoscopies as early as age 10, while individuals with Lynch syndrome usually start at age 25.
Understanding the Colonoscopy Procedure
For many people, the most challenging part of the process is the bowel preparation, which ensures the colon is clean for clear visibility. This multi-step prep usually begins a few days before the procedure, involving a low-fiber diet that avoids foods with residue like nuts and seeds. The day before the colonoscopy, the patient must switch to a clear-liquid diet and begin taking a prescribed laxative solution that flushes the colon. The goal of this preparation is to achieve a bowel movement that is clear and liquid, which allows the physician to thoroughly examine the lining.
The procedure itself typically takes between 30 and 60 minutes and is usually performed in an outpatient setting. A healthcare professional inserts an intravenous (IV) line to administer a sedative or anesthesia, which ensures the patient is relaxed and comfortable, often with no memory of the procedure. The physician then inserts a long, flexible tube called a colonoscope through the rectum and advances it through the entire colon. The scope contains a light and a video camera that transmits images to a monitor, allowing the doctor to search for abnormalities.
If the physician finds a polyp, a small electrical current is used to remove it with a wire loop, a procedure called a polypectomy. Because the colon lining does not have pain-sensing nerves, this removal is painless, but it is a preventive step, as most cancers begin as a polyp. Following the procedure, the patient rests in a recovery area for about an hour until the effects of the sedative wear off. Due to the sedation, a ride home is necessary, and no driving is allowed for 24 hours.
Alternatives to Traditional Colonoscopy Screening
While colonoscopy is considered the gold standard for screening, there are other accepted methods available for average-risk individuals. These alternatives generally require more frequent testing, and if any test returns a positive result, a full colonoscopy is still required for follow-up.
Alternative Screening Methods
- Stool-based tests, such as the Fecal Immunochemical Test (FIT) and the multi-targeted stool DNA test, which analyze samples collected at home for signs of blood or specific DNA changes.
- Flexible sigmoidoscopy, which uses a shorter scope to examine only the rectum and lower third of the colon.
- CT colonography, often called a virtual colonoscopy, which uses a computed tomography scan.
The ability of the colonoscopy to be both diagnostic—finding the problem—and therapeutic—removing polyps immediately—is why it remains the most comprehensive screening option.