A colonoscopy is a medical procedure that uses a flexible tube with a camera to examine the entire large intestine (colon) and rectum. Its primary purpose is to screen for and prevent colorectal cancer by detecting and removing abnormal growths called polyps, which can develop into cancer. It also helps identify issues like irritated tissues, ulcers, or sources of bleeding.
Standard Screening Guidelines
For individuals at average risk of colorectal cancer, current guidelines recommend initiating regular colonoscopy screening at age 45. This recommendation is based on the rising incidence of colorectal cancer in younger adults and the comparable yield of advanced colorectal neoplasia in those aged 45-49 to older screening cohorts. This interval applies to asymptomatic individuals who do not have specific risk factors or a family history of colorectal cancer.
Factors Affecting Screening Frequency
Several individual risk factors can necessitate earlier or more frequent colonoscopy screenings than the standard guidelines. A significant factor is a personal or family history of colorectal cancer or advanced polyps, particularly in a first-degree relative (parent, sibling, or child). If a first-degree relative was diagnosed with colorectal cancer before age 60, or if there are two first-degree relatives diagnosed at any age, screening may begin at age 40, or 10 years before the earliest diagnosis in the family, whichever comes first. More frequent screenings, potentially every three to five years, may be recommended.
Individuals diagnosed with inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis, also face an increased risk of colorectal cancer. Colonoscopy surveillance typically begins 8 to 10 years after the onset of IBD symptoms, with follow-up procedures recommended every one to three years, depending on the extent of the disease and other risk factors. The risk of developing colorectal cancer in IBD patients depends on the severity and duration of the condition, as well as factors like family history of bowel cancer.
Certain inherited genetic syndromes significantly elevate colorectal cancer risk, leading to very early and frequent screening recommendations. For instance, individuals with Lynch syndrome may begin colonoscopy screening as early as 20-25 years of age, with subsequent screenings typically performed every one to two years. Similarly, familial adenomatous polyposis (FAP) often requires colonoscopy screening to start as early as age 10, with annual or biennial frequency due to the high likelihood of developing numerous polyps. These intensive surveillance schedules are crucial for early detection and intervention in these high-risk populations.
Follow-Up Based on Colonoscopy Findings
The findings from a colonoscopy directly influence the timing of subsequent procedures. If no polyps or abnormalities are found, the follow-up interval is typically 10 years.
When polyps are found, their type, size, and number determine the recommended surveillance interval. Small hyperplastic polyps (generally less than 10 mm and located in the rectosigmoid colon) are considered low risk and typically do not alter the 10-year follow-up schedule. However, hyperplastic polyps 10 mm or larger, especially those found in the proximal colon, may warrant a shorter follow-up, often within three to five years, as they can be associated with a higher risk of neoplasia.
Precancerous polyps, such as adenomas and sessile serrated lesions (SSLs), require closer surveillance.
Adenomas
One to two small tubular adenomas (less than 10 mm) completely removed: Follow-up in seven to 10 years.
Three to four small adenomas: Interval shortens to three to five years.
Five to 10 adenomas: Three-year follow-up.
More than 10 adenomas: Repeat colonoscopy in one year, with consideration for genetic assessment.
Larger adenomas (10 mm or more), or those with villous features or high-grade dysplasia: Three-year follow-up.
Sessile Serrated Polyps (SSPs)
One to two small SSPs (less than 10 mm) without dysplasia: Five to 10-year follow-up.
Larger SSPs (10 mm or more) or those with dysplasia: Three-year interval.
If polyp removal was incomplete, an earlier repeat colonoscopy (often within three to six months) may be advised to ensure complete eradication of the tissue.