A colonoscopy examines the lining of the large intestine (colon) for abnormalities. Surveillance colonoscopy is a targeted procedure performed on individuals at an elevated risk for developing colorectal cancer. This heightened risk is typically due to a personal history of precancerous growths or certain chronic conditions. It is a specialized monitoring tool for those already identified as having an increased cancer risk, not a routine check for the general population.
Distinguishing Surveillance from Standard Screening
Standard screening colonoscopy is intended for asymptomatic individuals at average risk for colorectal cancer. The goal is to prevent cancer by detecting and removing precancerous lesions (polyps) before they become malignant. For those with no personal or family history of polyps or cancer, the typical screening interval is once every 10 years.
Surveillance colonoscopy is performed on patients who already have a history of polyps, colorectal cancer, or a predisposing condition. Its purpose shifts from primary prevention to secondary prevention and early detection of recurrence or new lesions in a high-risk setting. Because these individuals are not average-risk, the procedure is performed at much shorter, more frequent intervals than the standard 10-year period.
Patient History Requiring Surveillance
A personal history of certain findings during a previous colonoscopy is the most common reason for a patient to be placed on a surveillance protocol. Specifically, the removal of adenomatous polyps or sessile serrated lesions requires ongoing monitoring due to their potential to progress into cancer. The risk level, and thus the surveillance frequency, is determined by specific characteristics of the removed polyps, such as their size, number, and cellular makeup.
History of Adenomatous Polyps
Adenomas are classified as high-risk, or advanced, based on features found by the pathologist. High-risk features include an adenoma size of 10 millimeters or larger, the presence of three or more adenomas, or advanced cellular architecture. Lesions exhibiting high-grade dysplasia (severely abnormal cells) or villous features (a specific, finger-like growth pattern) are also considered advanced. Patients with these findings are placed on an accelerated surveillance schedule to quickly identify any new precancerous tissue.
Previous Colorectal Cancer
After surgical removal of colorectal cancer, surveillance colonoscopies look for local recurrence or the development of new, unrelated cancers (metachronous lesions). The initial follow-up colonoscopy is typically performed within one year after surgery to ensure all disease was removed. This intensive monitoring is necessary because a previous cancer diagnosis significantly increases the lifetime risk of developing another primary tumor.
Inflammatory Bowel Disease (IBD)
Individuals with long-standing, extensive ulcerative colitis or Crohn’s disease involving the colon are at an elevated risk for developing colorectal cancer due to chronic inflammation. Surveillance colonoscopy is recommended to begin eight to 10 years after the onset of symptoms for these patients. The goal is to detect dysplasia, the precursor to cancer, in the chronically inflamed lining of the colon.
Genetic Syndromes
Certain inherited genetic conditions cause a high lifetime risk of colorectal cancer, necessitating early surveillance. Familial Adenomatous Polyposis (FAP) and Lynch Syndrome are examples where patients often begin colonoscopies at a young age, sometimes in their teenage years. Due to the rapid progression of polyps in FAP or the nature of cancer development in Lynch Syndrome, surveillance intervals are often the shortest, sometimes occurring every one to two years.
Establishing the Follow-Up Schedule
The interval between surveillance colonoscopies is not fixed but is determined by the physician based on the specific findings of the most recent procedure. Guidelines from medical societies provide a framework, but the final schedule is individualized. The most significant factor influencing the next procedure’s timing is the pathology report from the polyps removed during the last examination.
If a patient had only one or two small, non-advanced adenomas, they may be advised to have their next colonoscopy in five to 10 years. However, finding high-risk adenomas (such as three to 10 polyps or any polyp with advanced features) typically shortens the follow-up interval to three years. For patients with extensive inflammatory bowel disease, surveillance procedures are often scheduled every one to three years, depending on the extent of the disease and prior findings. Adherence to this schedule is important for the effectiveness of the surveillance strategy in reducing the risk of cancer progression.