Flexible Sigmoidoscopy — Targeted Examination
A flexible sigmoidoscopy is similar to a colonoscopy but only examines the lower third of the colon (the rectum and sigmoid colon).
Because many cancers occur in the lower colon, this can be an effective screening tool, often performed every 5 years or every 10 years if combined with an annual FIT. Its primary drawback is that it may miss polyps located in the upper two-thirds of the colon.
As of 2026, blood-based screening (sometimes called "liquid biopsies") is gaining traction for patients who are unable or unwilling to undergo traditional exams. These tests look for circulating tumor DNA (ctDNA) or specific proteins like Septin 9.
While highly convenient, blood tests are currently less effective at finding precancerous polyps compared to a colonoscopy. They are primarily used to detect existing cancer and are not yet considered a full replacement for visual exams in most clinical guidelines.