Regular screening programs are of great importance for the early diagnosis of rectal cancer. For individuals without any risk factors, starting routine screenings at age 50 is critically important for early detection. For individuals with risk factors, the screening age can be set earlier. Frequently, rectal cancer is diagnosed during examinations prompted by symptoms such as rectal bleeding or unexplained iron deficiency anemia.

Colonoscopy is the most commonly used method for screening programs and definitive diagnosis. During a colonoscopy, small tissue samples (biopsies) are taken from suspicious areas. Pathological examination of these biopsy samples in the laboratory is the fundamental step in confirming a diagnosis of rectal cancer.