How is colorectal cancer diagnosed?

To find the cause of symptoms, the doctor evaluates one's personal and family medical history. The doctor also performs a physical exam and may order one or more diagnostic tests. These may include a blood test called a CEA assay to measure a protein called carcinoembryonic antigen that is sometimes higher in patients with colorectal cancer. The doctor may also order x-rays of the gastrointestinal tract , sigmoidoscopy , or colonoscopy. If abnormal tissue is found during these tests, a biopsy (the removal of tissue for examination under a microscope by a pathologist) is performed to determine if a person has cancer.

If the diagnosis is cancer, the doctor will want to learn the stage (or extent) of disease. Staging is a careful attempt to find out whether the cancer has spread and, if so, to what parts of the body. Knowing the stage of the disease helps the doctor plan treatment. Additional tests may be performed to help determine the stage.