Can rectal ultrasound detect it? When we perform an abdominal ultrasound for the digestive system, we might see a potential mass in the abdomen, but its specific nature cannot be clearly identified. Therefore, the definitive diagnosis of rectal cancer still relies on biopsy and pathological examination. Thus, it is recommended to go to the hospital and consult a professional oncologist for tests, such as undergoing an endoscopic biopsy or having a surgical procedure to remove and then analyze the pathology to confirm whether it is rectal cancer or not.