A TRUS-guided biopsy (Transrectal Ultrasound-guided biopsy) is a medical procedure used to diagnose prostate cancer. During this test, a small ultrasound probe is inserted into the rectum to create real-time images of the prostate. These images help guide the doctor as they insert a needle through the rectal wall and into the prostate gland to collect tissue samples. These samples are then analyzed in a lab to determine the presence or absence of cancer cells.