The prostate is a walnut-sized gland in the male reproductive system, located just below the urinary bladder and in front of the rectum. It surrounds the urethra and produces fluid that forms part of semen. On ultrasound, the prostate can be evaluated transabdominally (through the lower abdomen with a full bladder) or transrectally (TRUS), with the transrectal approach providing much higher-resolution images. The normal prostate has a heterogeneous echotexture with distinct zones — the peripheral zone, transition zone, and central zone. Ultrasound is used to measure prostate volume (important for evaluating benign prostatic hyperplasia), detect suspicious lesions, and guide biopsy for prostate cancer diagnosis. Post-void residual measurement is often performed alongside prostate evaluation.