Testis

The testis (plural: testes) is the male gonad, an oval-shaped gland located within the scrotum that produces sperm and the hormone testosterone. On ultrasound, the normal testis appears as a homogeneous, medium-echogenicity structure with a smooth contour, and the mediastinum testis (a fibrous band running along its posterior aspect) appears as a bright echogenic line. Scrotal ultrasound is the primary imaging modality for evaluating testicular abnormalities, including masses (benign and malignant), torsion, epididymitis/orchitis, hydrocele, varicocele, undescended testis, and trauma. Sonographers assess both testes for symmetry in size and echogenicity, and color Doppler evaluates blood flow — particularly critical in the emergency evaluation of acute scrotal pain where torsion must be distinguished from infection.