The purpose of this pictorial essay is to describe the ultrasonographic and clinical findings of patients with small testes due to a wide range of causes. We retrospectively reviewed the ultrasonographic and clinical findings of various causes of small testes. We present various causes of small testes on ultrasonography including Klinefelter syndrome, testicular torsion, mumps orchitis, inguinal hernia, cryptorchidism, varicocele, and trauma. On ultrasonography, small testes in patients with testicular torsion, mumps orchitis, and trauma usually showed heterogeneous echogenicity. Atrophic testes were homogeneously hypoechoic in patients with cryptorchidism and inguinal hernia and were isoechoic to the normal testis in patients with varicocele. Klinefelter syndrome patients had small hyperechoic or hypoechoic nodules, but the echogenicity of the remnant portion of the testes was homogeneous. Ultrasonography is helpful for detecting small testes and for the differential diagnosis of the various possible causes of small testes.
Keywords: Color Doppler ultrasonography; Small testes; Testicular atrophy; Testis; Ultrasonography.