There is no obvious line of demarcation between normal testes and atrophied testes. The testes are located in the scrotum, one on each side, on average 4 to 5 cm long, 2.5 to 3.5 cm wide, and weighing about 10.5 to 14 g. The volume of both sides of the testes is approximately the same in normal adult men. The volume of the testes (including the scrotal skin) is often measured using an internationally used testicular volume measuring device. The range of testicular size in Chinese is 15 to 25 sizes. A clinical diagnosis of “testicular atrophy” is often made with a size smaller than 12. Testicular volume is an important diagnostic indicator in the clinical work of masculology (male infertility fertility regulation). Testicular volume in Chinese adult men Type Longitudinal diameter X Transverse diameter (cm) 15 4.29X2.58 20 4.55X2.93 25 5.01X3.01 The causes of small testicles can be broadly classified as congenital or acquired. Congenital belongs to testicular dysplasia. When suffering from infantile sexual organs, hypopituitarism, etc., both sides of the testes are often underdeveloped. If an abnormality occurs during embryonic development and causes incomplete testicular descent or cryptorchidism, the testicles on both sides are underdeveloped because the temperature in the abdominal cavity is higher than that in the scrotum. Acquired testicular atrophy is usually caused by trauma, testicular disorders and infections. Closed trauma to the testicle can cause testicular hemorrhage and infarction. Sharp objects such as nails and wires can also pierce the testicles. Trauma can also cause torsion of the spermatic cord and obstruct the blood supply, and endanger the survival of the testicle. Therefore, testicular injuries should be treated early. Certain diseases, such as varicocele, can sometimes cause testicular atrophy, and the veins in the male spermatic cord can become trapezius coiled and dilated due to some obstruction of reflux, called varicocele. In male infertility, varicocele accounts for about 15% to 20% of the cases. The testes of those with severe varicocele infertility generally have more atrophy. Testicular atrophy may be caused by depression of the spermatic veins, higher than normal scrotal temperature, testicular nutritional disorders, and toxins. Infection is also an important cause of testicular atrophy. Most commonly, mumps can cause viral orchitis. If it develops after puberty, mumps complicated by orchitis can cause a severe local inflammatory reaction. Excessive fluid may accumulate in its sphincter cavity, i.e., acute syringomyelia. Smallpox, chickenpox, measles, influenza, and other similar infections can occasionally cause secondary orchitis. To clinically determine if the testes are atrophied, in addition to measuring the volume size of the testes, one must also note how the texture is. On examination, a softer testicle texture indicates a more severely damaged testicular parenchyma. When it is difficult to determine if the testicles are atrophied, a semen examination can be very helpful. Testicular atrophy can occur on one side or bilaterally, if one testicle is congenitally missing, or has been surgically removed, or is destroyed by disease, and the opposite testicle has compensatory enlargement. The most accurate method to diagnose testicular atrophy is testicular biopsy and pathological examination. This test should be considered when diagnostic difficulties occur.