What are the reasons for no semen and no sperm?

Patient's question:

Ejaculation without semen, let alone sperm. Erection is also a bit obstructed

Doctor's answer:

In adult male semen, the absence of sperm can be attributed to two primary reasons:
1. Obstruction in the production or development of sperm within the testes, which can be caused by congenital testicular dysgenesis or secondary testicular diseases or injuries. In such cases, apart from the absence of sperm in the semen, other abnormalities may also be present, such as testicular atrophy (significant shrinkage) or soft texture. The most accurate diagnostic method is a testicular biopsy, which can accurately determine the number of spermatogonia in the testes. If both testicles are significantly atrophied and soft, or if the biopsy reveals a very low number of spermatogonia, it will be extremely difficult to restore fertility.
2. Obstruction in the transport of sperm from the testes to the seminal vesicles, also known as vas deferens obstruction. This occurs when a mechanical blockage occurs at a certain point in the reproductive tract, preventing the sperm produced by the testes from passing sequentially through the testicular meshwork, epididymis, vas deferens, ejaculatory duct, and urethra for expulsion. Further examination is required to identify the cause.