Sperm is produced in the seminiferous tubules and is transferred to the epididymis. This is a tube coiled inside of the scrotum. This duct is actually about twenty feet long, but is coiled very tightly and runs behind the testes, forming a duct. This duct is a passage for sperm to travel down as they grow and mature before they are expelled. When this duct becomes blocked, it is referred to as an epididymal obstruction.
Epididymal obstructions prevent the sperm from ever making it to the ejaculate. Obstructions can occur on one side or both sides. One sided blockages normally cause a man to have a low sperm count. A two sided blockage can cause the sperm count to be as low as zero. This condition is referred to as azoospermia.
An epididymal obstruction can sometimes be felt in a simple physical exam. Blockages can cause the epididymis to become swollen and hard. Azoospermia can be caused by the sperm not being produced or not being delivered due to an epididymal obstruction. An infertility specialist will determine which is the cause if you are experiencing azoospermia. If any sperm are being produced, then they can be manually retrieved and can be used for conception through in-vitro fertilization or intracytoplasmic sperm insertion, so a zero sperm count does not always mean that you can not father a child.
Blockages of the epididymis can usually be surgically repaired. Success rates may depend on the cause of the blockage. Some blockages are naturally occurring, some can be caused by hernia or from the repair of a hydocele.
Your infertility specialist may need to take a tissue sample from the testis to determine if sperm production is happening. If it is, then a blockage may be diagnosed. After that, you may consider surgery to bypass the blockage. This surgery is called vasoepididymostomy. This bypass connects the vas deferens to the epididymis.
Many men choose sperm retrieval for use in in-vitro fertilization or intracytopolasmic sperm insertion over surgery. Sperm can be retrieved with a needle or incision into the testis. Another option is to retrieve the sperm directly from the epididymis through a Microscopic Epididymal Sperm Aspiration (MESA). This is a common choice because the sperm are more mature when taken from the epididymis. There is also more sperm to be retrieved from the epididymis than the testis. Sperm can be harvested and frozen for future in-vitro fertilization attempts.