Nonobstructive vs. Obstructive Azoospermia

What is Azoospermia?

Azoospermia is the absence of sperm in your semen.  Although this sounds very unpleasant to a man trying to father a child, most men with azoospermia are able to achieve biologic fatherhood.

There are two broad categories of azoospermia:

  • Obstructive azoospermia (OA)
  • Nonobstructive azoospermia (NOA)

What is Obstructive Azoospermia?

Obstructive azoospermia basically means there is a blockage somewhere in the reproductive tract.  Your testicles are normally producing sperm, but there is a blockage or obstruction somewhere in the reproductive tract. Depending on where the blockage is, men with obstructive azoospermia can have reduced volumes of semen when the ejaculate.

What causes Obstructive Azoospermia (OA)?

Common causes of obstructive azoospermia include:

  • Vasectomy – This is the most common cause of OA. This surgical procedure disrupts vas deferens (sperm duct) to stop the flow of sperm. A vasectomy reversal or sperm retrieval are viable options to treat obstructive azoospermia after vasectomy.
  • Radical prostatectomy – Similar to a vasectomy, this surgical procedure interrupts the flow of sperm. Sperm retrieval procedures are viable options to treat obstructive azoospermia after radical prostatectomy.
  • Severe infections of the male reproductive tract – Infections of the testicles, prostate, or epididymitis can cause scarring and blockage in the small tubules of the epididymis or ejaculatory duct.
  • Congenital Conditions – In some cases, men are born missing a portion of the vas deferens, blocking the flow of sperm out of the testicles. In other cases, men are born with a cyst in the prostate that blocks the path of sperm out of the ejaculatory ducts.

What is Nonobstructive azoospermia (NOA)

Nonobstructive azoospermia means that the reproductive tract is open, but there is a sperm production problem where either are no sperm being produced or there is a very low level of sperm production that need to be surgically extracted to use for in-vitro fertilization.  Nonobstructive azoospermia doesn’t mean there is no chance a man can produce sperm.  There are many reasons, many of these reversible, why a man may have nonobstructive azoospermia.

What causes Nonobstructive Azoospermia?

Some common causes of NOA are listed below.

  • Varicocele – The most common cause of male infertility due to varicose veins around the testicles. While most varicoceles only cause a minor decrease in total sperm counts, in some cases, the varicocele can result in azoospermia. This is easily corrected through a surgical procedure called a varicocelectomy.
  • Steroid/Testosterone-induced – one of the most common causes of NOA. Men with a history of testosterone replacement therapy use will have poor or no sperm production. This can often be reversed.
  • Chronic Narcotics – Men on chronic narcotics often have impaired testosterone and sperm production that can be reversed. 
  • Sertoli-Cell Only Syndrome (SCO) – In this scenario, the germ cells that divide and become sperm are absent from the testicular architecture. Approximately, 15-20% of men with SCO will have some low level of sperm production occurring in the testicles. Since abnormal sperm production in the testicle is not homogeneous, one region of the testicle might have an SCO pattern, while another area might have some germ cells and some mature sperm. Using microsurgical sperm extraction techniques, we are able to examine the seminiferous tubules and identify the regions that could potentially have germ cell activity.
  • Maturation arrest – Problems in sperm development cause the testicle to be comprised of only precursor sperm. There is roughly a 50% chance of finding mature usable sperm in the setting of maturation arrest.
  • Chromosomal/Genetic Abnormalities – Chromosomal abnormalities include aneuploidy, where there is a presence of an abnormal number of chromosome or translocations, where a part of one chromosome break off and attaches to another chromosome. The most common chromosomal problem causing azoospermia in men is, Klinefelter Syndrome, where there is an extra X chromosome.

The Y-chromosome is what provides men with their “male characteristics” and is intimately involved in sperm production. A common genetic cause of azoospermia is a deletion of the genes on the Y-chromosome. Azoospermia can happen when one or more of the genes on this chromosome are deleted.

Although genetic causes of azoospermia are not reversible, most men still produce small amounts of sperm that can be used to achieve biologic fatherhood.

  • History of Chemotherapy and Radiation :Chemotherapy and radiation therapy for previous cancer therapy can cause temporary azoospermia. However, sperm production should return to normal within two years following therapy, depending on the type and length of treatment received.

Have a question or want to schedule an appointment?

Board-certified, fellowship-trained urologists staff Tower Men’s Health. We will pair you with one of our many experienced physicians to help address any concerns you may have and help you on your journey towards improved quality of life. Feel free to reach out to the physicians at Tower Men’s Health at 310-854-9898.