The path of the sperm cells can be obstructed in several places:
- In the testicles, where sperm cells are produced
- In the epididymis, the tube that carries sperm from the testicle to the vas deferens
- In the vas deferens, the tube that transports sperm to the prostate and posterior urethra
The most common causes of obstruction are infections (for example, gonorrhoea, chlamydia, prostatitis, tuberculosis), birth defects (congenital disorders), or trauma to the genitalia.
Treatment depends on the amount of obstruction. Semen can be collected by biopsy from the testicle or the epididymis. Surgery on the vas deferens can reestablish the pathway.