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How can a blockage in the genital tract cause azoospermia?

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Diagram showing the female reproductive system with labeled ovaries, fallopian tubes, uterus, and vagina, alongside hormone pathways and the process from ovulation to fertilization and early embryo development. — infertility Major structures and hormones involved in the initiation of pregnancy. Also seen, at right, is the development of an egg cell (ovum) from follicle to embryo.

Azoospermia is defined as the complete absence of spermatozoa in the ejaculate. While this condition can result from testicular dysfunction, it is also frequently caused by a physical obstruction within the male genital tract.1

The male genital tract—comprising the epididymis, ductus deferens, and ejaculatory ducts—serves as the essential pathway for transporting sperm from the testes to the urethra. When these pathways are blocked by factors such as adhesions or obstructive growths like cysts, sperm are physically prevented from moving through the ducts and exiting the body during ejaculation.23

Because the sperm cannot reach the ejaculate despite being produced in the testes, the resulting semen sample will show no sperm count. In such cases, medical professionals may use procedures like microsurgical epididymal sperm aspiration (MESA) to retrieve sperm directly from the epididymis for use in assisted reproductive technologies.13