Azoospermia Explained: Obstructive vs Non-Obstructive and Surgical Sperm Retrieval

Azoospermia, the complete absence of sperm in the ejaculate, is found in a small but important proportion of men evaluated for infertility. Correct laboratory diagnosis and a structured clinical workup are essential, because the cause determines whether sperm can be retrieved and how.

Confirming azoospermia in the laboratory

A diagnosis of azoospermia should never rest on a single routine count. Following the WHO 6th edition laboratory manual:

• Examine at least two semen samples
• If no sperm are seen in the initial assessment, centrifuge the sample and examine the pellet carefully before reporting azoospermia
• Report whether any sperm were found in the centrifuged pellet. Finding even a few sperm (cryptozoospermia) changes management, because these sperm may be usable for ICSI
• Check semen volume and pH, and consider a post-ejaculatory urine sample when volume is low, to look for retrograde ejaculation

See our guide to semen analysis under the WHO 6th edition for the full method.

Obstructive vs non-obstructive azoospermia

Obstructive azoospermia (OA)

Sperm are produced normally but cannot reach the ejaculate because of a blockage. Causes include:

• Congenital bilateral absence of the vas deferens (CBAVD), often associated with CFTR gene variants
• Previous infection, including tuberculosis
• Vasectomy or inguinal surgery
• Ejaculatory duct obstruction

Typical findings: normal testicular volume, normal FSH and, with distal obstruction, low semen volume and low pH.

Non-obstructive azoospermia (NOA)

Sperm production in the testes is severely reduced or absent. Causes include:

• Genetic conditions such as Klinefelter syndrome (47,XXY) and Y-chromosome microdeletions (AZF regions)
• Undescended testes, previous chemotherapy or radiotherapy, or mumps orchitis
• Hormonal causes such as hypogonadotropic hypogonadism, which can often be treated medically

Typical findings: small testes and raised FSH, although these are not absolute.

Clinical workup

• History and examination, including testicular volume and palpation of the vas deferens
• Hormones: FSH, LH, testosterone and prolactin
• Genetic tests: karyotype and Y-chromosome microdeletion analysis in NOA; CFTR testing when the vas is absent, with partner testing and genetic counselling
• Scrotal and, when indicated, transrectal ultrasound

Our male infertility workup guide covers this in more detail.

Surgical sperm retrieval

When sperm cannot be obtained from the ejaculate, they may be retrieved surgically and used for ICSI:

• PESA (percutaneous epididymal sperm aspiration) and MESA (microsurgical epididymal sperm aspiration): used mainly in obstructive azoospermia
• TESA (testicular sperm aspiration): a needle aspiration of testicular tissue
• TESE (testicular sperm extraction): open biopsy of testicular tissue
• Micro-TESE (microdissection TESE): uses an operating microscope to identify tubules more likely to contain sperm; commonly preferred in non-obstructive azoospermia

In obstructive azoospermia, sperm can be retrieved in most men. In non-obstructive azoospermia, retrieval is possible in some men but not all, and couples should be counselled about this uncertainty, including options such as donor sperm, before surgery.

The andrology lab's role

The laboratory processes retrieved tissue by mechanical dispersion and sometimes enzymatic digestion, searches carefully for sperm, and cryopreserves any surplus so that the man may avoid repeat surgery. Our guide to sperm cryopreservation and semen banking explains the process. Donor sperm, if used, must come from an ART bank registered under the ART (Regulation) Act, 2021.

Frequently asked questions

How is azoospermia confirmed?

By examining at least two semen samples, including centrifugation and careful examination of the pellet, before reporting that no sperm are present.

Can men with azoospermia have biological children?

Many can. In obstructive azoospermia, sperm can usually be retrieved surgically for ICSI. In non-obstructive azoospermia, sperm may be found in some men, often using micro-TESE, but retrieval is not successful in every man.

Why is genetic testing recommended in azoospermia?

Conditions such as Klinefelter syndrome, Y-chromosome microdeletions and CFTR variants affect the chance of sperm retrieval and may be passed on to children, so testing and genetic counselling are important before treatment.

Train in andrology laboratory methods

ReproNest's Advanced Andrology & Semen Analysis Certification (WHO 6th Edition Protocols) covers semen examination, sperm function tests, sperm preparation and cryopreservation. Read about building a career in andrology, or contact our team.

This article is educational content for healthcare professionals and trainees. It is not medical advice and does not replace clinical judgement, current guidelines or the ART (Regulation) Act 2021 and Rules 2022.