Obstructive Azoospermia (OA)
Normal sperm production, but a blockage in the way — usually very treatable
In obstructive azoospermia (OA), the testicles produce sperm normally, but a blockage somewhere along the pathway prevents sperm from reaching the semen. Because production is healthy, the outlook is often very good.
What causes obstructive azoospermia?
- Previous vasectomy — a deliberate blockage that can be reversed or bypassed.
- CBAVD — congenital absence of the vas deferens, the tubes that carry sperm, strongly linked to the cystic fibrosis gene.
- Infection or previous surgery — scarring of the epididymis or vas.
- Ejaculatory duct obstruction (EDO) — a blockage near where the tubes drain.
How OA is diagnosed
Two simple features of the semen often point the way, alongside examination and blood tests:
- Low-volume, acidic semen suggests a blockage low down (EDO) or absent vas (CBAVD).
- Normal-volume semen with normal hormones and normal-sized testes suggests a blockage of the vas or epididymis — for example after a vasectomy.
- Examination — Mr Wiseman checks whether the vas can be felt and whether the epididymis feels full, which strongly indicates a blockage.
- FSH is usually normal in OA, and the testes are a normal size.
Treatment options
Surgical reconstruction
Where the blockage can be bypassed — most commonly after a vasectomy — a microsurgical reconstruction can restore the natural flow of sperm, offering the chance of conceiving naturally. See our dedicated page on vasectomy reversal.
Surgical sperm retrieval
Sperm can also be collected directly using PESA (aspiration from the epididymis) or TESE (from the testicular tissue), then used with IVF/ICSI. Because production is normal in OA, these procedures are usually very successful. For ejaculatory duct obstruction, a minor operation (TURED) can sometimes relieve the blockage. Read more about surgical sperm retrieval.
Choosing the right path
The best option depends on the cause of the blockage, your wishes, and your partner's fertility. Mr Wiseman will talk you through reconstruction versus sperm retrieval clearly, and coordinate any IVF/ICSI with the teams at Bourn Hall Clinic and Cambridge IVF.
Frequently asked questions
What is the difference between obstructive and non-obstructive azoospermia?
In obstructive azoospermia the testicles make sperm normally, but a blockage stops the sperm reaching the semen. In non-obstructive azoospermia the problem is reduced production. The distinction matters because it changes treatment, and it can usually be made from your semen results, hormones and examination.
I have had a vasectomy — what are my options now?
You have two excellent options: a microsurgical vasectomy reversal to restore the natural flow of sperm, or surgical sperm retrieval (such as PESA or TESE) combined with IVF/ICSI. Mr Wiseman will help you choose based on your circumstances and your partner’s fertility.
What is CBAVD and why does the cystic fibrosis gene matter?
CBAVD (congenital bilateral absence of the vas deferens) means the tubes that carry sperm are missing from birth. It is strongly linked to the cystic fibrosis gene. Because of this, both partners are offered genetic testing and counselling before treatment, so the chance of a child being affected can be understood and planned for.
Is the chance of success good with obstructive azoospermia?
Generally yes. Because sperm production is normal, sperm can almost always be obtained — either by reconstructing the blockage or by retrieving sperm directly — for use in natural conception or IVF/ICSI.
Discuss treatment for obstructive azoospermia
Book a private consultation with Mr Oliver Wiseman, or arrange an NHS referral through your GP. Face-to-face, telephone and video appointments are available.