No sperm because of a blockage: production is usually fine.

Obstructive azoospermia is no sperm in the semen because the route out is blocked or missing, while the testes are making sperm.

Sperm travels from the testis through the epididymis and the vas deferens before joining the fluid. A blockage on both sides leaves fluid with no sperm. Azoospermia is never diagnosed on one sample: it needs two semen tests with the spun sample checked, because even a few sperm changes the diagnosis.

No: obstructive azoospermia does not affect testosterone, sex drive, erections or ejaculation.

Semen volume is usually normal, which is why it goes unnoticed until a test. It is not a sign of cancer. It is not caused by masturbation or anything he did. And it does not mean he cannot be a biological father.

Normal-sized testes with a normal FSH suggest a blockage; small, soft testes with a raised FSH suggest the testes are making little sperm.

Examination comes first. Whether both vas deferens can be felt can settle the diagnosis in the room. Blood tests follow (FSH, LH, testosterone). A urine test after ejaculation rules out retrograde ejaculation, which can look exactly like a blockage. Scans are added only for selected men.

If neither vas can be felt, the likely cause is congenital absence of the vas deferens, and both partners are offered a CFTR (cystic fibrosis gene) test.

More than half of men with this finding carry a CFTR gene change. If both partners carry one, a child could have cystic fibrosis. Genetic counselling, and a talk about testing embryos, then comes before treatment, not after.

There are two routes: microsurgery to reconnect the tubes, or collecting sperm directly from behind the blockage and using it with ICSI.

Reconstruction can allow natural conception but takes months to show a result and is not possible when the vas is missing [CONFIRM: surgeon Jananam works with]. Retrieval (PESA from the epididymis, or TESA from the testis) is a day procedure under local anaesthesia or short sedation, and works whatever the anatomy. Retrieved sperm is used with ICSI, and spare sperm is frozen to avoid a repeat procedure.

A blockage that is bypassed is not cured: retrieval gives sperm for treatment, and it does not restore natural fertility.

A repaired tube does not always stay open. Her age and egg reserve belong in the choice, because months spent waiting on a repair are not free. In some men the picture sits between blockage and low production, and we say so rather than force a label.