Surgical sperm retrieval and its use in infertility treatment

For most of human history, fertilisation of a single egg produced by the female partner involved a swimming race between millions of sperm. The single winning sperm was the one that entered the egg first. The modern infertility treatments intracytoplasmic sperm injection (ICSI) and in vitro fertilisation (IVF) now make it possible to extract a single sperm and use it to directly fertilise an egg. The latest surgical sperm retrieval techniques combined with ICSI and IVF also mean that infertility can be overcome even in men who produce hardly any sperm.

A low sperm count is a common cause of male infertility but if a man produces even the tiniest number of sperm in his semen, these can be collected fairly easily. Men who ejaculate no sperm, because of blocked tubes in their testes, or because of a genetic condition that prevents their sperm being released, require some form of surgical sperm retrieval to enable intracytoplasmic sperm injection to take place.

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Methods of surgical sperm retrieval

The main methods of surgical sperm retrieval available include:

• PESA: percutaneous epididymal sperm aspiration.
• MESA: microsurgical epididymal sperm aspiration.
• TESA: testicular sperm aspiration. This includes testicular fine needle aspiration (TFNA).
• TESE: testicular sperm extraction.
• Microdissection TESE.
• Perc biopsy: percutaneous biopsy of the testis.

Which method is used depends on the nature of the problem in the male partner, which needs to be explored carefully first.

Tests required before surgical sperm retrieval

A man that produces no sperm in his semen is said to have azoospermia. This may be because of a blockage in one of the tubes that carry sperm from the areas of the testes where they are produced, out to the penis during ejaculation. Obstructive azoospermia can be caused by testicular cancer, as the tumour presses on the vas deferens. This type of cancer is common in young men and can be treated successfully. It can, however, lead to infertility, so surgical sperm retrieval may be performed to store some sperm before treatment begins.

Other conditions cause non-obstructive azoospermia, including having an abnormal cystic fibrosis gene. Men with this condition may not show all the symptoms, but they often have no vas deferens. Surgical sperm retrieval is possible but there is a 50:50 chance that the embryos produced by subsequent ICSI and IVF will have the same genetic abnormality. Options then include using a sperm donor and intrauterine insemination (IUI) or IVF, or having pre-implantation genetic diagnosis (PGD) performed on the embryos to select ones that carry the normal gene.

If the problem that underlies poor sperm production is physical rather than genetic, or if a couple wants to have children after the male partner has had a vasectomy that cannot be reversed, surgical sperm retrieval can go ahead.

Surgical sperm retrieval techniques used when obstruction is the problem

When the release of sperm is prevented by a blockage in the vas deferens, or by a vasectomy, several techniques can be used to retrieve the large numbers of sperm that remain inside the testes. The first three involve aspirating sperm using needles or tubes placed through the skin of the testis and are carried out under local anaesthetic. The fourth requires open surgical sperm retrieval and is usually carried out under general anaesthetic.

• TESA: testicular sperm aspiration. This involves placing a needle attached to a syringe through the skin of the scrotum and simply sucking out the fluid inside the testicle.
• PESA: percutaneous epididymal sperm aspiration. This involves the same needle and syringe technique but the needle is placed directly into the epididymis.
• Perc biopsy: percutaneous biopsy of the testis. This is similar to TESA, but a larger needle is used. This is a 14 gauge needle usually used to biopsy testicular tissue and it usually extracts a larger number of sperm.
• MESA: microsurgical epididymal sperm aspiration. An open surgical sperm retrieval procedure that uses an operating microscopy to locate the tubules of the epididymis precisely, so that large numbers of sperm can be extracted.

Some small studies have been done to compare success rates after the different types of surgical sperm retrieval. These concluded that MESA gives the highest number of sperm, with a hundred times more sperm being recovered compared to TESA and perc biopsy. MESA also produced sperm that were better swimmers and therefore more useful for infertility treatments, including IVF and ICSI.

Surgical sperm retrieval techniques when there is no obstruction

Men who have no sperm in their semen, despite having clear tubes in their testicles, usually have a problem with the process of sperm production. It is unlikely that sperm are present in large numbers, so the surgical sperm retrieval techniques required are more invasive.

• TESE: testicular sperm extraction. This involves opening up the scrotum and taking a large volume of testicular tissue, perhaps from several regions of the testicle. Sperm are then retrieved using a microscope to identify individual sperm.
• Microdissection TESE. A similar technique but a microdissecting microscope is used to pinpoint the tissue to be removed. This aims to cause less damage to the structure inside the testicle, and to therefore have fewer after effects such as blood supply problems caused by tiny blood vessels being cut. It also appears to increase the number of sperm that can be retrieved.

Success rates after surgical sperm retrieval

Evidence is still accumulating because all of these infertility treatments are relatively new, but one of the most successful combinations appears to be MESA followed by ICSI, which has reported fertilisation and pregnancy rates between 45 % and 52 %.