ICSI and Surgical Sperm Retrieval
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Direct answer
Intracytoplasmic sperm injection, or ICSI, is IVF in which a single sperm is injected directly into a mature oocyte to achieve fertilisation. It is indicated for severe male factor, previous fertilisation failure and surgically retrieved sperm, and surgical retrieval is required when no sperm are present in the ejaculate.
What you must remember
- ICSI indications: Severe oligozoospermia, previous fertilisation failure with standard IVF, poor motility or morphology, and surgically retrieved or frozen sperm.
- Count threshold: Severe oligozoospermia is usually a count below 5 million per mL.
- TESA: Testicular sperm aspiration with a fine needle under local anaesthesia, used for obstructive azoospermia and some non-obstructive cases.
- Micro-TESE: Microdissection testicular sperm extraction under an operating microscope, preferred for non-obstructive azoospermia because it targets the most dilated tubules.
- PESA: Percutaneous epididymal sperm aspiration, used for obstructive azoospermia such as congenital bilateral absence of the vas deferens.
- Genetic counselling: Karyotype, Y microdeletion analysis and CFTR testing come before ICSI with surgically retrieved sperm, because the genetic cause can be passed to offspring.
A stepwise approach to surgical retrieval
Vignettes present an azoospermic man with a hormone profile and testicular findings, and the choice of retrieval follows the steps below.
- Classify the azoospermia: Hormones, testicular volume and scrotal ultrasound separate obstructive from non-obstructive disease.
- Choose the retrieval: Use PESA or TESA for obstructive disease, and micro-TESE for non-obstructive disease, guided by FSH and testis size.
- Test for a genetic cause: Send karyotype and Y microdeletion analysis for azoospermia, and CFTR testing in congenital bilateral absence of the vas deferens, before retrieval.
- Plan the ICSI cycle: Retrieved sperm, used fresh or frozen, are injected into mature (metaphase II) oocytes collected during the IVF cycle.
- Counsel the couple: Explain that sperm may be absent at surgery, that retrieval success varies, and that any genetic defect found can be transmitted to the child.
The genetic work-up also matters for the child, because some defects are passed to sons and daughters through the father.
Where the exam tries to catch you
Retrieval questions reward the option that matches the type of azoospermia and that protects against a hidden genetic cause.
- Trap: Assuming TESA is always enough for non-obstructive azoospermia. Correct: Micro-TESE gives better sperm retrieval in non-obstructive disease because it targets the most dilated tubules.
- Trap: Doing ICSI without a genetic work-up in severe male factor. Correct: Karyotype and Y microdeletion testing should precede ICSI, since a genetic defect can be passed to offspring (a Y microdeletion to sons, a CFTR mutation to either sex).
- Trap: Assuming an AZFa or AZFb deletion still allows retrieval. Correct: Those deletions usually mean no sperm, so retrieval is unlikely to succeed and donor options are discussed.
Frequently asked questions
When is ICSI preferred over conventional IVF?
ICSI is preferred over conventional IVF for severe oligozoospermia, poor sperm motility or morphology, previous fertilisation failure and surgically retrieved sperm. It places a single sperm inside the oocyte, so fertilisation does not depend on the sperm penetrating the zona pellucida unaided.
What is the difference between TESA and micro-TESE?
TESA uses a fine needle to aspirate sperm from the testis under local anaesthesia, while micro-TESE uses an operating microscope to find and extract sperm from the most dilated tubules. Micro-TESE is preferred for non-obstructive azoospermia because it gives higher retrieval rates in selected men.
Which sperm retrieval is used in congenital bilateral absence of the vas deferens?
In congenital bilateral absence of the vas deferens, percutaneous epididymal sperm aspiration is commonly used, with sperm obtained from the epididymis. CFTR gene testing is essential in these men because the condition is linked to CFTR mutations.
Why is genetic counselling necessary before ICSI with surgically retrieved sperm?
Genetic counselling is necessary because azoospermia and severe oligozoospermia can have chromosomal or Y microdeletion causes, and these can be inherited by offspring. Karyotype, Y microdeletion analysis and CFTR testing identify these risks before ICSI is planned.