10.1 Introduction

Sperm retrieval techniques have been developed to obtain spermatozoa from the epididymis and testicles of azoospermic men. Following sperm acquisition, intracytoplasmic sperm injection (ICSI) may be used for couples interested in biological offspring when the male partner has azoospermia, or the sperm may be cryopreserved for future sperm injections. The surgical method of choice varies based on whether the azoospermia is secondary to obstructive or nonobstructive etiologies, both of which may be a result of congenital or acquired conditions. For patients with obstructive azoospermia, microsurgical ductal recanalization is highly successful; however, certain congenital anomalies or post-infectious etiologies may not offer a successful outcome and therefore sperm retrieval will be necessary. In this situation, successful spermatozoa retrieval can still be achieved from the epididymis or testicles, with the choice of sperm retrieval method based on the surgeon’s preference and experience, and the patient’s underlying etiology [1,2]. Patient preferences and female infertility can also play a role in recommending sperm retrieval in cases of obstructive azoospermia.

In men with obstructive azoospermia, percutaneous epididymal sperm aspiration (PESA) and microsurgical epididymal sperm aspiration (MESA) are two procedures that have been successfully utilized. Other notable techniques are percutaneous testicular sperm aspiration (TESA) and testicular sperm extraction (TESE) for failed epididymal retrieval in obstructive cases. There are clear advantages and disadvantages between the PESA and MESA techniques for obstructive cases. The PESA technique requires local anesthesia only, can generally be performed at shorter notice, requires no special equipment, and is 2–3 times cheaper than other methods such as MESA. However, a lower quantity of sperm is normally retrieved or there is a higher failure rate, with the need to convert to TESE. The MESA technique requires an operating microscope, general anesthesia, and microsurgical training, but leads to higher sperm retrieval rates [3]. A study of 100 cases between these methods showed that PESA was successful in extraction 61 percent of the time. Upon PESA failure, MESA was subsequently performed, with a sperm retrieval rate of over 90 percent [4]. The technique selected is dependent on many factors, including cost, technology available, and overall knowledge of the procedure.

Nonobstructive azoospermia (NOA), the most common cause of azoospermia, is a result of spermatogenic failure that can be due to Sertoli-cell-only syndrome (SCOS), maturation arrest, or hypospermatogenesis. Patients with NOA were once considered to be infertile, with few treatment options secondary to the absence of sperm in the ejaculate. However, over the last two decades, a number of sperm retrieval techniques have revolutionized the treatment for NOA men. Primary therapies for patients with NOA are TESA and TESE. Again, each of these techniques has advantages and disadvantages related to ease, cost, repeatability, patient discomfort, risk of hematoma, and number of sperm retrieved for cryopreservation. Overall, success retrieval rates for patients with NOA, implying focal areas of sperm production within the testes, range from 30 to 60 percent; notably, sperm retrieval is the highest for micro-TESE, discussed subsequently, and the lowest for TESA [5,6].

10.2 Procedural Technique Enhancements

In the past decade, there has been a strong focus on newer techniques to achieve a more adequate number of, and the highest quality, sperm possible, while also preserving testicular function and reducing the number of repeated retrieval attempts. The microdissection technique was originally described in 1999 following observations noted during TESE procedures. To avoid damage to the testicular blood supply, the operating microscope was used to identify subtunical vessels prior to surgical incision at the time of biopsy. Microdissection has allowed for better visualization of seminiferous tubules to locate ones that are more promising. This technique, known as microdissection testicular sperm extraction (micro-TESE), is now considered the gold standard method of sperm retrieval utilized in patients suffering from NOA. A meta-analysis comprising 15 individual studies and 1890 patients compared the outcome differences between conventional TESE (cTESE) and micro-TESE. It was observed that spermatozoa retrieval for cTESE was successful in 35 percent of patients, while for micro-TESE, the success rate improved to 52 percent. In fact, microdissection has enhanced sperm retrieval success by making it 1.5 times more likely [7,8]. Moreover, targeting the larger tubules during microdissection at 15–20× power also improves sperm retrieval yield and limits the amount of tissue that needs to be removed. If, however, microdissection fails, other techniques have shown some promise. One of these techniques is testicular mapping with fine-needle aspiration (FNA). These maps are performed on azoospermic men through simple and compound mapping techniques. In a series of 159 mapped cases, if at least one site was discovered containing mature sperm, this FNA map-guided TESE proved to be highly efficacious and rescued over 80 percent of those with prior failed micro-TESE attempts, resulting in successful retrieval [9].

10.3 Medical Adjuvant Therapy

Aside from FNA mapping, there are also various medical adjuvant therapies that have been shown to increase the success rates of micro-TESE by aiding spermatogenesis. Shiraishi et al. studied 48 men with NOA who had unsuccessful sperm retrieval results on first micro-TESE. Of these, 20 were not treated with any hormonal therapy, while 28 received daily injections for four months of human chorionic gonadotropin (hCG), and recombinant follicle-stimulating hormone (FSH) if endogenous gonadotropin levels decreased during hCG stimulation. A second micro-TESE procedure 4–5 months later was successful for more than 20 percent of the treated group, while no sperm was extracted from the control set [10]. Additionally, Hussein et al. have made a similar case for treatment with clomiphene citrate, a selective estrogen receptor modulator (SERM). A comparison of men with NOA was set up consisting of 116 patients who received no medical treatment and 442 who were administered clomiphene citrate in titrated doses. Micro-TESE was then subsequently performed in both groups. Overall, successful sperm retrieval was significantly higher for the clomiphene treated group (57 percent) than for the control group (33 percent) [11]. These findings indicate that surgeons can consider medical adjuvant therapy as a way to increase successful sperm extraction.

10.4 Innovations in Imaging

Despite all of these procedural improvements, it has remained a challenge to distinguish between seminiferous tubules with normal versus abnormal spermatogenesis. Recently, advances in high-level imaging of the seminiferous tubules has proven to be very promising; however, many of these are either in animal studies or only in preliminary testing stages and further work is required to optimize these techniques for human fertility issues. One technique that can possibly identify the presence of sperm within the tubules, without the need for tissue extraction, is multiphoton microscopy (MPM). In a mouse model, MPM has been shown to distinguish underlying microstructures of different seminiferous tubules. It works by using a low-energy infrared pulse laser to excite molecules, causing autofluorescence. However, MPM laser-guided techniques still need to be evaluated for long-term safety as lasers can potentially induce genetic abnormalities in gametes associated with ICSI [12]. A second technique for better visualization of spermatogenesis in tubules is full-field optical coherence tomography (FFOCT). This is a technique that uses white-light inference microscopy to produce high-resolution images. In a mouse model, FFOCT has been demonstrated to successfully image the tubules and determine the status of spermatogenesis [13]. While this technique holds promise for reducing the number of biopsies performed and decreasing operative time for the micro-TESE procedure, one limitation is its limited depth of imaging. Raman spectroscopy, a tool of laser-based optics, has successfully distinguished between those with Sertoli-cell-only histology and tubules with spermatogenesis. Finally, antibody labeling of sperm in the seminiferous tubules may reduce operative time and more readily identify sperm-filled tubules; however, the practicality of performing this in humans has not been proven [14]. Thus, in recent years, many innovative techniques such as microdissection and FNA mapping have come to clinical fruition. Additionally, enhanced imaging modalities, while in their infancy, are showing promise and likely will have a significant impact in the future. Together, these have significantly improved sperm retrieval success for those suffering from NOA. Large-scale collaborative studies will help identify the most promising imaging and retrieval technique combinations in this field.