Keywords

15.1 Introduction

Azoospermia is defined as the absence of sperm in the ejaculate. This diagnosis is confirmed by centrifugation of a semen specimen for 15 min and at least two semen samples obtained more than two weeks apart should be examined [1].

Azoospermia should be distinguished from cryptozoospermia, when rare nemasperms (<500,000) are present after centrifugation of the seminal fluid, and aspermia, defined as the complete absence of seminal fluid emission during orgasm.

15.2 Classification

Although many causes of azoospermia have been described, all etiologies can be categorized in pre-testicular, testicular, and post-testicular conditions:

  • Pre-testicular causes include hypothalamic-pituitary-gonadal axis abnormalities.

  • Testicular causes include intrinsic disorders of spermatogenesis inside the testes.

  • Post-testicular etiologies include obstruction at any location of the male seminal tract and ejaculatory disfunctions.

In most cases, the assessment of both clinical and laboratory findings, including semen volume, testicular volume, palpable vas deferens and serum FSH, LH, and inhibin B levels, will facilitate the differentiation between the three categories.

figure a

However, azoospermia is more commonly classified into two large groups:

  • Nonobstructive azoospermia (NOA) or secretory azoospermia due to a sperm production impairment (pre-testicular and testicular etiologies).

  • Obstructive azoospermia (OA) due to an obstruction of the passage of sperm along the seminal tract, leading to a complete absence of sperm in the ejaculate (post-testicular etiologies).

15.3 Epidemiology

The prevalence of azoospermia is approximately 1% among the general male population and ranges between 10% and 15% among infertile men [2]. The prevalence of OA and NOA is variable and depends on geographic areas and authors. However, NOA represents the main cause of azoospermia (60–75%). When considering fertility prognosis, OA showed more favorable outcomes.

15.4 Etiology

15.4.1 Pre-Testicular Etiology

15.4.1.1 Hypogonadotropic Hypogonadism (HH)

It is a very rare cause of NOA (<1%). The condition is characterized by decreased secretion of gonadotropins due to dysfunction of the hypothalamus or the pituitary gland.

HH recognizes both congenital and acquired causes. Congenital HH can be idiopathic (1/3 of the cases) or due to genetic syndromes (Kallmann syndrome, Prader-Willi syndrome). Acquired HH may be caused by pituitary lesions (tumor, granuloma, abscess) or injuries (irradiation, trauma, surgery), illicit drugs intake (anabolic steroids, opiates), alcohol abuse, hyperprolactinemia, and iron overload.

This condition is treatable with medical therapy that consists of gonadotropins (hCG, FSH), androgens, or GnRH administration. Therapeutic management depends on patient’s desire for future fertility. Androgen replacement alone (testosterone) is indicated for men who already have children or have no desire for children. Conversely, in men willing to reach fatherhood, treatment with human chorionic gonadotropin (hCG) alone or in combination with follicle-stimulating hormone (FSH) is mandatory to stimulate spermatogenesis.

15.4.2 Testicular Etiology

In almost all cases of NOA, the defect is at gonadal level. Intrinsic disorders of spermatogenesis are derived from genetic mutations, gonadotoxic effects from drugs, undescended testes, varicocele-induced testicular damage, testicular torsion, orchitis, and idiopathic causes. Despite definition of the exact etiology being desirable, subsequent conventional medical or surgical treatments are ineffective and sperm retrieval represents the only option.

15.4.2.1 Genetic Mutations

Chromosome alterations represent the most frequent genetic cause of azoospermia (15%) [3]. Several conditions have been identified:

Klinefelter syndrome is the most common numerical chromosome anomaly observed in infertile men occurring in 1:500 males [4]. It is characterized by X chromosome polysomy (47, XXY), even if a mosaicism has been also described (10% of cases). Affected men show small and hard testicles, azoospermia, and high levels of gonadotropins with low testosterone levels; the classical phenotype is characterized by tall eunuchoid body proportions.

47, XYY syndrome is caused by paternal nondisjunction during meiosis and occurs in 1:1000 men [5]. Patients present tall stature, azoospermia with normal serum testosterone level.

Y-chromosome microdeletion is caused by mutations of the gene localized in the AZF region (Yq). Three different forms have been identified due to mutation in AZFa, AZFb, and AZFc locus [6]; complete deletion of the AZFa and AZFb loci is always associated with the absence of spermatogenesis, with subsequent worse fertility prognosis [7].

15.4.2.2 Gonadotoxins

Medications (chemotherapy agents, irradiation, androgens, or antiandrogens) or environmental toxins (pesticides, solvents) can directly damage germ cells in the testis or cause disfunction of the Sertoli-cells [8]: in any case spermatogenesis is compromised. Many patients recover a normal sperm production months or years afterwards; however, in some cases, azoospermia is permanent.

15.4.2.3 Undescended Testis

Also defined cryptorchidism, it is a condition characterized by undescended testes/testis into the scrotum during embryonic development. Usually, the testicle remains in the inguinal canal (70%) or in the pre-scrotal region (20%); in these cases, germ cells count is compromised in 20–40% of patients. Conversely, if intra-abdominal retention occurs (8%), spermatogenetic dysfunction is recorded in 90% of cases. The probability of infertility is correlated with bilaterality and degree of retention.

15.4.2.4 Varicocele

The role of varicocele in determining azoospermia is still debated. In most cases, the two conditions are concomitant and not directly correlated. However, some authors have reported a beneficial effect of varicocele treatment in azoospermic patients, with the appearance of sperm in the ejaculate after correction. In particular, this improvement seems to be more likely when a histological diagnosis of hypospermatogenesis is present [9].

Current practice in azoospermic patients with clinically significant varicocele and no other clear causes of azoospermia is to schedule a bilateral TESE for sperm search, freezing, and histological evaluation, with simultaneous or delayed varicocele correction in selected cases [10].

15.4.2.5 Idiopathic Cause

Unfortunately, in almost 50% of NOA, it is not possible to determine the etiology of azoospermia. It is likely that in many of these conditions, an unknown genetical or congenital defect or a previous exposition to toxins is present.

15.4.3 Post-testicular Etiology

Obstruction of sperm transit and ejaculatory dysfunction represent post-testicular causes of azoospermia.

15.4.3.1 Obstruction of the Seminal Pathway

Obstructive conditions may affect:

  • Proximal seminal ducts.

    • Efferent ductules (testis).

    • Epididymis.

    • Vas deferens.

  • Distal seminal ducts.

    • Deferential ampullas.

    • Ejaculatory ducts.

15.4.3.1.1 Testicular Obstruction

Total absence of spermatozoa in the epididymis with preserved spermatogenesis is an extremely rare condition in the isolated form, and it is usually due to congenital malformation. Most commonly, it is associated with epididymal obstruction because of inflammation or infection.

15.4.3.1.2 Epididymal Obstruction

This condition is frequently diagnosed in patients with azoospermia (30–67%). Congenital obstruction could be secondary to bilateral agenesis of vas deferens (frequently associated with cystic fibrosis gene mutation) or Young’s syndrome. Acquired forms are mostly due to sexually transmitted infections (N. gonorrhoeae, Chlamydia) or iatrogenic (blow-out of the epididymal tubules in vasectomized patients, fibrosis after epididymal aspiration, hydrocele repair, or orchiopexy).

15.4.3.1.3 Vas Deferens Absence

Congenital bilateral absence of the vas deferens (CBAVD) is found in 1% of infertile men and in up to 6% of those with obstructive azoospermia [11]. There are two possible mechanisms responsible for this condition:

  • Mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. More than 800 different mutations have been described, but deletion in exon 10 (delta F508) is the most common mutation found in Caucasian population [12]. CFTR gene mutations have been detected in 80% of patients with congenital bilateral absence of the vas deferens and in 43% of men with unilateral absence [13].

  • Abnormalities in the differentiation of the mesonephric duct [14]. Any insult to the Wolffian duct before week seven of gestation may impair urinary and reproductive tract formation including partial epididymal aplasia, seminal vesicle aplasia, or hypospadias, which may lead to a low ejaculate volume. Secondary findings include ipsilateral renal agenesis and imaging confirmation is imperative in patients with unilateral or bilateral absence of the vas deferens, without CFTR gene mutations.

The clinical features of CBAVD include normal testicular volume with normal spermatogenesis and normal levels of FSH. The caput epididymis is always present, but corpus and cauda are found only occasionally. Seminal vesicles are often absent or atrophic, but may also be enlarged or cystic. Spermatozoa can be easily retrieved from the testis or the caput epididymis.

15.4.3.1.4 Vas Deferens Obstruction

Vasal obstruction etiologies include vasectomy, inguinal or scrotal surgery such as hernioplasty or hydrocelectomy, infection, or trauma. Inadvertent injury of vas deferens during surgical hernia repair is a common cause of the obstruction. Entrapment for fibrosis induced by contact with the mesh can be also possible. However, the most common cause of obstruction is vasectomy performed for selective sterilization [15]. The diagnosis is suspected when examination reveals normal testicular volume and epididymis full and firm.

15.4.3.1.5 Ejaculatory Duct Obstruction

Ejaculatory duct obstruction (EDO) is an uncommon cause of male infertility (1–5%) [16] and represents almost 10% of the obstructive forms of OA. It is characterized by the obstruction of one or both ejaculatory ducts and may be congenital or acquired [17].

Congenital causes of EDO include congenital atresia or stenosis of ED and prostatic cysts (utricular, Mullerian duct, and wolffian duct cysts). Acquired causes include iatrogenic trauma secondary to prolonged catheterization, pelvic or bladder outlet surgeries or pelvic trauma, infectious etiologies, stones, and prostatic abscesses which all may lead to calculi, inflammation, and scarring [17].

Bilateral complete EDO is characterized by low volume (<1.5 mL), low pH, and azoospermia without fructose in the ejaculate in the setting of normal hormonal values. In cases of partial obstruction, the patient may have oligoasthenospermia (OAT) with low-normal volume and low-normal pH. In addition to infertility, other symptoms may include pelvic or scrotal pain exacerbated by ejaculation and rarely hematospermia. Seminal vesicles study usually show dilation.

In absence of anatomic obstruction, there may be dysfunctional voiding of the ejaculatory apparatus without a physical obstruction [18].

15.4.3.1.6 Ejaculatory Dysfunctions

Although these represent a relatively unusual cause of male infertility, disorders of ejaculation include a variety of conditions with individualized treatment. Ejaculatory dysfunction should be suspected in any patient with low volume or absent ejaculate. Retrograde ejaculation can be defined as the abnormal backward flow of semen into the bladder with ejaculation; the etiology may be iatrogenic postsurgical, anatomic, neurogenic, pharmacologic, or idiopathic. The diagnosis is made by finding sperm in the post-ejaculate urinalysis.

15.5 Diagnosis

Accurate andrological evaluation is crucial to understanding the etiology of azoospermia.

15.5.1 Medical History

The first step for azoospermia assessment includes a detailed personal history: childhood illness (cryptorchidism, orchitis, testicular torsion), previous testicular trauma or surgery, history of irradiation, or medications.

15.5.2 Physical Examination

General examination can reveal typical phenotypes (Klinefelter syndrome, Kallmann syndrome) and allows sexual development evaluation. Testicular consistency and volume and presence of epididymis, vas deferens, and varicocele should be assessed.

15.5.3 Lab Tests

An endocrine evaluation based on serum testosterone and FSH levels helps to diagnose the majority of clinically significant endocrinopathies. If the testosterone level is low, complete evaluation including free and total testosterone, luteinizing hormone (LH), prolactin (PRL), inhibin B, and estradiol levels should be performed.

Semen analysis can reveal the nature of azoospermia via the evaluation of volume, pH, and fructose. The ejaculate volume is an essential tool in the evaluation of an azoospermic patient, differentiating distal seminal tract obstructions from proximal ones, considering that seminal fluid is mainly due to seminal vesicle production.

figure b

15.5.4 Genetic Screening

Karyotype, chromosome Y microdeletions, and CFTR gene mutations evaluations are advised for patients with azoospermia. Particularly, karyotype and chromosome Y microdeletion assessment must be done when NOA is suspected and in any case before assisted reproductive technique. Conversely, CFTR gene mutation screening is suggested in patients with obstruction. When assisted reproduction techniques (ART) are scheduled, screening should be extended to the partner, to define the risk of development of cystic fibrosis in the newborn.

15.5.5 Radiological Assessment

Testicular ultrasound adds information regarding structure of testicular tissue, testicular volume, epididymal aspect, and presence of varicocele or unpalpable tumor.

Transrectal ultrasound (TRUS) could be useful when ejaculate volume ≤1.5 mL and EjDO is suspected: obstruction should be suspected when seminal vesicle (SV) width is >1.5 cm and ejaculatory duct diameter is >2.3 mm or when cyst or duct calcification is observed [19]. However, TRUS did not show high specificity for EjDO diagnosis: only 50% of men need surgery based on TRUS findings.

Magnetic resonance imaging (MRI) is showed to be beneficial for soft-tissue and cystic lesions; however, it is expensive, time consuming, and accuracy is not greater than TRUS [20].

15.5.6 Invasive Diagnostic Tools

Seminovesciculography, vasography, testicular fine needle aspiration, open testicular biopsy, and transurethral cyst aspiration can be used to confirm the diagnosis. Today, they are hardly used for pure diagnostic purposes.

15.6 Surgical Treatment

Clinical management depends on etiology of azoospermia. Two main different options are available to procreate:

  • Surgical correction, with the goal to restore natural fertility and allow the couple to conceive naturally. It is a valid, and often preferred, option in selected cases of OA.

  • Sperm retrieval for assisted reproductive techniques (ART) purposes. It is the only option in case of NOA and in many cases of OA.

figure c

15.6.1 Recanalization of the Proximal Seminal Pathways

15.6.1.1 Vasoepididymostomy

This approach should be considered as first option when epididymal or vasal obstruction is present. The distal cauda epididymis represents the best site to perform the anastomosis due to presence of more robust tubules at this level and a long tract of epididymal tubule left for sperm maturation and motility acquirement. However, multifocal epididymal obstructions require that the anastomosis is performed proximally to all sites of obstruction. Proof of proximal patency is given by finding whole sperm in the open epididymal tubule. A standard microscope for sperm identification in the aspirated fluid is therefore necessary in the operating theatre.

Surgical technique consists in 3–4 cm vertical incision in the anterior aspect of the scrotum, preferably in the median raphe to expose the testis. The vas deferens is identified and transected close to the epididymal cauda. Several techniques have been described for microsurgical vasoepididymostomy, including end-to-side tubulovasostomy, triangulation, and tubular intussusception techniques [21]. However, the end-to-side anastomosis, firstly described by Thomas, is currently the most commonly used technique. It consists of a 1–2 mm incision of the epididymal tubule followed by a two-layer microsurgical anastomosis: a mucosal edge of 4–5 interrupted 10–0 nylon sutures and an additional 10–12 interrupted 9–0 nylon sutures for the outer muscular layer (Fig. 15.1).

Fig. 15.1
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End to side vasoepididymostomy

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Despite the operating microscope representing the gold standard to perform the procedure, robot-assisted surgery has been proposed, but its use is not widespread at present [22].

15.6.1.2 Vasovasostomy

It consists of an end-to-end anastomosis of the vasal stumps, after resection of the obstructed segment. Scrotal, inguinal, or infrapubic incision can be performed [23]. Adequate mobilization of the vas, without compromising vascularization, should be performed to ensure a tension-free anastomosis. However, in case of multifocal obstruction along the vas, recanalization is not indicated.

Most surgeons perform vasovasostomy using two-layer microsurgical anastomosis, described by Silber. Like the vasoepididymostomy technique, the procedure consists of 5–6 interrupted 10–0 nylon sutures in the inner mucosal edges of the vas deferens, followed by 10–12 additional interrupted 9–0 nylon sutures in the outer muscular layer (Fig. 15.2) [24]. A modified one-layer anastomosis using interrupted 9–0 nylon suture through the mucosal and muscular layers of the vas has also been described [25]. Again, a robotic vasovasostomy has also been proposed with apparently good results and very high costs (Video 15.6).

Fig. 15.2
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Microsurgical two-layer vasovasostomy

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The quality of the semen retrieved in the testicular stump represents the most important predictor of outcome and should be considered to assess the best surgical approach. Testicular vasal fluid has been graded according to the quality of the seminal fluid, as follow:

  • Grade 1: Prevalence of normal motile sperm.

  • Grade 2: Prevalence of normal nonmotile sperm.

  • Grade 3: Prevalence of sperm heads.

  • Grade 4: Only sperm heads.

  • Grade 5: Absence of sperm.

Vasovasostomy should be performed for grades 1–4 [26]. For grade 5 vasal fluid, vasovasostomy should be performed if the fluid is watery and copious. If the fluid is thick and creamy, successful rate of vasovasostomy is low and vasoepididymostomy should be considered, particularly when magnification reveals discolored or indurated area in the epididymis (tubule rupture due to back pressure) or demarcation between collapsed and dilated tubules.

Other variables to consider are obstructive interval, length of the testicular vasal stump, presence of sperm granuloma, prior vasectomy reversal, and surgeon skills [21].

Robot-assisted approach for scrotal or intra-abdominal vasovasostomy as an alternative to microsurgery has been applied to obviate the need for an operating microscope [27].

15.6.2 Recanalization of the Distal Seminal Pathways

Preoperative assessment is crucial to determine appropriate surgical approach. When prostatic cyst is diagnosed, the communication with the ejaculatory ducts should be evaluated.

15.6.2.1 Trans Rectal Ultrasound-Guided Cyst Aspiration (TRUCA)

It is the treatment of choice when a noncommunicating prostatic cyst determines an ab-extrinsic compression and obstruction of the ejaculatory ducts. Both transrectal and transperineal access have been described. The procedure is performed using a sterile disposable needle guidance device mounted over the ultrasound probe puncture; a fine needle (20–22-gauge, 200 mm-long) is inserted into the cyst under real-time ultrasound guidance (Fig. 15.3). Cyst fluid is aspirated and analyzed to evaluate the presence of sperm (400× magnification). Contrast agent is injected to determine the relation with ejaculatory ducts. If the diagnosis of noncommunicating cyst is confirmed (Fig. 15.4) by absence of sperm and radiologic imaging, cyst sclerotization using ethanol 90% is performed.

Fig. 15.3
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TRUCA: Ultrasonographic guidance of needle into the cyst

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Fig. 15.4
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TRUCA: Noncommunicating prostatic cyst

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15.6.2.2 Transurethral Resection of Ejaculatory Duct (TURED)

In 1973, Farley and Barnes first described stenosis of the ejaculatory duct (ED) and management with transurethral resection [27]. The rationale is to restore the continuity of the seminal ducts, through the resection of the intraprostatic tract of the ejaculatory ducts or the incision of an obstructing prostatic cyst. Surgical technique depends on obstruction etiology. When communicating cyst is diagnosed (Fig. 15.5), its anterior wall is incised using a Collings loop, allowing voiding of the cyst into the prostatic urethra (Video 15.4). Conversely, a “true” resection in performed in case of intrinsic obstruction/stenosis of the ejaculatory ducts, using a U loop. Prior injection of methylene blue into the seminal vesicles can help in identifying the ejaculatory ducts during resection. Simultaneous transrectal ultrasound control could be useful to perform the procedure in a safe manner (Video 15.5). In presence of extraprostatic stenosis or extended atresia of ejaculatory ducts, recanalization is not possible and indicated [28].

Fig. 15.5
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TRUCA: Prostatic communicating cyst. Injection of contrast through transperineal fine needle shows median prostatic cyst communicating with both seminal vesicles and vas deferens (arrows)

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15.6.3 Sperm Retrieval Techniques

Sperm retrieval techniques for intracytoplasmic sperm injection (ICSI) represent the only therapeutic option in patients with nonobstructive azoospermia (NOA), in those with untreatable obstructive azoospermia (OA), and in cases where female factors are present and require the use of ART. In case of OA, any sperm retrieval technique might be used, either percutaneous or open surgical (MESA; TESA; TESE; PESA), with high probability of obtaining the material needed for ICSI; on the contrary, in case of NOA, it is necessary to use open surgical techniques, TESE or Micro-TESE, with lower chances of success [29].

Obstructive Azoospermia

MESA

MICROsurgical Epididymal Sperm Aspiration

TESA/TEFNA

TESE

TEsticular sperm aspiration/fine needle

TEsticular sperm extraction

PESA

Percutaneous epididymal sperm aspiration

Nonobstructive azoospermia

TESE

TEsticular sperm extraction

Micro-TESE

MICROsurgical testicular sperm extraction

It should be noted that clinical situations might be complex and are best handled by an expert in the field, particularly on surgery of the male reproductive tract, no matter whether specialist in Andrology or Gynaecology. Techniques available today include:

15.6.3.1 MESA

MESA has been considered in the past the gold standard for spermatozoa collection in any cases of OA, as it allowed to obtain more than 1 million/mL sperm counts [30]. The original technique is rarely adopted today due to longer surgical times and higher costs. We developed a simplification of the original technique, named Mini-MESA, which combines the advantages of percutaneous and microsurgical surgery (x). It is performed through a window scrotal incision, allowing exposure of the epididymis head; at this level, the puncture is performed with an insulin needle under direct vision. This procedure allows to recover larger number of gametes, providing plenty of material for cryopreservation. Many studies have compared ICSI results using freshly retrieved or frozen-thawed sperm and the majority of these have concluded that there is no difference in terms of fertilization, implantation, and pregnancy rates [31].

15.6.3.2 TESA/TEFNA

This is the simplest percutaneous technique indicated in case of OA. It permits collection of spermatozoa for immediate ICSI and sometimes for one or more subsequent cycles.

This procedure consists in puncturing the testicle with a butterfly 21 G needle, followed by aspiration of the testicular fluid, which is then analyzed by biologist for retrieving spermatozoa. By maintaining aspiration during the extraction, it is often possible to remove a seminiferous tubule (Fig. 15.6), which is fragmented in a Petri plate for sperm extraction (Video 15.2).

Fig. 15.6
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Seminiferous tubule obtained by aspiration during TESA

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15.6.3.3 PESA

This procedure is similar to TESA, differing only for sampling site, which in this case is represented by the head of the epididymis (Fig. 15.7). The number of gametes that can be obtained is generally higher than TEFNA technique and it is almost always possible to freeze the sample for subsequent cycles. PESA is particularly indicated in case of vas deferens agenesis and in all the other situations where a surgical restoration of the seminal tract is not possible.

Fig. 15.7
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Butterfly 21G needle inserted in the head of epididymis during PESA

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15.6.3.4 TESE

This technique is the gold standard in case of NOA. In this case, a surgical biopsy is performed, single or multiple (Fig. 15.8), monolateral or bilateral, with window technique (Fig. 15.9) or with delivery of the testicle. This procedure is more invasive, but allows a good amount of material to be obtained. It is therefore indicated when there is the possibility of cryopreservation, after failure of percutaneous techniques or when differential diagnosis between OA and NOA is not yet discovered. If no spermatozoa are found at first biopsy, multiple biopsies are taken at different testicular sites [32]. Sperm recovery rate in NOA is around 50–60% [33], in contrast to OA cases where gametes can be recovered in all patients [34]. The appropriate number of biopsies to be performed is variable, but studies have shown that if gametes are present, they are often found within the first 4 biopsies [35]. Approximately half of the cases with positive results occur on the first sample [36] (Video 15.3).

Fig. 15.8
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Multiple conventional TESE

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Fig. 15.9
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TESE: Window technique

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15.6.3.5 MICRO-TESE

This approach, also known as Microdissection TESE, proposed by Schlegel in 1999, presents, as important innovation, the use of an operating microscope for gamete retrieval, resulting in higher success rate and fewer complications compared to TESE with multiple biopsies [37]. It consists in a single equatorial incision of the tunica albuginea and opening of the testicle; then, single seminiferous tubules are sampled from different areas of the testicular parenchyma by using microsurgical forceps and an operating microscope, and then sent to the laboratory for spermatozoa extraction. Optical magnification of the microscope enables to recognize and collect seminiferous tubules of larger diameter (Fig. 15.10), more likely containing spermatozoa [38]. This scenario of focally dilated tubules, typical of some patients with incomplete Sertoli Cells Only Syndrome (SCOS), is unfortunately detectable in only 30% cases of NOA. At the end, the incision is closed with a running suture with minimal scarring (Video 15.1).

Fig. 15.10
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Micro-TESE in a Klinefelter patient. Area of dilated tubules is visible between the forceps tips

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The advantages of Micro-TESE over multiple TESE are: less vascular damage, minor tissue loss, less postoperative pain due to reduced retraction of the albuginea, and less compression of the testicular parenchyma [37]. According to literature, this technique is often chosen in case of failure of conventional TESE or in severe conditions of azoospermia (SCOS, Klinefelter’s syndrome) [32, 33]. Considering that in approximately 50% of naïve NOA cases, spermatozoa are recovered at the first biopsy, a ‘gradual’ Micro-TESE technique has been proposed by our group [39]. Under general or local anaesthesia (cord block and skin infiltration), an initial scrotal window incision is performed, similarly to traditional TESE, and a single testicular biopsy is extracted from mid-portion of the testis. The sample is immediately sent to the biological laboratory together with a specimen for histology and, if spermatozoa are found, the procedure is ended. If no spermatozoa are found, however, the incision is extended equatorially until the testis is fully opened and Micro-TESE is performed. In this way, a considerable saving of Micro-TESE procedures and consequent surgical invasiveness on testis may be achieved, with significant reduction in operating time and costs. This makes sense, if we consider that a significant hormonal impairment has been described after one or more Micro-TESE procedures [39, 40]. Histological examination is also highly desirable during TESE and Micro-TESE (at least one sample per testicle). This will provide useful prognostic information for possible re-interventions and may exclude intratubular germ cell neoplasia presence, a well-known possibility in azoospermic subjects, in consideration of the links between male infertility and germ cell neoplasia.

15.6.3.6 New Horizons

One of the major challenges in sperm retrieval surgery is represented by the preoperative prediction of successful sperm retrieval. Many predictive markers or models have been proposed such as histology, FSH, or other hormones levels and testicular volume, with debated values of efficacy. For the future, the presence of some omics in seminal plasma, particularly microRNA, appears particularly promising in detecting testes which contain areas of spermatogenesis [41].

Although micro-TESE has become first-line in sperm retrieval in men with NOA, there are some challenges with the procedure. For this reason, new interesting methods have been proposed: some of the latest advances on the horizon, such as multiphoton microscopy (MPM), Raman spectroscopy (RS), and full-field optical coherence tomography (FFOCT), have demonstrated the potential to better identify areas of spermatogenesis and improve sperm extraction success. Furthermore, ORBEYE (a novel 4 K three-dimensional [3D] surgical exoscope), Contrast Enhanced Ultrasonography (CEUS), and artificial intelligence have been mentioned, nowadays, as new strategies to enhance sperm retrieval for ART [42].

Although these new procedures seem to appear very sophisticated, showing higher magnification of the surgical field, faster operating time and, in some cases, less invasiveness, their reproducibility and higher costs and the absence of strong and solid human clinical trial indicate that their role in sperm retrieval surgery is still to be established.