Testicular fine needle aspiration: the alternative method for sperm retrieval in non-obstructive azoospermia

Aby Lewin1, Benjamin Reubinoff, Anat Porat-Katz, David Weiss, Vered Eisenberg, Revital Arbel, Hagar Bar-el and Anat Safran

IVF Unit, Department of Obstetrics and Gynecology, Hadassah-Hebrew University Medical Center, Ein-Kerem, Jerusalem, Israel


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The objective of this prospective open study was to determine the feasibility of obtaining mature spermatozoa for intracytoplasmic sperm injection (ICSI) by testicular fine needle aspiration (TEFNA) in men diagnosed with non-obstructive azoospermia. TEFNA consisted of a mean of 15 punctures and aspirations in each testis, using 23 gauge butterfly needles, connected to a 20 ml syringe with an aspiration handle. Patients (n = 85) underwent 111 TEFNA cycles. Mature testicular spermatozoa were recovered in 65 (58.5%) cycles from 50 (58.8%) patients. The sperm recovery rate by testicular histology was 14 out of 29 (48.3%) in patients with Sertoli cell-only, 13 out of 28 (46.4%) in patients with maturation arrest, 19 out of 20 (95%) in patients with hypospermatogenesis, four out of six (66.6%) in patients with tubular hyalinization due to non-mosaic Klinefelter's syndrome. No spermatozoa were found in two cases with post-irradiation fibrosis. ICSI was performed in all 65 cycles. In 58 cycles in which only the husbands' spermatozoa were used, 406 mature oocytes were injected, and 154 (37.9%) were normally fertilized. Of the 143 embryos that developed (92.8%), 119 were transferred in 42 cycles resulting in 18 clinical pregnancies (42.8%), with 31 gestational sacs, providing an implantation rate of 26%. One abortion of a singleton pregnancy occurred (5.6%). No major side-effects, such as haematoma or infection were recorded. In conclusion, we have found TEFNA to be efficient, easy to learn, safe and well tolerated by all patients. In our opinion, TEFNA should be considered the first choice whenever sperm recovery is attempted in patients with non-obstructive azoospermia.

Key words: fine needle aspiration/ICSI/non-obstructive azoospermia


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
In-vitro fertilization (IVF) was originally developed for patients with tubal infertility. In recent years, assisted reproductive techniques have been more oriented towards the treatment of male infertility. The introduction of intracytoplasmic sperm injection (ICSI) (Palermo et al., 1992Go) has resulted in a great enhancement of fertilization and pregnancy rates in patients with severely reduced sperm quality (Van Steirteghem, et al., 1993Go). The availability of ICSI enabled the first attempts of oocyte fertilization by testicular spermatozoa in non-obstructive azoospermic patients, leading to viable pregnancies (Yemini et al., 1995Go; Gil-Salom et al., 1995Go). Nevertheless, the first report of a successful prospective series of attempts at testicular sperm retrieval in non-obstructive azoospermia (Devroey et al., 1995Go), was followed by several studies analysing the efficacy of ICSI with testicular sperm extraction (TESE) using open biopsies, in non-obstructive azoospermia, all reporting high sperm recovery, fertilization and pregnancy rates (Tournaye et al., 1995Go, 1996aGo; Devroey et al., 1996Go; Kahraman et al., 1996aGo,bGo; Silber et al., 1996Go; Friedler et al., 1997Go). And yet, testicular open biopsies have considerable side-effects, including haematomas, inflammation and even permanent devascularization of the testis resulting in testicular atrophy (Schlegel and Su, 1997Go) to occur following TESE procedures with multiple biopsies. The hypothesis of the present study was that in some cases of testicular failure, due to the focal nature of sperm production (Levin, 1979Go), the testicular fine needle aspiration (TEFNA) approach may enable the operator to reach more testicular sites, including those located within the testis, without causing extensive testicular damage and consequently with lesser side-effects. The study evaluates the feasibility and safety of TEFNA in the recovery of spermatozoa for ICSI in various aetiologies of non-obstructive azoospermia.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Patients
A total of 85 couples in whom the male partner was diagnosed as suffering from non-obstructive azoospermia were included in the study. The mean age of the male patients was 32.6 years (range 25–44 years) and of the female partners 32.2 years (range 21–44). The mean duration of infertility 7.4 years (range 1–18). The mean serum follicle stimulating hormone (FSH) was 18.1 mIU/ml (range 2–55), although 29 men (34.1%) had normal (<10 mIU/ml) FSH concentrations. Absolute ejaculatory azoospermia was confirmed by rigorous search for spermatozoa in the ejaculate on three separate occasions prior to surgery, including the morning of oocyte retrieval, by high velocity centrifugation of the ejaculate at 1800 g for 5 min, dissolving the pellet in 50 µl of medium, and searching for spermatozoa microscopically in 5 µl droplets. All patients were karyotyped, 79 patients were 46,XY and six patients were found to be non-mosaic 47,XXY (Klinefelter's syndrome) and offered genetic counselling prior to treatment. The diagnosis of non-mosaic Klinefelter's syndrome was established after the analysis of at least 30 metaphases. Patients were classified by testicular histology, established by formal pre-treatment bilateral testicular biopsies, into Sertoli cell-only (germ cell aplasia) in 29 (34.1%) cases, maturation (spermatogenic) arrest in 28 (32.9%) cases, hypospermatogenesis (germ cell hypoplasia) in 20 (23.5%) cases, tubular hyalinization due to non-mosaic Klinefelter's syndrome (47,XXY) in six (7%) cases and post-irradiation fibrosis in two (2.3%) cases. It should be emphasized that only pure cases of Sertoli cell-only and maturation arrest were considered in these two groups and whenever the histological report described a mixed finding, i.e. almost complete maturation arrest or Sertoli cell-only with a focus of spermatogenesis, these cases were included in the hypospermatogenesis group.

Oocyte retrieval and insemination
Ovarian stimulation included a long protocol of gonadotrophin-releasing hormone (GnRH) agonist, using nafarelin acetate (Synarel, Teva, Petah-Tikva, Israel) 600 mcg/day by nasal spray, from the 21st day of the cycle, and human urinary follicle stimulating hormone (uFSH, Metrodin, Teva), started 14 days later. Oocyte retrieval was performed 34–36 h after human chorionic gonadotrophin (HCG; Chorigon, Teva) was administered i.m., under transvaginal ultrasound guidance and sedation-analgesia. Oocytes were incubated in human tubal fluid (HTF) medium, supplemented with 7.5% synthetic serum supplement (SSS; Irvine Scientific, Santa Ana, CA, USA). In preparation for ICSI, the surrounding cumulus cells were removed 2 h after oocyte retrieval using hyaluronidase (Type VII, Sigma, St. Louis, MO, USA), 60 IU/ml. ICSI was performed on the heated stage of an inverted microscope (Nikon Diaphot; Nikon, Tokyo, Japan), equipped with Leitz mechanical manipulators. Ready-made injection (Swemed, Uppsala, Sweden) and holding pipettes (Cook, Brisbane, QL, Australia) were used. The injection dish included three drops of the final sperm suspension, three drops of 10% polyvinylpyrrolidone (PVP; Sigma) and three drops of the injection medium (HTF–HEPES with 6% SSS), all covered with pre-equilibrated paraffin oil (Sigma). To facilitate the extraction of sperm cells, as the sperm pellet drops were engorged with blood cells and cell debris, the injection pipette was filled with PVP prior to sperm aspiration into the pipette. The spermatozoa recovered were rinsed and immobilized in the PVP drop and directly injected into the oocytes. Oocytes were then placed in drops of HTF–7.5% SSS for further incubation.

Sperm collection and preparation
TEFNA was performed immediately following oocyte retrieval under light general anaesthesia. The scrotal area was cleaned with 0.5% chlorohexidine solution and sterile draped. Standing to the left of the patient, the testis was grasped with the fingers of the left hand while the butterfly needle was held between the thumb and index fingers of the right hand. A single gentle slow pass in and out puncture and aspiration was performed in the caput of the epididymis on each side followed by immediate microscopic search of the aspirate to rule out the presence of spermatozoa. In the absence of spermatozoa in the epididymal aspirate, multiple punctures (mean of 15, range 10–20 per testis) and aspirations were performed systematically throughout the whole testis on both sides while squeezing and holding the testis firmly in position between the operators fingers throughout the entire aspiration, so that the aspirated locations are clearly plotted. Every testicular puncture was composed of multiple in and out movements in all directions until the yellowish fluid so aspirated ceased to flow or if bloody fluid appeared. The tubing was then occluded with an artery forceps and the needle removed from the testis. The operation came to an end once no more testicular fluid was aspirated or when all the aspirates started to be bloody. The set-up for both epididymal and testicular punctures included 23 gauge butterfly needles connected to a 20 ml syringe, installed in an aspiration handle (Cook, USA) for the application of a steady negative pressure. Following each puncture, the needle end of the tube was cut with scissors and the tube's contents rinsed using a 20 ml syringe filled with HTF–HEPES medium (Irvine Scientific) supplemented with 0.4% human serum albumin (Sigma). Medium (~0.5 ml) was flushed into one well of a 4-well plate (Nunc, Copenhagen, Denmark). A new butterfly needle was used for each puncture and punctures continued as long as yellowish, non-bloody fluid continued to flow into the tubing. The testicular aspirates were examined after every four punctures filling a 4-well plate under an inverted microscope (Nikon Diaphot) at x200 magnification and whenever sperm cells were noted, further aspirations in the same testicular area were performed. Samples from the wells in which sperm cells were observed were all collected before centrifugation into a common 15 ml conical test tube (Falcon, Becton Dickinson, Lincoln Park, NJ, USA) while all the other wells in which sperm cells were not observed in the initial inspection were collected in another 15 ml conical test tube. Both tubes were then centrifuged at 1800 g for 5 min. The final sperm suspension was achieved by resuspending the pellet in 50 µl of HTF–7.5% SSS. Erythrocyte lysing buffer (Nagy et al., 1997Go) was used in a few cases when the pellet was contaminated with red blood cells to the extent of not being able to search for sperm cells. Finally, microdroplets of 2 µl were placed on a dish under mineral oil for the microscopic search at x200 to x400 magnification.

Embryonic development and transfer
Fertilization was assessed 18 h after ICSI and confirmed by the detection of two clearly distinct pronuclei (2PN). Embryonic development was evaluated 24 h later. The embryos were scored for quality according to the homogeneity of the blastomeres and the degree of anucleated fragments (Staessen et al., 1989Go). Embryo transfer was performed 48–72 h after oocyte retrieval, using a Casmed catheter (Casmed, Banstead Surrey, UK), loaded with 10–15 µl culture medium. Supplementary embryos were cryopreserved. Micronized progesterone in the form of vaginal tablets (Dizengoff Pharmaceuticals, Tel Aviv, Israel) 50 mg, twice daily, were used to support the luteal phase, supplemented, when needed according to serum 17ß-oestradiol and progesterone concentrations on days 4, 8 and 12 following embryo transfer, with i.m. injections of HCG (Chorigon; Teva), 2500 IU.

Statistical analysis
Statistical analyses were performed using Fisher's exact test.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
TEFNA resulted in the recovery of mature spermatozoa in 65 of 111 (58.6%) cycles and in 50 of the 85 (58.8%) men (Table IGo). No sperm cells were recovered in any of the epididymal aspirations, thus corroborating the diagnosis of non-obstructive azoospermia. Only single spermatozoa (up to 10) were recovered in 30 (46.2%) cycles, tens of spermatozoa were recovered in 26 (40.0%) cycles and hundreds to thousands were recovered in nine (13.8%) cycles. The sperm recovery rate by testicular histology was 14 out of 29 (48.3%) in the patients with Sertoli cell-only, 13 out of 28 (46.4%) in maturation arrest, 19 out of 20 (95%) in hypospermatogenesis, four out of six (66.6%) in the patients with tubular hyalinization (Klinefelter`s syndrome). No spermatozoa were found in the two cases with post-irradiation fibrosis (Table IIGo).


View this table:
[in this window]
[in a new window]
 
Table I. Results of testicular fine needle aspiration (TEFNA) in the recovery of testicular spermatozoa
 

View this table:
[in this window]
[in a new window]
 
Table II. Sperm recovery rates by testicular histological classification
 
A mean of 9.6 ± 6.1 mature oocytes was collected per cycle, and ICSI was performed on 434 mature oocytes (mean 6.8 ± 4.1 per cycle) of the 65 cycles in which spermatozoa were found. In 58 cycles only husbands' spermatozoa were injected. In another seven cycles in all of which oocytes outnumbered the available husbands' spermatozoa, donor spermatozoa were injected into the remaining oocytes, at the patients' request. In the 58 cycles where only husbands' spermatozoa were used, 406 mature oocytes were injected, and 154 (37.9%) oocytes were normally fertilized (Table IIIGo). Of the 143 embryos that developed, 119 were transferred in 42 cycles (mean 2.83 ± 1.7 per cycle), resulting in 18 clinical pregnancies with 31 gestational sacs, providing a pregnancy rate per transfer of 42.8% and an implantation rate of 26%. In one case of non-mosaic Klinefelter's syndrome, previously reported (Reubinoff et al., 1998Go), pregnancy was achieved after preimplantation genetic diagnosis. Pregnancies consisted of nine singletons, five twins and four triplets. One abortion of a singleton pregnancy was recorded (5.6%). When the results of ICSI with the husbands' spermatozoa were classified by the number of spermatozoa recovered, significantly lower fertilization rates and transfers per cycle rates were noted in the group where fewer than 10 spermatozoa were retrieved, in comparison with the other groups (Table IVGo), although the pregnancy and implantation rates were similar between groups. When comparing among the above groups the fertilization rates when using for ICSI testicular motile or non-motile spermatozoa, the results with motile spermatozoa were significantly higher only in the group where more than 100 spermatozoa were retrieved (Table VGo).


View this table:
[in this window]
[in a new window]
 
Table III. Results of intracytoplasmic sperm injection (ICSI) with the husband's spermatozoa (58 cycles)
 

View this table:
[in this window]
[in a new window]
 
Table IV. Results of intracytoplasmic sperm injection (ICSI) with the husbands' spermatozoa classified by the number of spermatozoa recovered. Values in parentheses are percentages
 

View this table:
[in this window]
[in a new window]
 
Table V. Fertilization rates with motile spermatozoa, compared with non-motile spermatozoa, classified by the number recovered. Values in parentheses are percentages
 
In two of the seven mixed cycles, embryos achieved from donor insemination were transferred, at the couples request, along with those originating from the husband's spermatozoa, accounting for an additional pregnancy.

Excess testicular spermatozoa were cryopreserved in 27 cycles and later thawed and used for fertilization in 22 cycles so far. In 18 cycles, embryos were available for transfer although in two cycles the embryos failed to progress and were not transferred. Three pregnancies (18.7%) were achieved following 16 transfers, resulting in the births of two healthy girls and one ongoing pregnancy.

Following TEFNA, patients were released after 2–5 h, resuming their normal activities. No haematoma, infection or other serious side-effects were reported following TEFNA. The only complaints were pain that lasted 3 days in three patients and treated with oral analgesics after physical examination, testicular Doppler ultrasound and blood tests were normal.


    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Evaluation of spermatogenesis and fertility potential in cases of azoospermia with the use of testicular aspiration biopsy was first reported in 1965 (Obrant and Persson, 1965Go). This was followed by other reports (Persson et al., 1971Go; Kaufman and Nagler, 1987Go; Gottschalk-Sabag et al., 1993Go; Craft et al., 1997Go), which defined the criteria for using TEFNA as a routine diagnostic method in the evaluation of infertility, suggesting this procedure to be of value in the qualitative and quantitative evaluation of testicular morphology and spermatogenesis. Histological analysis of the testes in patients with various aetiologies of non-obstructive azoospermia demonstrated that occasional foci of normal spermatogenesis will be found in many of the cases (Levin, 1979Go; Silber et al., 1995). This fact was the basis for the first reports on successful sperm recovery by testicular sperm extraction (TESE) in patients with non-obstructive azoospermia. Fertilization following the injection of few spermatozoa obtained by open testicular biopsy in an azoospermic patient with almost complete spermatogenic arrest and testicular tubular atrophy was reported (Yemini et al., 1995Go). In another case the recovery of a few spermatozoa in a man with Sertoli cell-only syndrome with focal spermatogenesis was reported (Gil-Salom et al., 1995Go), and a pregnancy was achieved. Concomitantly with these studies, the efficacy of ICSI with TESE was analysed in a series of 15 patients with non-obstructive azoospermia (Devroey et al., 1995Go). High sperm recovery rate was reported (86%) and the fertilization (47.8%) and pregnancy (25%) rates achieved were remarkably similar in those patients to those obtained using testicular spermatozoa from patients with normal spermatogenesis (Devroey et al., 1994Go). Following this initial study, more experience has been reported using TESE and ICSI for the treatment of non-obstructive azoospermic patients (Tournaye et al., 1995Go, 1996aGo; Kahraman et al., 1996aGo,bGo; Devroey et al., 1996Go; Silber et al., 1996Go; Friedler et al., 1997Go). Following previous experience with surgical retrieval of spermatozoa in cases of obstructive azoospermia with the use of percutaneous epididymal fine needle sperm aspiration (Shrivastav et al., 1994Go), the first clinical application of TEFNA for the recovery of mature spermatozoa in non-obstructive azoospermia was reported by our group (Lewin et al., 1996Go), and a pregnancy resulting in a birth was achieved. Recently, the efficacy, albeit lower than that of open biopsy, was demonstrated (Tournaye et al., 1998Go) of a single fine needle puncture and aspiration in recovering testicular spermatozoa in cases of normal spermatogenesis. Our hypothesis was that compared to the TESE approach, the fine needle approach may enable the operator to reach deeper testicular sites and thus increase the chance of hitting a rare site of active spermatogenesis. Based on this hypothesis, we have initiated the present prospective study in which TEFNA was applied to all non-obstructive azoospermic patients. We have shown that a high success rate in sperm recovery can be achieved in most histological variants of non-obstructive azoospermia, as 85 patients underwent 111 treatment cycles and mature spermatozoa could be recovered in 65 (58.6%) cycles in 50 (58.8%) patients. High pregnancy (42%) and implantation (26%) rates per transfer were achieved, demonstrating that once spermatozoa are retrieved, the implantation and pregnancy rates are comparable to those achieved by other sperm retrieval methods and to ICSI results with ejaculated spermatozoa. Nevertheless, treatment outcome was found to be related to the number of spermatozoa recovered, as the fertilization and transfer rates were lower in the group of men with poor sperm retrieval (<10 spermatozoa) as compared to the other groups. A high sperm retrieval rate (66.6%) was observed in Klinefelter's syndrome patients, corroborating previous reports on successful sperm recovery in some 47,XXY Klinefelter's patients (Tournaye et al., 1996bGo). On the other hand, one should bear in mind the potential risk of chromosomal abnormalities in the offspring of these men, and genetic counselling together with preimplantation genetic diagnosis should be offered to them (Tournaye et al., 1996bGo; Reubinoff et al., 1998Go).

Our study did not compare the efficacy of testicular sperm retrieval by FNA with that of TESE by open biopsies. Nevertheless, comparisons between open and percutaneous needle biopsies in men with azoospermia (Rosenlund et al., 1998Go) have shown that needle biopsies using 19 gauge needles were inferior to open biopsy for histopathological evaluation, but when testicular material was obtained, it was as good as open biopsy in terms of determining the presence of spermatozoa. The results with 21 gauge needles were inferior to open biopsy in both parameters. The authors concluded that percutaneous biopsy with a 19 gauge butterfly needle is a quick and reliable method for demonstrating spermatozoa for ICSI. In another study (Friedler et al., 1997Go) spermatozoa were recovered in 16 out of 37 patients (43%) by open biopsies, compared to four of 37 patients (11%) by TEFNA. Such poor results may be related to the limited number of punctures, as only six were performed in one testicle. Furthermore, the multiple-step sperm preparation including Percoll gradient separation and two additional washing steps described by this group is unsuitable, in our opinion, for this purpose as it is bound to cause loss of spermatozoa during the various steps and when only few are present this may result in failure of sperm recovery. The preparation protocol we use for testicular spermatozoa includes only one step of high-speed (1800 g for 5 min) centrifugation and the search takes place in 2 µl microdroplets.

Although the ultimate choice of testicular sperm retrieval methods will depend on a number of factors including the clinical diagnosis, patients preference and the availability of the necessary surgical skills, one of the most important parameters will be the physiological consequences of these techniques on testicular function. In a recent study (Schlegel and Su, 1997Go), the effects of TESE on the testis of 64 patients were evaluated. Of patients, 82% had intratesticular abnormalities present on ultrasound, suggestive of persistent haematoma and/or inflammation as long as 3 months following TESE. The majority of these lesions were transient and appeared to resolve by 6 months after the operation. However, permanent devascularization of the testis was shown to occur following TESE procedures with multiple biopsies. Another study (Harrington et al., 1996Go) demonstrated sonographic evidence of intratesticular bleeding in four out of 58 (7%) percutaneous biopsies performed with an 18 gauge biopsy needle, resolving within 6 months post-operatively. On the other hand, in the study by Watkins and co-workers who applied fine needle biopsy, as well as in our study, no major complications were recorded, beside mild pain and discomfort requiring simple analgesics (Watkins et al., 1997Go). In the present study, a very low rate of minor complaints was recorded (3/85; 3.5%), all three cases presenting only pain that was treated by oral analgesics after physical examination, testicular Doppler ultrasound and blood count were normal. However, a comparative analysis on the long-term effects of these techniques as revealed by extensive sonography is warranted.

Following TEFNA we were also able to cryopreserve spare testicular spermatozoa in 27 cycles and three pregnancies (18.7%) were achieved so far following 16 transfers, resulting in the births of two healthy girls and one ongoing pregnancy. This is in agreement with a previous observation (Verheyen et al., 1997Go) which found that, despite the low quality of the fresh testicular spermatozoa, a high percentage of frozen–thawed testicular spermatozoa survive and are capable of successfully fertilizing mature oocytes.

Finally, our results support the conclusion of previous studies that testicular sperm search should be offered to all azoospermic patients, irrespective of FSH concentrations, testicular size, medical history and testicular histology (Tournaye et al., 1995Go, 1996aGo, 1997Go; Kahraman et al., 1996aGo,bGo). Our results also demonstrate high rates of sperm recovery in patients with Sertoli cell-only or maturation arrest, where previous diagnostic histology failed to demonstrate the presence of mature spermatozoa. This fact underlines the shortcomings of a single, or even several testicular specimens for making a correct histological diagnosis and emphasizes, in our opinion, the focal nature of spermatogenesis in these patients. This concept of focal distribution was challenged recently by Silber et al., who postulated that a rather homogeneous distribution of spermatogenesis exists in non-obstructive azoospermia (Silber et al., 1997Go). Nevertheless, we have documented that in most cases where only a few spermatozoa were recovered, these were observed in only one or two of many wells of the fresh preparation examined on-line for the presence of spermatozoa, while all other wells were devoid of spermatozoa.

In conclusion, TEFNA was shown to be a successful approach for collecting mature spermatozoa in the majority of cases with non-obstructive azoospermia. The technique is easy to learn and allows the operator the possibility of reaching multiple intratesticular sites and increases the chances of retrieving spermatozoa for ICSI, almost without reduction in testicular volume. The procedure was also found to be safe and well tolerated by all patients. In our opinion, until exclusion criteria are defined, no case should be considered hopeless and refused a testicular sperm recovery attempt, and TEFNA should be considered the first choice for sperm recovery attempts.


    Notes
 
1 To whom correspondence should be addressed Back


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Craft, I., Tsirigotis, M., Courtauld, E. and Farrer-Brown, G. (1997) Testicular needle aspiration as an alternative to biopsy for the assessment of spermatogenesis. Hum. Reprod., 12, 1483–1487.[Abstract]

Devroey, P., Liu, J., Nagy, Z. et al. (1994) Normal fertilization of human oocytes after testicular sperm extraction and intracytoplasmic sperm injection (TESE-ICSI). Fertil. Steril., 62, 639–641.[ISI][Medline]

Devroey, P., Liu, J., Nagy, Z. et al. (1995) Pregnancies after testicular sperm extraction and intracytoplasmic sperm injection in non-obstructive azoospermia. Hum. Reprod., 10, 1457–1460.[Abstract]

Devroey, P., Nagy, P., Tournaye, H. et al. (1996) Outcome of intracytoplasmic sperm injection with testicular spermatozoa in obstructive and non-obstructive azoospermia. Hum. Reprod., 11, 1015–1018.[Abstract]

Friedler, S., Raziel, A., Strassburger, D. et al. (1997) Testicular sperm retrieval by percutaneous fine needle aspiration compared with testicular sperm extraction by open biopsy in men with non-obstructive azoospermia. Hum. Reprod., 12, 1488–1493.[Abstract]

Gil-Salom, M., Remohi, J., Miguez, Y. et al. (1995) pregnancy in an azoospermic patient with markedly elevated serum follicle stimulating hormone levels. Fertil. Steril., 64, 1218–1220.[ISI][Medline]

Gottschalk-Sabag, S., Glik, T., Bar-On, E. and Weiss, D.B. (1993) Testicular fine needle aspiration as a diagnostic method. Fertil. Steril., 59, 1129–1131.[ISI][Medline]

Harrington, T.G., Schauer, D. and Gilbert, B.R. (1996) Percutaneous testis biopsy: an alternative to open testicular biopsy in the evaluation of the subfertile man. J. Urol., 156, 1647–1651.[ISI][Medline]

Kaufman, D.G. and Nagler, H.M. (1987) Aspiration flow cytometry of the testes in the evaluation of spermatogenesis in the infertile male. Fertil. Steril., 48, 287–291.[ISI][Medline]

Kahraman, S., Ozgur, S., Alatas, C. et al. (1996a) Fertility with testicular sperm extraction and intracytoplasmic sperm injection in non-obstructive azoospermic men. Hum. Reprod., 11, 756–760.[Abstract]

Kahraman, S., Ozgur, S., Alatas, C. et al. (1996b) High implantation and pregnancy rates with testicular sperm extraction and intracytoplasmic sperm injection in obstructive and non-obstructive azoospermia. Hum. Reprod., 11, 673–676.[Abstract]

Levin, H.S. (1979) Testicular biopsy in the study of male infertility. Its current usefulness, histologic techniques and prospects for the future. Hum. Pathol., 10, 569–584.[ISI][Medline]

Lewin, A., Weiss, D.B., Friedler, S. et al. (1996) Delivery following intracytoplasmic injection of mature sperm cells recovered by testicular fine needle aspiration in a case of hypergonadotropic azoospermia due to maturation arrest. Hum. Reprod., 11, 769–771.[Abstract]

Nagy, Z.P., Verheyen, G., Tournaye, H. et al. (1997) An improved treatment procedure for testicular biopsy specimens offers more efficient sperm recovery: case series. Fertil. Steril., 68, 376–379.[ISI][Medline]

Obrant, K.O. and Persson, P.S. (1965) Cytological study of the testis by aspiration biopsy in the evaluation of fertility. Urol. Int., 20, 176–189.[ISI][Medline]

Palermo, G., Joris, H., Devroey, P. and Van Steirteghem, A. (1992) Pregnancies after intracytoplasmic sperm injection of single spermatozoon into an oocyte. Lancet, 340, 17–18.[ISI][Medline]

Persson, P.S., Ahren, C. and Obrant, K.O. (1971) Aspiration biopsy smear of testis in azoospermia. Cytological versus histological examination. Scand. J. Urol. Nephrol., 5, 22–26.[Medline]

Reubinoff, B.E., Abeliovich, D., Werner, M. et al. (1998) A birth in non-mosaic Klinefelter's syndrome after testicular fine needle aspiration, intracytoplasmic sperm injection and preimplantation genetic diagnosis. Hum. Reprod., 13, 1887–1892.[Abstract]

Rosenlund, B., Kvist, U., Ploen, L. et al. (1998) A comparison between open and percutaneous needle biopsies in men with azoospermia. Hum. Reprod., 13, 1266–1271.[Abstract]

Schlegel, P. and Su, L. (1997) Physiological consequences of testicular sperm extraction. Hum. Reprod., 12, 1688–1692.[Abstract]

Shrivastav, P., Nadkarni, P., Wensvoort, S. and Craft, I. (1994) Percutaneous epididymal sperm aspiration for obstructive azoospermia. Hum. Reprod., 9, 2058–2061.[Abstract]

Silber, S.J., Van Steirteghem, A. and Devroey, P. (1995b) Sertoli cell-only revisited. Hum. Reprod., 10, 1031–1032.[ISI][Medline]

Silber, S.J., Van Steirteghem, A., Nagy, Z. et al. (1996) Normal pregnancies resulting from testicular sperm extraction and intracytoplasmic sperm injection for azoospermia due to maturation arrest. Fertil. Steril., 66, 110–117.[ISI][Medline]

Silber, S.J., Nagy, Z., Devroey, P. et al. (1997) Distribution of spermatogenesis in the testicles of azoospermic men: the presence or absence of spermatids in the testes of men with germinal failure. Hum. Reprod., 12, 2422–2428.[Abstract]

Staessen, C., Camus, M., Khan, I. et al. (1989) An 18-month survey of infertility treatment by in vitro fertilization, gamete and zygote intrafallopian transfer and replacement of frozen-thawed embryos. J. In Vitro Fertil. Embryo Transfer, 6, 22–29.[ISI][Medline]

Tournaye, H., Camus, M., Goossens, A. et al. (1995) Recent concepts in the management of infertility because of non-obstructive azoospermia. Hum. Reprod., 10 (Suppl. 1), 115–119.[ISI][Medline]

Tournaye, H., Liu, J., Camus, M. et al. (1996a) Correlation between testicular histology and outcome after intracytoplasmic sperm injection using testicular spermatozoa. Hum. Reprod., 11, 127–132.[Abstract]

Tournaye, H., Staessen, C., Liebaers, I. et al. (1996b) Testicular sperm recovery in, 47,XXY Klinefelter patients. Hum. Reprod., 11, 1644–1649.[Abstract]

Tournaye, H., Verheyen, G., Nagy, P. et al. (1997) Are there any predictive factors for successful testicular sperm recovery in azoospermic patients? Hum. Reprod., 12, 80–86.[ISI][Medline]

Tournaye, H., Clasen, K., Aytoz, A. et al. (1998) Fine needle aspiration versus open biopsy for testicular sperm recovery: a controlled study in azoospermic patients with normal spermatogenesis. Hum. Reprod., 13, 901–904.[Abstract]

Yemini, M., Vanderzwalmen, P., Mukaida, T. et al. (1995) Intracytoplasmic sperm injection, fertilization and embryo transfer after retrieval of spermatozoa by testicular biopsy for an azoospermic male with testicular tubular atrophy. Fertil. Steril., 63, 1118–1120.[ISI][Medline]

Van Steirteghem, A.C., Nagy, Z., Joris, H. et al., (1993) High fertilization and implantation rates after intracytoplasmic sperm injection. Hum. Reprod., 8, 1061–1066.[Abstract]

Verheyen, G., Nagy, Z., Joris, H. et al. (1997) Quality of frozen–thawed testicular sperm and its preclinical use for ICSI into in-vitro matured germinal vesicle stage oocytes. Fertil. Steril., 67, 74–80.[ISI][Medline]

Watkins, W., Nieto, F., Bourne, H. et al. (1997) Testicular and epididymal sperm in a microinjection program: methods of retrieval and results. Fertil. Steril., 67, 527–535.[ISI][Medline]

Submitted on August 19, 1998; accepted on March 11, 1999.