What is the success rate of microtese (microsurgical testicular sperm extraction) in cases of non-obstructive azoospermia and what factors increase the rate of success?

Microdissection Testicular Sperm Extraction Success Rates and Factors in Non-Obstructive Azoospermia

Microdissection testicular sperm extraction (micro-TESE) yields successful sperm retrieval in approximately 46-50% of men with non-obstructive azoospermia (NOA), with significantly higher success rates compared to conventional TESE. 1, 2

Success Rates of Micro-TESE in NOA

• Micro-TESE is considered the gold standard method for surgical sperm retrieval in NOA patients, with sperm retrieval rates of approximately 46-50% 2
• Meta-analyses demonstrate that micro-TESE results in successful sperm extraction approximately 1.5 times more often than conventional non-microsurgical testicular sperm extraction 2
• In direct comparative studies, micro-TESE has shown significantly higher sperm retrieval rates (56.9%) compared to conventional TESE (38.2%) 3
• The success rate is particularly improved in patients with Sertoli-cell-only syndrome, with sperm retrieval rates of 26.9% for micro-TESE versus only 6.2% for conventional TESE 3

Factors That Increase Success Rates

Testicular Histology

• Testicular histology is one of the strongest predictors of successful sperm retrieval 1, 2
• Hypospermatogenesis pattern has the highest success rates (84-92.9%), followed by maturation arrest (27.3-36.4%), and Sertoli cell-only syndrome (6.2-26.9%) 3
• The presence of hypospermatogenesis at testicular biopsy is associated with good accuracy in predicting positive sperm retrieval after TESE compared to maturation arrest pattern or Sertoli cell-only syndrome 1

Hormonal Parameters

• Lower FSH levels are associated with higher sperm retrieval rates 3, 4
• Total testosterone and inhibin B levels are considered influential preoperative factors for successful sperm retrieval 4
• A prediction formula using FSH, total testosterone, and inhibin B levels has been developed to calculate the probability of successful outcome with sensitivity of 71.0% and specificity of 71.4% 4

Anatomical Factors

• Larger testicular volume (>12.5 ml) is associated with improved sperm retrieval success 5, 3
• The ability to identify enlarged seminiferous tubules during micro-TESE significantly increases success rates - when a clear microscopic distinction between enlarged and collapsed seminiferous tubules is visible, sperm retrieval is successful in nearly all cases 6

Genetic Factors

• Absence of complete AZFa and AZFb Y-chromosome microdeletions is associated with better outcomes 1, 5
• Complete AZFa and AZFb microdeletions predict extremely poor prognosis for sperm retrieval, with success rates approaching zero 1, 5
• Patients with Klinefelter syndrome have reduced sperm retrieval success compared to other NOA patients 5

Surgical Technique

• Operative microscopy allows for identification of seminiferous tubules that are more likely to harbor sperm, increasing retrieval success while minimizing tissue damage 2
• Wide opening of the tunica albuginea to examine multiple regions of testicular tissue increases the chance of finding isolated foci of spermatogenesis 2
• Extensive search of nearly all areas of the testis with limited risk of devascularization improves outcomes 2

Clinical Considerations

• Micro-TESE has lower complication rates (including hematoma and fibrosis) compared to conventional TESE 1, 2
• Recovery of baseline testosterone levels at long-term follow-up has been observed after both procedures, but micro-TESE has less effect on testosterone levels 1, 2
• Sperm retrieval and cryopreservation may be done prior to assisted reproductive technology procedures, as there are generally no substantial differences in ICSI success rates between fresh and cryopreserved sperm 2
• When sperm are successfully retrieved, ICSI can result in normal fertilization rates of approximately 64% and embryo cleavage rates of 75% 6

Cautions and Limitations

• No single predictor or combination of predictors provides definitive information about the chances of harvesting sperm in men with NOA, except for Y chromosome microdeletions in regions AZFa/b 5
• Even in patients with previous failed retrievals or unfavorable histologic results, micro-TESE may still be successful in up to 50% of cases 6
• Salvage micro-TESE has been shown to successfully retrieve sperm in 46.5% of patients with prior failed conventional TESE or testicular sperm aspiration 1