Ultrasonographic caput epididymis diameter is reduced in non-obstructive azoospermia compared with normozoospermia but is not predictive for successful sperm retrieval after TESE.

STUDY QUESTION Is the ultrasonographic determination of the caput epididymis diameter predictive for sperm retrieval after testicular sperm extraction (TESE) in non-obstructive azoospermia (NOA)? SUMMARY ANSWER Ultrasonographic determination of the caput epididymis diameter did not give any relevant clinical information in NOA and was not predictive for positive sperm retrieval after TESE. WHAT IS KNOWN ALREADY The diameter of the caput epididymis in ultrasonography (US) has a diagnostic relevance in azoospermic men to correctly identify obstructive azoospermia; however, its clinical value in NOA is not yet determined. STUDY DESIGN, SIZE, DURATION We performed a retrospective study of 100 azoospermic and 160 normozoospermic men attending a university infertility clinic. PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were submitted to scrotal US to determine the mean value of bilateral testicular volumes (ml), the bilateral longitudinal caput diameter (mm) and the antero-posterior diameter of the corpus (mm) epididymis. The number of spermatozoa retrieved after TESE and the testicular histology of azoospermic men was obtained and the percentage of seminiferous tubules with elongated spermatids (%T) was used to classify cases with normal spermatogenesis (obstructive azoospermia) (OA) (n = 20; %T ≥ 80) or with NOA (n = 80; %T < 70). MAIN RESULTS AND THE ROLE OF CHANCE The US testes volumes and caput diameters were reduced (P < 0.05) in NOA compared with OA and with normozoospermia, but the corpus values were not different. The caput diameter in the side submitted to biopsy was significantly reduced when germinal epithelium was absent (Sertoli cell only) (P < 0.05) and the lowest value of caput diameter was observed when the seminiferous epithelium and tubule lumen were absent (testicular hyalinosis). On the contrary, a total arrest of spermatogenesis at the first meiosis level, or a defect of spermiogenesis resulting in scattered elongated spermatids in each tubule, did not show a reduced diameter of caput epididymis compared with normozoospermia. The caput diameter did not show any difference between NOA patients with or without successful sperm retrieval at TESE. On the contrary testicular volume was significantly reduced in NOA patients with no sperm retrieval (P = 0.0037). The caput diameter was not correlated with the number of retrieved sperm, the serum level of follicle stimulating hormone, or with the percentage of tubules with elongated spermatids at histological analysis. LIMITATIONS, REASONS FOR CAUTION The aetiology of NOA was not included in the statistical analysis due to the low rate of cases with a specific aetiology for a testicular failure. Larger studies should exclude the possibility that besides testicular histology, aetiology of NOA might influence the diameter of caput epididymis. Moreover, whether a reduced diameter of caput epididymis is only a result of a testicular pathologic phenotype or whether it may underscore a primitive dysfunction influencing the number of ejaculated spermatozoa is not yet determined. WIDER IMPLICATIONS OF THE FINDINGS We reported that US diameter of the caput epididymis is reduced in cases of NOA but, in contrast with the testicular volume, it is independent of the completion of spermatogenesis and subsequent presence of spermatozoa in the epididymis. Therefore ultrasonographic determination of caput epididymis diameter is not predictive for positive sperm retrieval after TESE in cases of a primitive testicular failure. Our novel findings may help to define which reproducible parameters of scrotal US should be assessed in the work-up of male infertility. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the Ministero dell'Università e Ricerca (I) PRIN 2009. The authors declare no competing interest.