Anatomical Study On The Junction Of Human Testis And Epididymis And Its Clinical Potential

Background&Objective:The incidence rate of male infertility is gradually increasing.Azoospermia is the key point of clinical practice which can be classified as obstructive azoospermia and non-obstructive azoospermia,according to the presence or absence of obstruction.Obstructive azoospermia,characterized by normal spermatogenesis,may be classified as intratesticular obstruction,epididymal obstruction,vas deferens obstruction and ejaculatory duct obstruction.Currently,for azoospermia patients with normal neutral alpha glucosidase and normal spermatogenic function indicated by testicular biopsy,it can be diagnosed with obstruction above the level of the distal epididymis,but there is still no consensus on whether the obstruction is within the testis or at the testicle-epididymis junction.Non-obstructive azoospermia,which means primary or secondary testicular failure,can be divided into Sertoli cell only syndrome,spermatogenesis arrest and severe hypospermatogenesis according to the result of testis biopsy.For some patients with different types of spermatogenesis disorders confirmed by testicular histopathology accompanied by neutral alpha glucosidase decline,current examination procedures cannot rule out whether they are combined with obstruction above the distal end of the epididymis after excluding obstruction of epididymis and vas deferens.In addition,for patients with severe oligospermia(including cryptozoospermia)accompanied with neutral alpha glucosidase decline,whether obstruction factors are involved in the pathogenic process and lead to little sperm in semen remains to be further confirmed.Therefore,it is great clinical value to define the duct structure above the epididymis level,especially the structure of the "rete testis",to analyze the possible pathogenic factors and explore the possible therapeutic means.At the same time,some studies have shown that the human epididymis is different from that of other mammals,and the results obtained in animal experiments cannot be directly applied to humans.Therefore,it is necessary to correctly distinguish the anatomical structure and biological function of human epididymis.So the purpose of this study is to investigate the morphological structure and biological function of the epididymis-testis junction of human testis and thus to provides a new approach for diagnosis of the possible obstructive position above epididymal level.Methods:9 adult male scrotum and its contents specimen(7 frozen and 2 fresh)are dissected with great care to conserve organ integrity so that testis and its appendages can be visualized.By retrograde infusion through vas deferens,ink perfusion and histologic section,cast specimens and micro CT image reconstruction are completed.Results:An ink-no ink boundary could be observed in epididymis.Bullae retis which is the portion of the rete testis outside the testis did not migrate directly to the caput epididymis after entering the epididymis.And the ink could not pass smoothly through bullae retis after retrograde infusion.The boundary between ink and no ink lied in the epididymal tube,distributed along the longitudinal sections.Conical bulge caused by the obstruction could be observed in cast specimens and micro CT image reconstruction.Conclusions:This study showed that bullae retis was not turning directly into caput epididymis through rete testis,and it might be the distinguishing mark of caput epididymis and corpora epididymis.And there was an anti-reflux mechanism between the caput epididymis and corpus epididymis,which might be concerned with the continuation of bullae retis in epididymis or longitudinal sections.