(713) Male Factor Infertility Specific Causes: Prevalence Study of a Severe Male Factor Cohort

Introduction Male infertility is a heterogeneous condition characterized by multiple underlying etiologies. In many cases, the etiology remains unidentified, leading to the diagnosis of idiopathic infertility. In other cases, specific causes of male infertility can be identified and potentially treated. The knowledge of real-life prevalence of male infertility specific causes can help health providers with pragmatic diagnostic algorithms and resource allocation in the management of this condition. Objective To determine the prevalence of non-genetic male infertility etiologies in chilean men consulting at a assisted reproduction clinic andrology unit with a severe male factor (azoospermia and severe oligozoospermia) Methods Retrospective study, of 231 infertile men with severe oligozoospermia (< 5 mill/mL) and azoospermia with palpable vas deferens, consulting at a tertiary andrological unit, between 2018 and 2025. Patients were stratified by sperm concentration: Azoospermia, <2 million/mL and 2-5 million/mL. All patients were classified by etiology as: clinical varicocele, history of cryptorchidism, endocrine disorder (hypogonadotrophic hypogonadism), syndromic condition and inflammatory testicular disorder. If no specific condition was present, patients were classified as idiopathic Results 231 men were studied. Male infertility related conditions prevalence had different distributions depending on sperm concentration groups. Overall, idiopathic infertility was the most common diagnosis 62.3% (N=144), followed by varicocele 22.9% (N= 53), cryptorchidism 8.7% (N=20), endocrine disorder 3.5% (N=8), genetic syndrome 2.2% (N=5), and inflammatory testicular pathology 0.4% (N=1). Distribution by concentration revealed that in azoospermic patients (N=125): Idiopathic etiology predominated 69.6% (N=87), followed by varicocele 14.4% (N=18), cryptorchidism 9.6% (N=12), endocrine disorder 4.8% (N=6), severe genetic disease 0.8% (N=1), and inflammatory testicular pathology 0.8% (N=1). In Oligozoospermic <2 million/mL (N=67): Idiopathic cases comprised 35 patients (52.2%), with varicocele as the leading identifiable etiology 31.3% (N=21), followed by cryptorchidism 9% (N=6), syndromic disorder 6% (N=4), and endocrine disorder 1.5% (N=1). In the group of 2-5 million/mL (N=39): Varicocele was the most prevalent condition 35.9% (N=14), with idiopathic cases accounting for 56.4% (N=22), cryptorchidism 5.1% (N=2), and endocrine disorder 2.6% (N=1). Conclusions Idiopathic infertility remains the most prevalent diagnostic group among men presenting with a male factor infertility, irrespective of sperm concentration severity. This etiology group accounted for 62.3% of all men studied. This underscores the ongoing diagnostic challenges in male reproductive medicine. A clear concentration-dependent gradient was observed in varicocele prevalence, increasing from 14.4% in azoospermia to 35.9% in the 2-5 million/mL group. Cryptorchidism showed relatively stable prevalence across all concentration ranges (5.1-9.6%), indicating its consistent role as a risk factor for severe male factor infertility. Endocrine disorders (hypogonadotrophic hypogonadism), predominantly observed in azoospermic patients (4,8%) represents a critical treatable cause requiring systematic hormonal evaluation. Disclosure No