“…Many studies have been published on semen parameters in patients with UDT. Such studies are not always easy to compare because of several reasons; (i) different therapeutic strategies, (ii) variation in reporting the results (mean values, median values or percentage normal/abnormal), (iii) the WHO-reference values for semen analysis have changed over time, (iv) uncertainty whether groups contain only congenital UDT or also acquired UDT, (v) groups may contain unilateral or bilateral UDT or a combination of both, (vi) unclear about the exclusion of retractile testis (Canavese, 2009;Cortes & Thorup, 1991;Cortes, 1996;Coughlin, 1999;Engeler, 2000;Gracia, 2000;Lee & Coughlin, 2001;Taskinen, 1996;Vinardi, 2001). In this study, men with retractile testis or acquired UDT were excluded and this might be an explanation for our low sperm concentration in comparison with the literature.…”