Correlation between epididymal length and fertilization rate in men with congenital absence of the vas deferens

Abstract

To investigate whether the variable length of the epididymides in men with congenital absence of the vas deferens might have a correlation with IVF and pregnancy rate results. Microsurgical retrieval of epididymal sperm from men with congenital absence of the vas deferens and their use for IVF. Center for Reproductive Health, University of California, Irvine, California. One hundred eight men with confirmed diagnosis of congenital absence of the vas deferens enrolled in the microsurgical epididymal sperm aspiration and IVF program. Measurement in centimeters of the epididymal length at the time of the sperm aspiration procedure. Rates of fertilization and pregnancy according to the epididymal length. Three groups were identified: group I (n = 29), epididymal length between 0.5 and 1.9 cm; group II (n = 66), length between 2.0 and 4.0 cm; and group III (n = 13), length in excess of 4.0 cm. Although the aspiration site was the proximal caput for each case, patients of group III had the highest fertilization and pregnancy rate (24% and 43%, respectively). Patients with the shortest epididymis (group I) had the worst IVF outcome (fertilization rate 7% and pregnancy rate 7%) whereas in group II the fertilization rate was 13% and the pregnancy rate was 18%. This study demonstrates that epididymal sperm from men with congenital absence of the vas deferens having a longer epididymis have a better IVF rate. A long epididymis can allow [1] the arrival of more frequent waves of fresh sperm whereas in a short epididymis the system is completely congested and occupied by old and senescent sperm, [2] less obstructive damages, and [3] a back flow of biochemical factors produced in the more distal segments that could ultimately enhance the fertilization capacity of proximal epididymal sperm.