Morphological changes in the canine epididymis during recovery after 5-month treatment with a deslorelin implant

Administration of slow-release GnRH agonist implants (SRI) is a well-established alternative to surgical castration in small animal medicine. Whereas clinical-andrological, endocrine and testicular histological changes have been investigated in depth, research on epididymal changes during treatment and recovery is largely miss-ing. To gain further insights, healthy dogs were treated with a deslo-relin SRI over 5 months, the SRI was removed at 5 months and 4–5 dogs were castrated at implant removal (week, W 0) or 2, 4, 6 or 10 weeks after SRI removal. Testes of untreated healthy male dogs served as controls (CG). Besides testes, epididymides were collected and samples taken from the head, corpus and tail region. Slides from Bouin-fixed, paraffin-embedded tissues were haematoxylin-eosin stained and histologically assessed. In each dog and region, epithe-lial height, presence of spermatozoa, cilial height, thickness of the muscle layer and presence of connective tissue were evaluated with a semiquantitative scoring by a blinded evaluator. GraphPad Prism was used for statistics. Epithelial (p < .01) and cilial height (p < .05), presence of spermatozoa (p < .05) and presence of connective tis-sue (p < .05) differed significantly between samples in all epididymal regions (Kruskal–Wallis) with lower epithelium and cilia, as well as less spermatozoa, but more connective tissue being present in early samples (W0 and/or W2) compared to later ones. The present re-sults clearly show that downregulation by an SRI induces not only significant testicular changes but also affects epididymal morphol-ogy indicating the need for further studies.