B-mode ultrasound and grey-scale analysis of the epididymis in boars, and the relationship to semen parameters

This study investigated the epididymis of mature boars (n=10) by means of B-mode ultrasound and grey-scale analysis (GSA) for echogenicity (EG) determination using an ultrasound unit HS 1500V, a linear transducer (frequencies 7.5-9.0 MHz), and standardized unit settings. All boars had their epididymal caput, corpus and cauda scanned six times before and after semen collection, respectively, at weekly intervals. Semen was subjected to spermatological examination including volume, total and forward motility, sperm abnormalities, as well as total sperm count and concentration. The caput and corpus both had a homogeneous fine echotexture. The cauda was homogeneous too but had a marbled echotexture. Echogenicity before and after semen collection was caput > corpus > cauda, respectively (p<0.001). Echogenicity was higher before than after semen collection for all parts of the epididymis, respectively (p<0.001). Echogenicity of the caput correlated slightly positively with the total sperm count pre-collection (r=0.301; p=0.020) and with ejaculate volume pre- and post-collection (r=0.302 vs 0.306; p=0.017 vs 0.019), and slightly negatively with sperm concentration post-collection (r= -0.275; p=0.034). No relationship was found for EG of the corpus and cauda for any of the ejaculate parameters. In conclusion, B-mode ultrasound and GSA proved feasible for imaging the epididymis in boars. Single relationships between EG and ejaculate parameters were found and deserve further investigation.