Previous studies concerning ultrasound evaluation of the seminal vesicles (SV) were performed on a limited series of subjects, and considered few parameters, often only before ejaculation and without assessing the patients' sexual abstinence. The aim of this study was to evaluate the volume and the emptying characteristics of the SV and their possible correlations with scrotal and transrectal ultrasound features.
The SV of 368 men seeking medical care for couple infertility were evaluated by ultrasound. All patients underwent, during the same ultrasound session, scrotal and transrectal evaluation, before and after ejaculation, and the ejaculate was subjected to semen analysis. A new parameter, SV ejection fraction, calculated as: [(SV volume before ejaculation - SV volume after ejaculation)/SV volume before ejaculation] × 100, was evaluated.
After adjusting for sexual abstinence and age, both pre-ejaculatory SV volume and SV ejection fraction were positively associated with ejaculate volume. As assessed by receiver operating characteristic curve, a cut-off for SV ejection fraction of 21.6% discriminates subjects with normal ejaculate volume (≥1.5 ml) and pH (≥7.2 ml) with both sensitivity and specificity equal to 75%. Subjects with SV ejection fraction of <21.6% more often had a higher post-ejaculatory SV volume and ejaculatory duct abnormalities. Furthermore, a higher post-ejaculatory SV volume was associated with a higher prostate volume and SV abnormalities. Higher epididymal and deferential diameters were also detected in subjects with a higher post-ejaculatory SV volume or reduced SV ejection fraction. No association between SV and testis ultrasound features or sperm parameters was observed. Associations with SV ejection fraction were confirmed in nested 1:1 case-control analysis.
The SV contribute significantly to the ejaculate volume. A new parameter, SV ejection fraction, could be useful in assessing SV emptying. A SV ejection fraction of <21.6% was associated with prostate-vesicular and epididymal ultrasound abnormalities.