Epididymal obstruction results in isolated sperm heads in post-vasectomy rats

The aim of this study was to determine if, following vasectomy, epididymal obstruction resulted in changes in vasal stump fluid using a rat vasectomy model. One hundred and twenty-two mature male rats underwent bilateral surgical vasectomy and subsequent unilateral epididymal obstruction. Animals were randomly assigned to one of the five cohorts, which determined the time to kill and vasal fluid assessment. Numbers of whole sperm and sperm heads were compared between the obstructed and non-obstructed sides. Parametric analysis of microscopic vasal fluid findings was performed using a paired t-test. Whole sperm and sperm heads were detected bilaterally among the initial five cohorts. On the obstructed epididymis side, percentage of whole sperm dropped from 36.9% to less than 1% and sperm heads increased from 63.2 to 99.7% at 12 weeks post-obstruction (p < 0.05 at each time interval). On the unobstructed side, percentage of whole sperm rose from 66.3 to 89.5% and sperm heads dropped from 33.7 to 10.5% (p < 0.05 at each time interval). At 12 weeks, the difference between the obstructed and non-obstructed sides for both percentage and quantity of whole sperm and heads was significant with a p value of <0.001. In this rat model, following vasectomy and subsequent epididymal obstruction, testicular vasal stump fluid will contain progressively diminishing numbers of whole sperm and increases in the percentage and absolute numbers of sperm heads.