Review of Anatomy
Recall that the function of the vas deferens is to carry sperm from the testicle to the urethra. In the scrotum, the vas is located within the spermatic cord, which also contains the testicular artery and vein, and nerves.
Surrounding the vas itself is a fascial sheath, which contains small deferential arteries and veins that are important to identify during the procedure. These vessels are easily compromised during vasectomy, and may cause bleeding.
Important
It is essential to identify and control bleeding during the procedure to prevent post-procedure scrotal hematoma.
General Anatomy
Reproductive (male), By Unknown Illustrator [Public domain], via Wikimedia Commons.
Male_anatomy.png: alt.sex FAQ derivative work, By Tsaitgaist, CC-BY-SA-3.0, via Wikimedia Commons.
Spermatic Cord Anatomy: Cross Section
Gray1146 [Public domain], via Wikimedia Commons.