The prostatic venous plexus drains into the internal iliac vein which in turn connects with the vertebral venous plexus; this is thought to be the route of bone metastasis of prostate cancer.[2]
^"Male Genitals - Prostate Neoplasms". Pathology study images. University of Virginia School of Medicine. Archived from the original on 2011-07-20. Retrieved 2011-04-28. There are many connections between the prostatic venous plexus and the vertebral veins. The veins forming the prostatic plexus do not contain valves and it is thought that straining to urinate causes prostatic venous blood to flow in a reverse direction and enter the vertebral veins carrying malignant cells to the vertebral column.
External links
Anatomy photo:44:05-0103 at the SUNY Downstate Medical Center - "The Male Pelvis: The Prostate Gland"