A 70-year-old man with advanced carcinoma of the prostate develops low back pain. Imaging shows sclerotic metastases in the lumbar vertebrae without lung or liver involvement. Which anatomical pathway explains this pattern of spread?
- A Direct extension along the sacrotuberous ligament to the sacrum
- B Retrograde flow through the prostatic venous plexus communicating with the internal vertebral venous plexus (Batson's plexus) ✓
- C Lymphatic spread via the external iliac chain to the retrocrural nodes
- D Haematogenous spread through the systemic arterial circulation seeding the vertebral bodies
Correct answer: B. Retrograde flow through the prostatic venous plexus communicating with the internal vertebral venous plexus (Batson's plexus)
Explanation
The prostatic venous plexus lies between the prostatic capsule and the endopelvic fascia and drains into the internal iliac veins, but it also anastomoses freely with the valveless internal vertebral venous plexus. Raised intra-abdominal pressure can drive retrograde flow through these valveless channels, carrying tumour cells directly to the lumbar vertebrae. Arterial haematogenous spread would reach the lungs first, which kills option D.
Reference: Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd ed.
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Written and medically reviewed by the StethoPrep medical team.