A 68-year-old man with carcinoma of the prostate presents with back pain. Imaging reveals osteoblastic metastases in the lumbar vertebrae without lung or liver involvement. Which anatomical route best explains this pattern of spread?
- A Lymphatic spread to para-aortic nodes then retrograde to bone
- B The prostatic venous plexus communicating with the internal vertebral venous plexus ✓
- C Arterial embolisation via the median sacral artery
- D Direct extension through the sacroiliac joints
Correct answer: B. The prostatic venous plexus communicating with the internal vertebral venous plexus
Explanation
The prostatic venous plexus, lying between the prostatic capsule and the endopelvic fascia, drains into the internal iliac veins and connects valvelessly with the internal vertebral (Batson) venous plexus. Raised intra-abdominal pressure drives blood retrogradely into the spinal veins, seeding the lumbar spine and pelvis with osteoblastic deposits. This valveless connection is the classic explanation examined for early vertebral metastasis.
Reference: Gray's Anatomy for Students, 4th ed.
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