The bilateral persistent sciatic vein: a rare and clinically meaningful lower limb variant.

Background: The lower limb venous system, a subject of extensive study due to its high clinical significance on deep vein thrombosis, presents a rare, intriguing, symmetrical variant in this dissection report.

Case Report: We present the uncommon and clinically meaningful bilateral persistent sciatic vein (PSV) variant. The developmental variant was symmetrically detected during a dissection of an 81-year-old female donated cadaver. The symmetrical PSV originated from the popliteal vein (PV, merging of the anterior and posterior tibial vein), coursing through the abductor magnus muscle and draining into the common femoral vein after joining the femoral and greater saphenous vein. The enlarged PSV was the developmental variant at the saphenopopliteal junction, while the "typical" PV was hypoplastic as a regressed vessel.

Conclusion: The typical PV was hypoplastic; the enlarged PSV was the lower limb's primitive axial vein that acted as the central (main) drainage vessel. After a thorough literature search, the PSV variant was recorded as having a low prevalence in the general population. The current dissection finding is relatively rare due to its symmetric occurrence. The rare variant is related to Klippel-Trenaunay Syndrome, a congenital vascular malformation. Clinicians must distinguish the primitive axial vein (PSV) from the transformed axial vein (pathology) to avoid complications and iatrogenic injury.