The caliber of the human long saphenous vein and its congenital variations.

The purpose of the present study is to evaluate the caliber of the normal human long saphenous vein (LSV) in order to verify the occurrence of congenital narrowings. The LSV morphology was evaluated by the dissection of 32 cadaveric limbs, and by ultrasonography of 102 healthy living subjects. The LSV caliber was constant in most of the limbs, showing only a mild and progressive increase from the ankle to the groin. Furthermore, great individual variation in LSV caliber was found. A segmental narrowing of the LSV was present in 39.8% of limbs. The narrow segment was visible with the naked eye during dissection or by ultrasonography in 22.4% of cases (LSV hypoplasia). In the remaining 17.4% the caliber was so reduced that it could only be detected microscopically (LSV aplasia). In relation to the narrow segments, the main ascending flow was shunted in a collateral vein running within the superficial hypodermis. The narrow segments of the LSV had a weaker and less muscular wall than did those of normal caliber. Hypoplasia and aplasia of the LSV are probably due to segmental failure in the development of the vessel, and represent a risk factor for varicosis. In fact, the ascending flow is shunted from the LSV in a collateral vein that runs in the yielding superficial fatty layer of the hypodermis. Furthermore, the high incidence of LSV segmental hypoplasia and aplasia has also to be considered whenever this vein is used as an arterial graft, because of the marked anatomical remodelling.