Ultrasound of superficial veins of the lower extremity

Ultrasound Dopplerography of Superficial Veins

Examination for venous insufficiency

Although venous valves can be visualized on ultrasound, the diagnosis of venous insufficiency is based on indirect signs. As proximal pressure increases when the patient performs the Valsalva maneuver or manual compression, the physician attempts to register a distal reflux signal, which is normally prevented by the venous valves. Complete saphenous varices begin with insufficiency at the level of the terminal valve and progress to distal levels over time. As a result, the blood filling the superficial weakened veins comes from the deep venous system. When proximal pressure increases (e.g., during the Valsalva maneuver), the deep venous valves close if the deep venous system is intact, resulting in reflux only between the superficial vein and the nearest proximal deep venous valve. This segment may be quite large in the case of the great saphenous vein, but the popliteal vein has so many valves that the reflux volume is very small. As a result, varicosities in the small saphenous vein are much more difficult to detect than in the great saphenous vein.

The most proximal incompetent valve is the proximal reflux point or the proximal limit of venous insufficiency. The first competent valve of a varicose vein is the distal reflux point. The proximal and distal reflux points allow classification of saphenous vein varices. The proximal reflux point usually consists of a dysfunctional saphenous-femoral valve (complete saphenous varices. The level of the distal reflux point determines the severity and location of the varices according to the Hach classification: grade I - proximal thigh; grade II - distal thigh; grade III - proximal leg; grade IV - distal leg. A similar three-stage classification is used for the small saphenous vein. If the proximal reflux point is located distal to the terminal valve, the saphenous varices are classified as incomplete.

Ultrasound anatomy

The great saphenous vein arises from the medial border of the foot, ascends anterior to the medial malleolus, and joins the femoral vein approximately 3 cm below the inguinal ligament. There are variations in which the great saphenous vein joins the superficial epigastric vein (abnormal proximal termination) or the femoral vein below the venous confluence (abnormal distal termination).

The small saphenous vein begins at the lateral border of the foot, ascends behind the medial malleolus and empties into the popliteal vein 3-8 cm above the knee joint line. The terminal part of the small saphenous vein is located subfascially and is inaccessible for examination. Usually, the great and small saphenous veins narrow towards the periphery (the "telescope" sign). Tubular, unnarrowed vessels with direct blood flow are a sign of extrafascial collateralization in deep vein thrombosis, while a tubular vessel with reverse blood flow indicates venous insufficiency. A significant decrease in blood flow velocity in incompetent veins can cause the presence of spontaneous intraluminal echoes. These echoes disappear when pressing with the transducer.

Research methodology

The patient is examined in a standard position with relaxed legs. Alternatively, the leg can be flexed and lowered over the edge of the table to examine for varicose veins below the knee. Once the terminal sections of the saphenous veins have been identified, proximal pressure on the transducer is increased to assess the functional state of the valves. The test is repeated at several levels to determine the distal border of venous insufficiency. Venous compression is performed proximally during the Valsalva maneuver to determine whether there is insufficiency of the saphenous veins themselves or whether there are additional aspects (insufficiency of the lateral branches and perforating veins). In patients with incomplete varicose veins of the saphenous veins, the proximal border of venous insufficiency is determined in this way. Insufficiency of the perforating veins can be visualized using ultrasound Dopplerography. There is no need for bandaging, as with continuous-wave Dopplerography. Scanning the entire limb to look for incompetent perforating veins is impractical; the examination should be limited to clinically suspicious areas (eg, area of swelling, typical skin changes).