Ultrasound of the lower extremities

Deep veins of the lower limb accompany the same-named arteries. Usually veins below the knee joint go in pairs. To demonstrate the front tibial veins, place the sensor on the palpable anterior tibial muscle on the side of the anterior edge of the tibia. The anterior tibial vein is located posteriorly from the extensor muscles and slightly anterior to the interosseous membrane. Inexperienced doctors often scan too deeply. The interosseous edges of the tibial and fibular bones show the level of the interosseous membrane, which can be directly visualized by ultrasound.

The posterior tibial and peroneal veins are located in the region of flexors between the triceps and deep flexors. For guidance, bony landmarks are used: when the leg is held in a neutral position, the posterior surface of the tibia is anterior to the posterior surface of the fibula. The posterior tibial veins are located at the center of the posterior surface of the tibia, while the peroneal veins are very close to the fibula.

The reference point for the popliteal vein is the artery of the same name, which runs anterior to it. The vein is easy to find because of its large caliber and surface location. Even a slight depression of the sensor often allows the vein to be completely compressed, and its image disappears. Popliteal vein in 20% of cases is a pair and in 2% is triple. The femoral vein lies behind the artery in the adductor channel, being medial to the artery at a more proximal level. The iliac vein goes posteriorly and medially from the artery of the same name. The deep femoral vein runs into the superficial vein at a distance of 4-12 cm below the inguinal ligament. It goes anterior to the artery of the same name. The superficial femoral vein in about 20% is a pair, and three or more veins are found in 14% of cases.

Examination with thrombosis

The most accessible technique of ultrasound in the diagnosis of deep vein thrombosis of the lower extremities is a test with compression that can be performed from the groin area to the ankles. The color mode is used only for guidance, since the vessels are easier to visualize. If the quality of the B-mode is good, you do not need to use the color mode for the sample with compression. The key criterion is not the "extrusion of color", but the complete compressibility of the vascular lumen. If the image in the B-mode is of poor quality, you should use the color mode and, if necessary, combine it with the distal compression.

The most elegant test with compression is the swinging motion of the hand holding the sensor. Increased blood flow allows the doctor to identify the vein and make sure that it is at least partially passable. The hand then moves forward by pressing the sensor. When examining without compression, the blood flow in them is not determined. With distal compression there is an acceleration of blood flow. Then the sensor is fully compressed. It is only possible to accurately evaluate the venous segment, which is subjected to compression. Thus, several transverse images should be obtained along the full length of each of the veins of the lower limb (common femoral, superficial femoral, deep femoral, popliteal, tibial, tibial and fibular veins) when applying a variable compression.

In most cases, iliac veins are not subject to compression because of the lack of a dense underlying tissue, so the evaluation is done in color.

[1], [2], [3], [4], [5], [6], [7], [8]

Methods of examination

For duplex scanning of the veins of the lower extremity, the patient is located on the back, the upper end of the body is slightly elevated. Start the study from the inguinal area with a linear 4-7 MHz sensor. Trace the femoral vein distally from the epicondyle of the thigh with variable compression. Note also the course of the deep femoral vein. Get down on the extremities and scan the front tibial veins, then turn the patient over to the abdomen. For easy bending of the knee, a small roller is placed. Remove the popliteal vein in a cross section. First track the vessel proximally, then perform variable compression (often the distal section of the lead channel is better visualized from the rear access than from the front). Further trace the vessels distally and separately evaluate the posterior peroneal and tibial veins.

Be careful when examining the proximal sections of the peroneal veins. Because of their physiological expansion and normal tension of the skin above the fibula, use a strong and often painful depression to compress these veins. The conclusion of a specialist depends on the data obtained at this point and on the clinical symptoms. Make a conclusion either by examining the common femoral vein while the patient performs the Valsalva test, or according to the color scan of the iliac veins using a 4-7 MHz convection sensor.

If you can not adequately assess the leg veins using this standard protocol, try bending the leg in the knee joint and lowering the relaxed lower leg part across the edge of the table or bed. Hold the shin with your left hand, and scan the right one. Increased hydrostatic pressure will lead to better filling of veins, which will allow them to be better identified. On the other hand, color scanning deteriorates due to a slowing of blood flow and the need for more force to compress the veins than in a lying position.