A blood clot of the leg is diagnosed with ultrasound. The ultrasound is performed by a specially trained technologist and interpreted by a radiology doctor. The ultrasound uses sound waves to form an image of the body. There is no radiation. The ultrasound of the leg will usually be done from the groin region to the calf.
The test focuses on the deep veins of the leg
The test looks at the deep veins of the leg. These veins are called the common femoral, superficial femoral, popliteal, peroneal, anterior and posterior tibial veins. Some exams also include some of the other superficial and deeper veins.
The ultrasound technologist will use ultrasound to look at each vein. They will compress the veins throughout the legs. A vein which compresses completely usually does not have a clot. The compression of the veins is usually not painful.
The technologist will also show flow in the veins. They may squeeze your leg to show blood flow augmentation. This will make the blood flow increase in the vein. This also supports there being no clot. A vein which is clotted will not show increased flow in response to squeezing the leg.
Why is it important to promptly diagnose a blood clot in the leg?
A clot in these deep veins is dangerous because it can travel to the lungs. This can cause symptoms like chest pain, shortness of breath and even death in some cases. A blood clot in the deep veins of the leg can be accompanied by pain in the leg. A clot to the lungs can be further evaluated with a CT.
An ultrasound of the leg for clot will also look for a cyst behind the knee called a baker’s cyst. This can be symptomatic and cause leg pain. We can see other fluid collections or bleeding as well. We also sometimes see enlarged lymph nodes in the groin. These lymph nodes can be reactive from an infection or related to cancer.
We can identify chronic blood clots
An ultrasound of the leg for clot can also identify clots which have been present for a long time. These often have a more chronic look to them. There can be thickening of the walls of the veins from chronic clots. The vessels may be smaller and have reduced flow and compression from chronic clots.
Ultrasound of the leg veins is the best test to diagnose a blood clot. In addition to looking at the vein with ultrasound, the technologist will also compress the veins throughout the leg. They will squeeze your leg as an additional maneuver to evaluate for clot.
They will also focus on the area where it hurts you. Sometimes superficial veins with clot under the skin can be a source of pain. This can also be diagnosed with a leg ultrasound. They may see a site of bleeding, fluid or enlarged lymph nodes.