How Is Deep Vein Thrombosis Diagnosed?

Your doctor will obtain a medical history and examine you to determine if you have deep vein thrombosis.

Commonly Used Tests

• Duplex ultrasound is the most commonly used test to diagnose deep vein clots. It uses sound waves to evaluate the flow of blood in your veins. A gel is put on the skin of the leg. A handheld device is placed on the leg and passed back and forth over the affected area. This device sends sound waves from the leg to an ultrasound machine. A computer then turns the sound waves into a picture. The picture is displayed on a TV screen where your doctor can see the blood flow in your leg.
  

• Venography may be performed if the duplex ultrasound does not provide a clear diagnosis. A venogram is an x ray used to examine veins. A dye is injected into a vein and then an x ray is taken of the leg. The dye makes the vein visible on the x ray. If the blood flow in the vein is slowed, it will show on the x ray.
  

Less Frequently Used Tests

• Magnetic resonance imaging (MRI) shows pictures of organs and structures inside the body. MRI uses radio waves to make the image. In many cases, MRI can provide information that would not show up on an x ray. This test is being used more frequently to diagnose deep vein thrombosis.
  

• Computed tomography scan is a special type of x ray that can provide pictures of structures inside the body. This test is rarely used to diagnose deep vein thrombosis.
  

If an inherited blood clotting disorder is suspected, tests may be run for it. The presence of an inherited clotting disorder is suggested by:

• Repeated blood clots that can’t be linked to any other cause
• Development of a blood clot in a vein at an unusual location, such as a vein in the liver, kidney, or brainz