Amanda has taught high school science for over 10 years. They have a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. They also are certified in secondary special education, biology, and physics in Massachusetts.
What Is Deep Vein Thrombosis?
You're walking to work, but you come across a blocked-off sidewalk. All foot traffic is diverted onto a small, unpaved pathway where bikes and pedestrians and locked in a gridlock. You're nearly late to work because of this backed-up traffic.
Something similar can happen in your body. In a condition called deep vein thrombosis, blood clots form in the deep veins of the body, usually the legs. Blood backs up and can damage both the clogged veins and veins nearby. Sometimes, the damage can become permanent, even after the clot is removed. Let's look at the tests needed to diagnose deep vein thrombosis.
John has been traveling from Boston to Shanghai for work, and he is often on flights lasting ten hours or more. His doctor warned him about a condition called deep vein thrombosis. Inactivity can cause the blood to clot more easily, so long flights can be a risk factor. After one international flight, he noticed some swelling, redness and pain in his leg. Thinking it could be a blood clot, he went to the doctor.
First, the doctor did a physical exam. He asked John about his symptoms and examined his leg and noticed the redness and swelling. John's doctor decided to do some additional tests involving blood work and scans.
The doctor explained that when there is a blood clot in the body, your body will try to dissolve it by making natural clot busting factors. When the blood clot is broken down it releases a small piece of protein called a D-dimer. A D-dimer test detects the presence of this molecule and can indicate that a blood clot is present, but can't help locate where. If the test is positive, the doctor will have to do some scans to find where the clot is located. D-dimers are a pretty good indicator of deep vein thrombosis, but more information is needed about where the clot is to make a final diagnosis.
John's test was positive for D-dimers, so the next step is to locate the clot with an ultrasound, the same type of imaging used to look at developing fetuses during pregnancy. Ultrasound is often the first step because it doesn't require exposing the patient to radiation.
In an ultrasound, a wand, or transducer, emits sound waves that hit solid masses inside the body and bounce back to the machine, which creates a picture. If this image reveals the location of the clot, doctors can accurately diagnose. If the clot is not visible, additional tests may be needed.
One additional test, an MRI scan, gives a better picture of the veins than an ultrasound and can be used to visualize clots through a cast, which is helpful for patients who may experience clots due to surgery. In an MRI, a tube like machine emits radio waves, long waves that cause hydrogen ions inside cells to line up. When the radio waves stop, the hydrogen ions return to their original location. When they do this, they emit energy that the MRI machine can detect. The hydrogen ions give off different signals depending on how the blood is flowing. So, if the blood behind a clot is backed up, the MRI will be able to detect it.
Venography uses X-rays to visualize the veins and identify clots. Normally, the X-rays travel through soft tissues, like muscle and blood vessels, but doesn't go through bone.
However, during a venography a contrast dye, usually containing iodine, is injected into the patient's veins to make them show up on an X-ray. The iodine absorbs some of the X-rays, preventing them from reaching the film. This allows any tissue containing the iodine to show up on the film. However, most doctors will use an ultrasound first, because the dye injection causes an allergic reaction in some patients, and X-rays contain small amounts of radiation.
Computed tomography (CT) scans are similar to X-rays and also use a contrast dye to make veins visible. The difference is that in a CT scan, the person is inserted into a tube where a device emitting X-rays is rotated around them. The film is digital and pictures are sent to a computer, which processes the information into slices of the soft tissue. It's as if the body is a sandwich, and this tool lets you look at all the layers inside without opening it up. However, CT scans are used for many conditions and are often in high demand. They won't usually be used for deep vein thrombosis alone.
Deep vein thrombosis is a condition where blood clots form in the deep veins, usually the extremities. To diagnose deep vein thrombosis, a doctor will first do a physical examination and then a D-dimer test to look for evidence of blood clots being broken down. To locate the blood clot, doctors use an ultrasound, which uses sound waves to detect solid masses in the veins. They also may use an MRI to detect changes in blood flow, a venography to visualize the veins, or a CT scan to get a three dimensional picture of the blood vessels. A positive test for the D-dimer test indicates a blood clot and the imaging shows where the blood clot is located, providing doctors with a final diagnosis.
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.
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