Overview of Deep Venous Thrombosis Ultrasound Evaluation
Deep vein thrombosis (DVT) is a fairly common health issue that can occur in the emergency room or in outpatient services. Clinically diagnosing DVT can be tricky because the typical symptoms – swelling, heat, redness, pain, and tenderness – only appear in around 23% to 50% of patients.
If a patient is showing signs of DVT, it’s crucial to correctly diagnose what’s happening, because if it isn’t treated in time, this condition can lead to bigger issues such as a lung embolism (a blockage in the lungs), superior vena cava syndrome (a blockage of the main vein to the heart), and other complications, including death.
However, the standard treatment for DVT, which involves using medicine to thin the blood (anticoagulation), also carries its own risks and can be expensive for the patient. A venogram, an X-ray of the veins, is the most accurate way to diagnose DVT, but it’s also an invasive procedure.
Instead, an ultrasound is often the best non-invasive method to diagnose DVT. Two main ways of using ultrasound for DVT diagnosis are increasingly evident. The traditional method involves having a fully trained ultrasound professional performing the procedure, which is then assessed by a radiologist.
More recent studies have shown that emergency and critical care physicians with appropriate training can perform bedside ultrasounds to look for DVT in the legs. These ultrasounds have shown high accuracy, with sensitivity and specificity rates around 95% and 96%, respectively. This means the test can correctly identify the presence or absence of DVT 95 to 96 times out of 100.
If more doctors are able to do these bedside ultrasounds, it could help to speed up treatment times in emergency departments for DVT. Another method known as “two-point compression”, where pressure is applied to two specific points on the leg, can be a quick way to check for DVT, particularly in patients who are less likely to have the condition. This method could be an even faster way to diagnose DVT at the bedside.
Anatomy and Physiology of Deep Venous Thrombosis Ultrasound Evaluation
The common femoral vein is a major vein in your leg that starts near the groin area and branches off twice. One of these branches is the greater saphenous vein and the other is the deep femoral vein. After these veins branch off, the common femoral vein changes its name to the superficial femoral vein, which is the primary vein in your lower leg. This vein then travels through a tunnel of muscles (adductor canal) and becomes the popliteal vein, located behind the knee. From here, it splits into three smaller veins: the anterior tibial, posterior tibial, and peroneal veins.
It’s important to note that the names of these veins can sometimes be confusing. Both the common femoral vein and superficial femoral vein are actually part of the deep vein system of the upper leg, even though the term “superficial” usually refers to something closer to the surface. On the other hand, the deep femoral vein, despite its name, is closer to the surface and is not considered part of the deep vein system. To avoid confusion, some people refer to the common femoral vein and superficial femoral vein together as the femoral vein. This naming issue is often addressed when describing medical conditions to avoid any misunderstanding, such as a blood clot in the deep femoral vein.
Moving on to the upper body, the vein system in the arm starts with the brachiocephalic vein, which then splits into the jugular vein and subclavian vein. The subclavian then further divides into the axillary vein and the cephalic vein, a large but superficial vein that runs along the length of the arm. The axillary vein then branches into two brachial veins, that run alongside a main artery in the arm. This vein then turns into another large but superficial vein, the basilic vein, running the length of the arm. Once the brachial veins get to the front of the elbow area, they split into multiple smaller veins, each one accompanying an artery in the upper side of the forearm.
Equipment used for Deep Venous Thrombosis Ultrasound Evaluation
A high-frequency linear probe is a perfect tool to use for an exam checking for deep vein thrombosis (DVT), a sort of blood clot. This is commonly a specialized 7.5 MHz tool used to better see small details. For folks who have a larger body type that surpasses the depth the high-frequency tool can reach, a curvilinear probe can be used instead. This is another type of tool used in ultrasound exams.
If the ultrasound machine has a pre-set function for DVT scanning, physicians should use that. If it is not present, the “venous” setting is the next best choice. “Vascular” and “small parts” are other alternatives to switch to if necessary.
Who is needed to perform Deep Venous Thrombosis Ultrasound Evaluation?
An ultrasound is a safe imaging test that can be used to find a deep vein thrombosis, or DVT, in your lower leg. DVT is a blood clot that forms inside a vein deep in your body. The ultrasound test is normally done by a doctor with special training in emergency medicine, an ultrasound technician, or another doctor who’s trained in using ultrasound machines.
However, if a DVT is suspected in your arm (upper extremity), the situation is different. We’re not quite sure if people other than ultrasound technicians are able to carry out the ultrasound test accurately. This is because there haven’t been enough studies done to find out.
Preparing for Deep Venous Thrombosis Ultrasound Evaluation
Examining the Lower Body
When a doctor needs to examine a patient’s lower body, they need to make sure the patient is as comfortable as possible and respect their privacy. The patient is usually asked to wear a medical gown and remove their pants and underwear. The doctor also uses a special cloth, known as a drape, to cover the patient’s body except for the area being examined. This is done to keep the patient from feeling embarrassed or uncomfortable.
To get a clear view of the lower body, the patient is typically asked to rotate their hip outward and slightly bend their knee. The bed can be tilted with the head end lower than the feet end to help the veins in the lower body swell up and become easier to see.
Examining the Upper Body
When checking the upper body, the patient is usually laying flat on their back with their head turned away from the arm that’s being looked at. The bed can also be tilted in a way that the feet end is lower than the head end. The patient’s arm should be straight and rolled inwards, sticking out from the body at a right angle. This positioning gives doctors the best view to assess the arm.
To get the best look at the forearm, the patient might be asked to sit up straight and keep their arm in a normal position, like they would when they’re not being examined.
How is Deep Venous Thrombosis Ultrasound Evaluation performed
If your doctor wants to see if there is a blood clot in your leg (also known as a deep vein thrombosis or DVT), they might use one of two methods.
In the “Classic Method,” the doctor will first put some gel on the upper part of your leg (the groin area). They will then slide a probe across your leg. The probe uses sound waves to create an image of the blood vessels in your leg. They watch for any areas where the vein does not get smaller when pressed on, as this could mean you have a clot. They also look at the color and speed of blood flow to see if anything is abnormal. They follow your vein down your leg, checking different points along the way. When they get to the back of your knee, the doctor might need you to change positions so they can see better. The doctor then checks another vein starting at the back of your knee and going down your lower leg.
In the “Two Point Technique,” the doctor only checks two main areas: where the large vein starts in your groin and behind your knee. Some doctors also check the vein in your upper leg. This method doesn’t check as many areas as the Classic method, but it can still be effective.
If the doctor wants to check for a clot in your arm (upper extremity DVT), they start by scanning the area underneath your collarbone. They then move to the area between your arm and torso (the armpit or axilla) and compress the veins there. The doctor will then scan down the length of your arm, checking the large vein (brachial vein) and the vein on the inner side of your arm (basilic vein). Finally, the doctor checks the veins in your lower arm and wrist, asking you to sit beside the bed to easily access these areas.
In all these methods, if a vein does not collapse when pressed on, it suggests there could be a clot there.
What Else Should I Know About Deep Venous Thrombosis Ultrasound Evaluation?
Identifying a Deep Vein Thrombosis (DVT), which is a blood clot in your veins, is crucial. The right treatment with blood thinners can prevent the clot from getting bigger or breaking loose, which can lead to serious health problems, such as a Pulmonary Embolism (PE), a blood clot in your lungs, or Superior Vena Cava Syndrome (SVCS), a blockage of blood flow in a large vein in your chest. It’s important to determine where the blood clot is found, such as above or below the knee or inside or outside the deep veins. This information helps health professionals decide on the best treatment and follow-up care.
Doctors often use a quick scan called an ultrasound to check for a DVT in the lower part of your body. This is because 90% to 95% of all DVTs occur in this area. Getting a clear picture of the clot quickly can help doctors make decisions faster and avoid unnecessary tests. This can make your visit to the emergency room smoother and shorter.
For example, when you’re considered at a low risk for DVT, a bedside assessment using an ultrasound can help avoid the need for a d-dimer test. A d-dimer test measures a substance in your blood that can indicate clotting, but it often leads to false positives, meaning that the test suggests you have a clot when you actually don’t. This can lead to additional tests. Also, an elective ultrasound isn’t always available, and it usually takes about an hour. Using an ultrasound at your bedside can reduce your time in the emergency room by about two hours, making the experience better for everyone.
