Detecting Blood Clots: Hospital Techniques And Procedures

Blood clots can be life-threatening depending on their location and severity, and they can form almost anywhere in the veins or arteries. To diagnose blood clots, doctors will usually begin by obtaining a patient's medical history and performing a physical examination. There are several tests that can be used to check for blood clots, including ultrasounds, CT scans, MRIs, and X-rays. Treatment options include medication, catheter-directed thrombolysis, surgery, and inferior vena cava (IVC) filter placement.

Physical examination

For deep vein thrombosis (DVT), which typically occurs in the legs, symptoms can include swelling, tenderness, or changes in skin colour. The affected area may be warmer than usual, and the patient may experience pain or discomfort similar to a pulled muscle. DVT can also develop in the pelvis, abdomen, or arms, causing abdominal pain, flank pain, severe headaches, or seizures. Arterial clots, on the other hand, produce symptoms quickly as they cut off oxygen to organs.

A physical exam can diagnose superficial venous thrombosis, which occurs in veins close to the skin's surface. However, an ultrasound is required to diagnose DVT. This non-invasive test uses sound waves to visualise blood flow and detect blockages or clots in the deep veins. If ultrasound results are inconclusive, more invasive tests such as venography or MRI may be necessary.

In cases of suspected pulmonary embolism (PE), where a clot travels to the lungs, doctors may perform a CT angiography scan of the chest. They may also request a D-dimer blood test, which measures a substance produced when a clot breaks up. If the D-dimer test is negative, it is unlikely that the patient has a blood clot. For a definitive diagnosis of PE, a pulmonary angiogram is often performed, involving the injection of contrast dye and X-rays to monitor blood flow in the lungs.

Ultrasound

During an ultrasound, the patient wears a hospital gown and is covered by a sheet, with only the leg being evaluated exposed. The head of the bed is typically positioned at a 30- to 45-degree angle to direct more blood flow to the legs. Ultrasound gel is applied to the patient's leg, forming a bond between the skin and the probe, which allows sound waves to reach the blood vessels under the skin. The probe is moved slowly and gently across the leg, and the waves form images that appear on a nearby computer screen. If a DVT is identified, a still picture can be taken.

The accuracy of ultrasound in detecting DVT varies depending on the location of the clot. Ultrasound finds about 95% of DVTs in the large veins above the knee, while it identifies only 60-70% of DVTs in calf veins. Ultrasound is also used to detect clots in the neck that may have travelled to the brain, as well as in the pelvis, abdomen, and chest, although MR venography is considered superior for imaging these areas.

If an ultrasound cannot provide a definitive diagnosis, other screenings may be necessary, such as a CT scan, MRI, or venography.

D-dimer blood test

A D-dimer blood test is a simple test that can help healthcare providers determine if a patient may have a blood clotting condition. D-dimer is a protein fragment that is released when a blood clot dissolves. It is normally undetectable or found at very low levels in the blood, unless the body is forming and breaking down significant blood clots.

A healthcare professional will take a blood sample from a vein in the patient's arm, using a small needle. The procedure usually takes less than five minutes, and there is very little risk involved. The patient may feel a slight sting when the needle is inserted or removed, and slight pain or bruising may occur at the spot where the needle was inserted. However, most symptoms disappear quickly.

If the D-dimer test result is negative, it means the patient probably does not have a blood clot. A positive result, on the other hand, indicates that the patient may have a blood clotting condition, but it does not guarantee it. High D-dimer levels can also be caused by factors other than clotting disorders, such as pregnancy, heart disease, rheumatoid arthritis, or recent surgery. Furthermore, anticoagulant medications can affect D-dimer test results, leading to false negatives.

If the D-dimer test result is positive, the healthcare provider will consider the patient's symptoms, medical history, and the results of other tests to determine the next steps. Additional tests will be needed to identify the location of the blood clot and the specific type of clotting disorder.

Magnetic resonance imaging (MRI)

MRI is particularly useful for detecting blood clots because it can highlight differences between various types of tissues within the body. Blood clots can appear differently depending on their stage and location, and MRI can make these differences more visible.

Specific MRI techniques, such as Magnetic Resonance Venography (MRV) and Magnetic Resonance Angiography (MRA), are designed to image the body's veins and arteries, providing detailed views that help identify clots. These techniques can visualize blood flow or the lack thereof, and clots show up as blockages or abnormalities in the normal flow patterns.

MRI is not typically the first-line diagnostic tool for all types of clots due to its cost and accessibility. Ultrasounds, for example, are often used for detecting deep vein thrombosis (DVT) in the legs. However, for complex cases or when clots are suspected in less accessible areas of the body, MRI provides a non-invasive and detailed examination method without exposing the patient to radiation.

In summary, MRI is a valuable tool for detecting blood clots, especially in complex or hard-to-reach areas of the body, as it can provide detailed images of internal structures and highlight differences between tissues, making clots more visible.

Computed tomography (CT) scan

A computed tomography (CT) scan is an imaging test that uses a series of X-rays and a computer to create detailed images of bones and soft tissues inside the body. CT scans are non-invasive, painless, and can detect injuries and diseases. They are particularly useful for diagnosing circulatory (blood) system diseases and conditions, such as blood clots, as well as spinal conditions, kidney and bladder stones, and inflammatory diseases.

During a CT scan, the patient lies very still on a table, which passes slowly through the center of a large, donut-shaped X-ray machine. The machine takes X-ray pictures from dozens to hundreds of angles as it revolves around the patient. The patient might hear whirring sounds during the procedure and may be asked to hold their breath at times to prevent blurring of the images.

CT scans can be performed with or without contrast material. In a CT scan with contrast, a dye is injected into a vein through an intravenous (IV) line to highlight certain areas of the body. The patient may also be given a substance to drink, such as a barium swallow, to highlight their intestines. These contrast agents improve the visibility of specific tissues, organs, or blood vessels and help with diagnosis.

In the case of suspected blood clots, a CT angiography (CTA) scan of the chest, abdomen/pelvis, or head may be performed to help diagnose the condition. CT angiography can detect blood clots by visualizing the blood flow through veins and arteries. It is particularly useful for detecting pulmonary embolisms, which are caused by fragments of blood clots that have broken off and traveled through the veins to the lungs.

Frequently asked questions