What Is a Non-Invasive Ultrasound Lower Extremity?
Ultrasound is used primarily two ways:
- To generate heat for therapy of tendinopathies and myositis
- For non-invasive diagnostic imaging
The efficacy for musculoskeletal inflammation varies from patient to patient, but the benefits of ultrasound for diagnosing abnormal conditions of the cardiovascular system is well established.
Using the reflections of sound waves thousands of times faster (frequency) than those within the normal hearing range, an image can be rendered using the differences in these reflections. These differences are a result of the varying tissue densities of the structures that are struck and reflected. Ultrasound diagnostics have proved invaluable in pursuing conditions in the vascular system, from venous blood clots (thrombi) to arterial aneurysms and stenosis. The science of cardiac echocardiography has revolutionized the identification and management of cardiac disease.
Doppler technology takes advantage of differences rendered by motion. Doppler ultrasound, as opposed to regular ultrasound, is used to detect blood flow within arteries and veins and is useful in identifying problems of venous and arterial circulation.
The Lower Extremity
Due to gravity and the amount of blood that can pool within them, the legs present the biggest risk to the blood flow that is part of the circulation returning blood back to the heart. Compared to the arterial system, veins have a lower pressure for movement of the blood but are assisted by the presence of valves to prevent backflow and the compression/decompression of the leg muscles in ambulation and other movement that propagates blood upward. The heart is the primary pump, and the leg musculature serves as a secondary pump of the human body.
Deep Vein Thrombosis (DVT)
When this secondary pump fails, due to immobilization, coagulation abnormalities, or for unknown reasons, thrombi can form which pose a risk for separation from their thrombotic beds and migrating to the heart as emboli. The return of emboli to the right side of the heart propels them to the lungs along with the deoxygenated blood that carries them. This can result in varying degrees of obstruction in the ventilation process, from dyspnea to death.
Peripheral Arterial Disease
Atherosclerotic plaque formation and inflammatory conditions threaten the blood supply to the tissues distal from the narrowing or obstruction. This can cause ischemia, necrosis, ulceration, and possible sepsis.
Ultrasound of the Lower Extremity
Ultrasound is the preferred method of diagnosing thrombi when thrombophlebitis is suspected. It is also the first diagnostic choice for complications or identification of peripheral arterial disease. Other diagnostic modalities include MRI and CT, but ultrasound is the simplest, most cost-effective, and easiest to perform.
Diagnosis of a Non-Invasive Ultrasound of the Lower Extremity
Duplex ultrasound is a combined ultrasound of two different types:
- B-mode (or brightness mode) ultrasound
- Doppler flow detection ultrasound, either as pulsed or continuous ultrasound waves
Regular ultrasound renders images of structures within the leg and Doppler ultrasound, using the same scanning transducer, reflects high frequency sound waves off of red blood cells in motion. Duplex ultrasound is used for identifying
- Blood clots in the deep veins of the legs
- Circulation impairment: Such as arterial obstruction or venous stasis
- Venous insufficiency (impaired venous valves): Which can lead to stasis
- Arterial abnormalities: Such as occlusion, eripheral arterial disease, aneurysms, or stenosis
Deep Vein Thrombosis (DVT) Diagnosis and Testing
The most common symptom of deep vein thrombosis is swelling (edema) of the leg. It is usually unilateral, but may be bilateral. A tape measure is used to document the circumference of the calf or thigh and compare it to the non-involved leg.
Pain and warmth are frequently associated symptoms. DVT can be suspected on clinical grounds if these signs and symptoms occur, along with tenderness upon squeezing the leg. For establishing the diagnosis, ultrasound is the diagnostic modality of choice.
Peripheral Venous Disease (PVD) Diagnosis and Testing
PVD of the lower leg is the most common vascular disorder. It encompasses venous dilation/varicosities and venous reflux/venous valve insufficiency.
Complications of PVD aid in its clinical diagnosis and include acute and chronic ulcerations, local infection, and sepsis. Diagnosis is based on clinical signs and symptoms and ultrasound.
Peripheral Artery Disease (PAD) Diagnosis and Testing
Claudication is a symptom that presents as muscle pain with activity, indicating that the extra oxygen demand of muscle actions is not being met. PAD is the accumulation of plaques that can narrow or block the arterial blood supply, leading to claudication, ischemia, or necrosis.
Symptoms are often similar to those of deep vein thrombosis or thrombophlebitis, and ultrasound is used to differentiate PAD from DVT. Diagnosis via duplex ultrasound can identify arterial disease, from the femoral artery, popliteal, and lower branches up to and including the higher aortoiliac vessels.
Blood work to assess coagulation, glucose, liver function, blood count, etc., are not particularly useful in diagnosing vascular disease, but can serve as a clue for its underlying cause.
Management and Treatment of Peripheral Venous Disease (PVD)
PVD includes thrombophlebitis and thrombosis (deep vein thrombosis–DVT) and venous stasis due to the impairment of the venous valves (venous insufficiency).
For DVT, whether to offer anticoagulation therapy is based on a risk assessment, but when warranted uses agents such as warfarin, clopidogrel (Plavix), etc., to discourage further thrombosis as well as dissolve current clots. The complication of DVT that is life-threatening is pulmonary embolism, which makes DVT a serious condition warranting early diagnosis and treatment.
For venous insufficiency and varicosities, leg elevation, compression stockings, ambulation and exercise, and–for diabetics–strict glycemic control are used to mitigate painful and cosmetic issues and increase oxygen transport to the skin. If venous insufficiency progresses to venous ulceration, ulcer wound management, compression, and bandaging systems are used. Vein excision and ablation may be necessary. If there is any infection to the overlying skin or associated with ulceration, this is cultured and treated with antibiotics accordingly.
Management of Peripheral Arterial Disease (PAD)
PAD includes the symptoms of claudication and paresthesias (numbness or tingling), as well as signs of ischemia and necrosis. Most at risk are the terminal branches of the arterial tree–the distal fingers and toes, but in the leg signs and symptoms can range from the iliac arteries to the tibial vessels.
Any plaque build-up due to atherosclerosis can result in partial or complete obstruction, requiring surgical correction to re-establish blood flow. More conservative measures are smoking cessation, diet and nutrition, and supervised exercise.
Prevention of PVD
In Conditions Diagnosed with Lower Extremity Ultrasound
- Peripheral venous disease (PVD: thrombus, thrombophlebitis, and emboli; venous stasis, insufficiency, and ulceration)
- Peripheral arterial disease (PAD: claudication, obstruction, ischemia)
Their prevention is as important as treating their underlying conditions.
Peripheral Venous Disease (PVD)
Venous valves deteriorate with age and become incompetent. Prevention of age-related PVD is based on counteracting this with continued activity of the lower extremity, including exercise and ambulation, in order to keep the “secondary pump” action of the leg musculature functioning to move blood back up toward the heart. Compression stockings, leg elevation, and avoiding trauma to the legs are important. Smoking cessation and weight management improve PVD and prevent further progression.
Complications of PVD include acute and chronic ulcerations, local infection, sepsis, and deep vein thrombosis (DVT) and pulmonary emboli. Diagnosis is based on clinical signs and symptoms and ultrasound. Any ulceration should be aggressively managed to eliminate risk to contiguous tissues or systemic spread of infection.
Risks for both PVD and DVT include immobilization, lengthy convalescence, or prolonged hospitalization; age >65 years, obesity, previous thrombosis or thromboembolism, malignancy, family history of venous thrombosis, autoimmune disease and inflammatory bowel disease, smoking, previous trauma to the leg(s), and–in women–the high estrogenic state that results from pregnancy, oral contraceptives, or menopausal hormone replacement.
Peripheral Arterial Disease
Risks for Arterial Disease are atherosclerosis, arteritis, smoking, obesity, diabetes, high cholesterol, and hypertension.
Hypertension and cardiovascular arterial disease are managed/prevented by the use of antihypertensive medications, smoking cessation, avoidance of hyperglycemia (especially in diabetics), and weight management to improve the comorbidity of metabolic syndrome. Exercise is important in preventing further progression and in reducing the PAD and/or the hypertension responsible for plaque formation and arterial blood flow compromise due to narrowing or occlusion.