Duplex ultrasound is used to assess the arteries of the leg for the presence of atherosclerosis (disease and narrowing of the arteries). Patients with significant narrowing or occlusion of the arteries in the abdominal aorta, iliac arteries and arteries of the leg often experience claudication. Claudication is the experiencing of pain or cramping of the buttock, thigh or calf when the patient is exercising. As the patients exercise the demand for blood supply to the muscles of the leg is increased. If the arteries are narrowed or occluded then the blood supply cannot meet the demand and the patient experiences claudication. Generally, the shorter the distance the patient is able to walk before they have to stop due the claudication the greater the severity of the narrowing or blockage. If the blockages are severe enough the patient can experience pain in the leg and foot at rest and in worst cases, suffer from wounds on the leg and feet that will not heal.
Duplex ultrasound can identify and estimate the degree of stenosis and the site of the stenosis. The arteries can also be assessed for the presence of dilatation or aneurysm and measurement of the size of the aneurysm.
Duplex ultrasound of the lower limb arteries can be performed for screening purposes (family background of atherosclerosis or aneurysmal disease), claudication, diabetic and high risk foot patients, poor healing of leg wounds and poor or absent foot pulses. Duplex ultrasound of the arteries is also necessary after treatment of diseased arteries by angioplasty, stenting or bypass. A careful surveillance program after treatment can greatly assist maintaining artery and graft patency.
PATIENT PREPARATION AND EXAMINIATION TECNIQUE:
If duplex ultrasound assessment of the aorta and iliac arteries (abdominal duplex) is required the patient will need to fast for 6 hours. This is to ensure that bowel gas is reduced as much as possible to ensure the best possible image of these arteries. If the patient is diabetic food can be brought to consume after the examination. All medications can still be taken with a small amount of water.
The patient is examined in a quiet, darkened room with privacy ensured. The patient will need to remove clothing from the legs, leaving underwear on. The study is non-invasive and painless and does not involve needles. Gel is applied to the skin and the ultrasound probe is moved over the skin of the abdomen and leg. The arteries of the abdomen and legs are imaged with B-mode and Doppler ultrasound. The arteries are assessed for patency, size and whether atherosclerosis is present. The speed of the blood flow in these arteries is measured and used to estimate the degree of narrowing of the artery. All blood flow velocity measurements and site of significant narrowing of the arteries is recorded and a detailed worksheet and report generated.
Examination of the abdominal aorta and bilateral leg arteries can take up to 60-90minutes. It may be necessary on occasions to do some of the examinations on separate days.
Degree of stenosis in the peripheral arteries is classified as <50%, >50%, >75% and occlusion.
Sites of stenosis or occlusion are measured against anatomical landmarks and length of occlusion measured.
For peripheral arterial aneurysms – aneurysm size, location and the presence or absence of mural thrombus is noted.