Vascular Testing

Aorta Duplex Imaging

Most abdominal aortic aneurysms produce no symptoms (they are asymptomatic). They are often incidentally discovered when abdominal ultrasounds and/or CT scan studies are ordered for other conditions. When they produce symptoms, the most common symptom is pain. The pain typically has a deep quality as if it is boring into the person. It is felt most prominently in the middle of the abdomen and can radiate to the back. The pain is usually steady but may be relieved by changing position. The person may also become aware of an abnormally prominent abdominal pulsation.

Abdominal aortic aneurysm can remain asymptomatic or produce mild to moderate symptoms for years. However, a rapidly expanding abdominal aneurysm can cause sudden onset of severe, steady, and worsening middle abdominal and back pain. A rapidly expanding aneurysm is also at imminent risk of rupture. Actual rupture of an abdominal aneurysm can cause sudden onset of back and abdominal pain, sometimes associated with abdominal distension, a pulsating abdominal mass and even shock (severe low blood pressure due to massive blood loss).

Arterial Duplex

Peripheral arterial disease is estimated to affect approximately 8 - 12 million individuals in the United States. Originally, the purpose of the noninvasive arterial evaluation was to offer objectivity in the diagnosis of lower extremity arterial disease. It was intended to complement but not to replace a careful history and physical examination of the patient. Currently, after decades of evolution, the noninvasive arterial evaluation may be tailored to a patient's specific needs, depending on the clinical presentation and the pathologic findings being evaluated.

Arterial duplex imaging provides direct anatomic and physiologic information, but it does not provide information regarding overall limb hemodynamics. Duplex imaging distinguishes between a stenosis and an occlusion, determines the length of the disease segment and patency of the distal vessels, evaluates the results of intervention (angioplasty, stent placement), diagnoses aneurysms and pseudoaneurysms, and monitors a patient's postoperative course with continuing bypass graft surveillance.

Carotid Duplex

Carotid duplex imaging is now recognized as the best non-invasive screening test for carotid artery stenosis. The evidence for its use as the sole diagnostic imaging modality prior to carotid endarterectomy is examined. Providing it is carried out by experienced trained operators using validated duplex criteria, carotid duplex imaging is safe, highly sensitive and specific, and superior to angiography at plaque characterization and evaluation of flow disturbance.

Transcranial Doppler, Cerebral CT and MRI should be performed if symptoms are atypical or if there is an evolved stroke. Angiography is required when duplex imaging is suboptimal or equivocal, in the presence of atypical symptoms or uncommon vascular abnormalities. In the majority of patients requiring endarterectomy for symptomatic high grade ICA stenosis, angiography seldom adds relevant information, and clinical assessment and carotid duplex imaging alone can be safely used in preoperative assessment.

Transcranial Doppler

Transcranial Doppler (TCD) is a test that measures the velocity of blood flow through the brain's blood vessels. Used to help in the diagnosis of emboli, stenosis, vasospasm from a subarachnoid hemorrhage (bleeding from a ruptured aneurysm), and other problems, this relatively quick and inexpensive test is growing in popularity in the United States. The equipment used for these tests is becoming increasingly portable, making it possible for a clinician to travel to a hospital, doctor's office or nursing home for both inpatient and outpatient studies. It is often used in conjunction with other tests such as MRI, MRA, carotid duplex ultrasound and CT scans.

Cerebrovascular Diseases can be realistically explored and studied with the use of Transcranial Doppler. We perform a comprehensive and detailed protocol for understanding and interrogating a wide variety of neurovascular pathology:

    * Carotid stenosis/occlusion
    * Intracranial Stenosis
    * Cerebral Emboli Detection
    * Cerebral Vasospasm
    * Arteriovenous Malformations
    * Head Trauma
    * Cerebral Circulatory Arrest
    * Diminished Vasomotor Reactivity
    * Reduced/Absent Cerebral Autoregulation
    * Variations in Circle of Willis

Advantages and Limitations of TCD

TCD is relatively inexpensive, noninvasive, portable and fairly easy to use. It allows frequent repeated measurements and continuous monitoring. Immediate, real time detection of changes in cerebrovascular hemodynamics is possible. It can be utilized by any medical specialty to evaluate several neurovascular disorders.

In many communities (especially rural ones), there is no neurologist and/or MRI machine available for appropriate stroke workup. In those settings and in many other places a "complete" stroke workup consists of carotid Doppler and two-dimensional echocardiogram. This misses the important evaluation of intracranial vasculature. A TCD may be the inexpensive, simple mean to determine which patients must be referred to a specialized center for further evaluation. In addition, and in patients who decline intervention initially, TCD gives a tool for monitoring the identified lesions through the years and evaluate the effectiveness of medical treatment.

Finally, TCD may be the only mean possible to evaluate intracranial vessels in cases when other radiographic means are contraindicated. TCD is a "blind procedure"; its accuracy relies on the knowledge and experience of a trained technician and interpreter. It has limited ability to detect distal branches of intracranial vessels. In 5% to 10% of cases, sufficient penetration of the bone window cannot be achieved for ample insonation.

Renal Ultrasound

Acute flank pain and abdominal pain with hematuria are relatively common presenting complaints in the ultrasound department. Although urinary obstruction is a likely diagnosis in such patients, the differential diagnosis includes life-threatening disease processes, most importantly an expanding or ruptured abdominal aortic aneurysm. Emergency bedside sonography is a tool that can rapidly confirm the diagnosis of acute urinary obstruction and help exclude life-threatening processes.

It is important to know common medical terms used to describe the pathophysiology of urinary retention. The structural impediment to the flow of urine is termed obstructive uropathy. Unless this obstruction develops slowly it is typically painful, which is called renal colic. The most common cause is a kidney stone dislodged into the ureter called ureterolithiasis. Urine flow is blocked by the stone leading to back-up and dilation of the proximal ureter (hydroureter). As the obstruction progresses, more proximal structures like the renal collecting system (renal pelvis and calyces) becomes dilated, termed hydronephrosis. If the hydronephrosis is severe, the renal parenchyma becomes compressed and if lasting long enough (about 2-4 weeks), can cause loss of renal function.

As described above, the most common cause of renal colic and hydronephrosis is ureterolithiasis. But in general everything able to obstruct the inner lumen of the collecting system or causing extrinsic compression can block urinary flow and lead to renal colic.

Bedside renal sonography in the ultrasound department is also useful in the patient presenting with decreased urinary output or anuria, acute renal failure or pyelonephritis. Similar to the renal colic patient it allows the examiner to narrow the differential diagnosis by evaluating the retroperitoneal anatomical structures for abnormalities but gives only limited clues for the functional status of the urinary system.

Venous Duplex

The most common reason for a venous ultrasound exam is to search for blood clots, especially in the veins of the leg. This condition is often referred to as deep vein thrombosis or DVT. These clots may break off and pass into the lungs, where they can cause a dangerous condition called pulmonary embolism. If found in time, there are treatments that can prevent this from happening.

A venous ultrasound study is also performed to:
  • determine the cause of long-standing leg swelling. In people with a common condition called varicose veins, the valves that keep blood flowing in the right direction may not work well, and venous ultrasound can help the surgeon decide how best to deal with this condition.
  • aid in the placement of a needle or catheter in a large interior vein. Sonography can help locate the exact site of the vein and avoid complications, such as bleeding or air in the chest cavity.
  • map out the veins in the leg or arm so that segments may be removed and used to bypass an area of disease. An example is using pieces of vein from the leg to surgically bypass narrowed coronary arteries.
  • examine a blood vessel graft used for dialysis if it is not working as expected; an area of narrowing in the graft may be responsible.

Doppler ultrasound images can help the physician to see and evaluate:

    * blockages to blood flow (such as clots)
    * venous insufficiency (reflux)
    * narrowing of vessels (which may be caused by plaque)
    * tumors and congenital malformation

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