Figure 87-26. Venous flow is typically depicted below the baseline. Venous flow in the proximal lower extremity veins should be

spontaneous, vary with respiration, and augment with distal compression.

At a minimum, vascular laboratory duplex ultrasound evaluation for lower extremity DVT should

include examination of the common femoral, profunda femoris, femoral, and popliteal veins. Venous

waveforms from the right and left common femoral veins should always be compared. A normal lower

extremity examination will show patency of the veins on color flow imaging, collapsing of the veins

with application of pressure by the ultrasound probe and venous flow patterns in the common femoral

and femoral veins that decrease with inspiration and increase with expiration. Flow within a patent vein

should also increase with application of compression distal to the site of examination (Fig. 87-26).

9 The primary ultrasound diagnostic criteria for diagnosis of venous thrombosis is failure of the vein

to collapse with application of pressure with the ultrasound probe (Fig. 87-27A,B). A continuous flow

pattern in one common femoral vein and not the other suggests ipsilateral iliac vein thrombosis or

external compression of the ipsilateral iliac vein. Bilateral pulsatile common femoral waveforms suggest

volume overload, tricuspid regurgitation, or heart failure.

Not all venous ultrasound examinations for DVT are the same. Some vascular laboratories do not

include evaluation of the calf veins as part of their routine evaluation for lower extremity DVT, even in

symptomatic patients. This results from outdated perceptions of inaccuracy of calf vein ultrasound

evaluation for DVT. Failure to perform a complete initial examination necessitates serial ultrasound

examinations or alternative strategies to detect possible extension of venous thrombi initially isolated to

the calf veins. Such strategies are inefficient, ineffective for noncompliant patients, and not cost

effective compared to a single stand-alone color flow duplex study of the proximal and calf veins in

patients with suspected lower extremity DVT.

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Figure 87-27. A: Without compression with the ultrasound probe the femoral vein is easily visible (white arrow). B: With

compression the vein collapses and is no longer visible (black arrow). Failure of the vein to collapse with probe pressure would

indicate the presence of thrombus within the vein.

Limited ultrasound studies for acute DVT may include compression ultrasound (B-mode imaging

only), duplex ultrasound (B-mode imaging and Doppler waveform analysis), and color Doppler alone.

The sensitivities and specificities for detecting acute DVT differ among the examinations, and different

examinations are appropriate for different veins. Compression ultrasound is typically performed for

evaluation of proximal deep veins, specifically the common femoral, femoral, and popliteal veins. A

combination of duplex ultrasound and color Doppler is more often used for calf and iliac veins. Color

flow alone may be used to assess patency of the calf veins as they are difficult to reliably compress in

subjects with larger legs.

Many factors will influence which venous segments can be evaluated in an individual examination.

These include the presence of morbid obesity, lower extremity edema or tenderness, or the presence of

immobilization devices and bandages. Overall, a complete color and Doppler examination has become

the standard of care for assessment of lower extremity DVT. It is recommended that whenever possible,

a venous duplex examination to exclude the presence of DVT consist of an evaluation of both the

proximal and calf veins.

A well-trained technologist can interrogate calf veins in 80% to 98% of cases using a combination of

B-mode, Doppler waveform analysis, and color Doppler.78,79 Overall accuracy of venous

ultrasonography in comparison to venography has been well established. The weighted mean sensitivity

and specificity of venous ultrasonography (including all types) for the diagnosis of symptomatic

proximal DVT are 97% and 94%, respectively.77 As suggested above, in technically adequate studies, the

sensitivity and specificity of color Doppler to identify isolated calf vein thrombosis exceeds 90%.79 The

high specificity of venous ultrasonography allows treatment for DVT to be initiated without further

confirmatory tests, and the high sensitivity in diagnosing proximal DVT makes it possible to withhold

treatment if the examination is negative.

Some ultrasound examinations are limited by practical constraints. Inability of the patient to fully

cooperate with regard to positioning for the examination and/or intolerance of the pressure of the

ultrasound scan head on the skin, or inability of the examiner to obtain a complete examination

secondary to bandages, casts, or extremity wounds, may lead to a requirement for serial examinations.

An alternative diagnostic procedure, such as catheter-based contrast, MR, or CT venography may be

indicated when a complete ultrasound examination is not possible or if the patient cannot or is unlikely

to return for a follow-up examination. Currently, repeat or serial venous ultrasound examinations are

advisable in follow-up for a limited negative examination in symptomatic patients highly suspicious for

DVT in whom an alternative form of imaging is unavailable or contraindicated.

The diagnosis of pulmonary embolism (PE), like that for DVT, also cannot be established without

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objective testing. Several studies have evaluated lower extremity venous ultrasound examinations in

patients suspected of PE. These studies, often employing ultrasound of only the proximal veins and

nuclear medicine-based ventilation perfusion (V/Q) scanning, unfortunately have little relevance to

modern practice where complete proximal and distal vein ultrasound examinations are usually routine,

and where CT pulmonary angiography (CTPA) or MR pulmonary angiography (MRPA) have largely

supplanted V/Q scanning.

The rationale for venous ultrasonography in patients who present with symptoms of PE is that a

diagnosis of DVT may indirectly suggest a diagnosis of PE, making additional investigation to exclude

PE unnecessary in some clinical settings. However, ultrasound cannot make a definitive diagnosis of PE.

Patients can have DVT and pulmonary symptoms or hemodynamic instability from causes other than PE.

Normal bilateral proximal venous ultrasound scans do not rule out PE. When PE is definitively

present, DVT of the proximal lower extremity veins is detectable by compression ultrasound in only

50% of patients.80 When a PE is objectively diagnosed with no evidence of lower extremity DVT, the PE

may have originated from pelvic veins, arm veins, or possibly embolized completely from a lower

extremity vein. An objective diagnostic test for PE is therefore indicated in most cases. Currently, in

most centers this would be a CT pulmonary angiogram.

Chronic Venous Insufficiency (CVI)

The presence of venous insufficiency can also be evaluated with either air or photoplethysmography and

with duplex scanning.81 In theory, air plethysmography (APG) can provide an analysis of overall venous

hemodynamics including evaluation of the individual components of venous function; reflux and the

efficacy of the calf muscle pump. A flexible chamber is placed on the calf and volume changes then

induced by a series of positional and exercise maneuvers. Measurements derived from these maneuvers

are then used to calculate measures of venous reflux (venous filling index [VFI]), calf muscle pump

function (ejection fraction [EF]) as well as a measure of overall venous function termed the residual

volume fraction. Of these values VFI has the potential for being the most important. A VFI of >2 mL/s

indicates abnormal reflux with values >10 mL/s indicating increased risk of cutaneous changes

associated with chronic venous insufficiency. APG, however, while theoretically interesting, is used only

infrequently in clinical practice.

Photoplethysmography (PPG) is a variant of plethysmography techniques to assess venous reflux. It

detects changes in the blood content of the skin that theoretically reflect venous volume. It consists of a

light emitting diode and a photo sensor. The diode transmits light into subcutaneous tissues. Blood

attenuates light in proportion to its content in tissue. The PPG machine amplifies the difference between

the transmitted and reflected signal and converts it into a waveform. To assess for venous reflux the

sensor is typically applied to the medial ankle area (Fig. 87-28). The patient performs a series of plantar

and dorsal flexion maneuvers of the foot decreasing the venous volume of the extremity. The time for

the waveform to return to baseline is termed the venous recovery time (VRT). A normal PPG VRT is 20

seconds or greater. Shorter times indicate the presence of venous reflux. If the VRT returns to normal

with the application of a superficial venous tourniquet then the reflux is confined to the superficial

venous system (Fig. 87-29). If the VRT does not correct with a superficial venous tourniquet deep

venous reflux is present. Neither, APG or PPG can provide information about the specific venous

segments that are abnormal. That information can be provided by duplex ultrasound.

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Figure 87-28. Placement of PPG probes for assessment of venous reflux.

Figure 87-29. Venous PPG waveforms in a patient with superficial venous reflux. The patient is asked to perform 10 dorsal and

plantar flexions of the ankle resulting in emptying the leg of venous blood. In the top panel the veins refill very rapidly indicating

the presence of venous reflux. Refill slows with application of a tourniquet to occlude the superficial veins indicating this patient

likely has only reflux in the superficial venous system and no deep venous reflux.

10 Duplex ultrasound can provide important physiologic and anatomic information in patients with

possible CVI. Both sites of reflux and of venous obstruction can be determined in deep, superficial, and

perforating veins. In patients with valve incompetence, reflux can be stimulated and then detected with

duplex using a Valsalva maneuver, manual compression proximal to the transducer, or release of

compression distal to the transducer. The examination has been standardized with the patient upright

and using deflation of a series of pneumatic cuffs at specific sites on the leg with the leg under

examination not bearing weight. In the upright position, reflux stimulated by cuff deflation that lasts

more than 0.5 second is indicative of pathologic reflux.82 The technique allows localization of reflux to

specific venous segments and can serve as a valuable preoperative planning tool to target specific

venous segments for removal or reconstruction (Fig. 87-30). It has a sensitivity of 82% and specificity

of 100% for the identification of competent and incompetent perforating veins. Duplex determination of

reflux sites and sites of venous occlusion as a means of assessing overall venous hemodynamics is not

established. Currently duplex assessment of venous reflux provides the basis of planning for the large

majority of venous procedures designed to treat the manifestations of superficial venous reflux.

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Figure 87-30. Popliteal venous waveform with cuff deflation for duplex assessment and localization of venous reflux. Reflux

lasting >0.5 to 1 second is abnormal.

SELECTED MISCELLANEOUS EXAMINATIONS

Evaluation for Abdominal Aortic Aneurysm

Vascular laboratory ultrasound screening for abdominal aortic aneurysm (AAA) in males >65 years

with a history of cigarette smoking has been shown to be effective in preventing aneurysm related

deaths in this cohort.83 Ultrasound is highly accurate and reproducible in measuring the diameter of

infrarenal AAAs (Fig. 87-31). Typically patients with AAA diameters below accepted threshold levels for

repair are followed with serial ultrasound examinations to monitor for enlargement of the aneurysm to

a diameter where repair is indicated.

Figure 87-31. Ultrasound image of a 5.9-cm infrarenal abdominal aortic aneurysm with acentric intraluminal thrombus.

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Figure 87-32. Ultrasound examination of an aortic stent graft. The aortic stent graft (arrows) is visible within the lumen of the

residual aneurysm sac measuring 8.36 cm × 7.99 cm.

Evaluation of Aortic Endografts

Placement of endoluminal stent grafts is now standard therapy for most patients with AAA. With stent

grafting of an AAA the aneurysm is left in situ and blood flow diverted through the stent graft. Some

stent grafts eventually leak at proximal or distal attachment sites. AAAs with these so-called type I

endoleaks are at increased risk of rupture. In addition, AAAs treated with stent grafts may also

occasionally enlarge because of back pressure in the aneurysm sac from patent lumbar vessels; type II

endoleak. Patients whose AAAs enlarge in association with type II endoleaks after endografting are also

considered at risk for aneurysm rupture.

Standard monitoring of endoluminal stent grafts is with serial CT scans to detect endoleak and

changing aneurysm sac diameter. However, there are increasing concerns about repeated doses of

contrast and radiation exposure associated with serial CT scans. It now appears many stent grafts can be

followed with serial duplex ultrasound examinations. Duplex ultrasound is capable of measuring sac

diameter (Fig. 87-32) and detecting both type I and II endoleaks. Even if an endoleak cannot be

detected by ultrasound an increase in sac diameter following stent grafting should prompt further

investigation. In some centers duplex ultrasound has replaced CT scanning as the preferred method of

follow-up of AAA stent grafts.84,85

Evaluation and Treatment of Groin Pseudoaneurysms

Pseudoaneurysms can occur as a complication of an arterial puncture in the groin performed for

diagnostic or therapeutic angiography. Groin pseudoaneurysms are readily detected with duplex

ultrasound (Fig. 87-33). Color flow demonstrates a typical collection of flowing blood usually anterior

to the artery from which the psuedoaneurysm originates. The native artery and the pseudoaneurysm are

connected by a so-called “neck.” To-and-fro flow within the neck of the pseudoaneurysm is

characteristic and pathognomonic of a pseudoaneurysm arising from an arterial puncture.

Treatment of pseudoaneurysms may be with direct surgical repair or, utilizing the vascular

laboratory, direct compression of the pseudoaneurysm until it clots using the ultrasound scan head to

both locate the pseudoaneurysm and apply pressure. Alternatively, the pseudoaneurysm is visualized

with the ultrasound scan head and a needle introduced into the body of the pseudoaneurysm for

injection of small amounts of thrombin to induce thrombosis of the pseudoaneurysm.86 All techniques

are effective but currently direct thrombin injection is favored in most cases as it is relatively

noninvasive and less painful and more effective than prolonged compression alone.87,88

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Figure 87-33. A pseudoaneurysm of the superficial femoral artery following arterial cannulation. The so-called neck of the

aneurysm (arrow) is readily visible.

Transcutaneous Oxygen (TCpO2) Measurements

Measurements of transcutaneous oxygen can be performed as an aid in predicting healing of pedal

lesions or healing of an amputation at the site where the measurement is taken (Fig. 87-34). In general,

a TCpO2 >30 mm Hg indicates healing is likely, measurements between 20 and 30 mm Hg are

equivocal for healing and measurements below 20 mm Hg indicate healing is unlikely.89 Measurements

are not influenced by the presence of diabetes but it has been suggested the level for predicting healing

be increased to 40 mm Hg in patients with diabetes. The test is less accurate in the presence of edema,

cellulitis, hyperkeratosis, and in older patients.

Figure 87-34. A transcutaneous oxygen probe. TCpO2 measurements can serve as an aid in determining healing potential of pedal

wounds or ulcers.

References

1. Roederer GO, Langlois YE, Chan AT, et al. Ultrasonic duplex scanning of the extracranial carotid

arteries: improved accuracy using new features from the carotid artery. J Cardiovasc Ultrasonography

1982;1:373–380.

2. Abou-ZamZam AM Jr, Moneta GL, Edwards JM, et al. Is a single preoperative duplex scan sufficient

for planning bilateral carotid endarterectomy? J Vasc Surg 2000;31:282–288.

3. Strandness DE Jr. Duplex Scanning in Vascular Disorders. New York, NY: Raven Press; 1990:92–120.

4. Roederer GO, Langlois YE, Jager KA, et al. A simple spectral parameter for accurate classification

of severe carotid artery disease. Bruit 1989;3:174–178.

5. Moneta GL, Edwards JM, Chitwood RW, et al. Correlation of North American Symptomatic Carotid

Endarterectomy Trial (NASCET): angiographic definition of 70% to 90% internal carotid artery

stenosis with duplex scanning. J Vasc Surg 1993;17:152–159.

6. Bendick PJ, Glover JL. Hemodynamic evaluation of the vertebral arteries by duplex ultrasound.

Surg Clin North Am 1990;70:235–244.

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