Laboratory Studies
Many patients with venous insufficiency have clinically unrecognized chronic recurrent varicose thrombosis due to stasis in areas with abnormal veins. Such patients may have elevated levels of D-dimer. This finding reduces the usefulness of that test for the evaluation of patients with suspected acute venous thromboembolic disease.
Laboratory tests may be helpful in patients with venous insufficiency due to Klippel-Trénaunay-Weber (KTW) syndrome because such patients can develop consumptive thrombocytopenia.
Ultrasonography
Duplex ultrasonography is the study of choice for the evaluation of venous insufficiency syndromes. Color-flow duplex imaging uses the Doppler information to color code the 2-dimensional sonogram. On the image, red indicates flow in one direction (relative to the transducer), and blue indicates flow in the other direction. [19] On newer machines, the shade of the color may reflect the flow velocity (in the Doppler mode) or the flow volume (in the power Doppler mode).
When used to evaluate patterns of venous reflux, ultrasonography is both sensitive and specific. Ultrasonographic reflux mapping is essential for the evaluation of peripheral venous insufficiency syndromes.
A study from the United Kingdom compared 27 consecutive patients seen at a varicose vein clinic with 23 normal ambulatory volunteers and found evidence to suggest that the presence of pulsatile flow in the GSV might be a marker of severe chronic insufficiency of the superficial veins. [20]
In the diagnosis of deep venous thrombosis (DVT), ultrasonography has been shown to be superior to contrast venography, and it has now replaced venography in this setting. Duplex ultrasonography is the initial diagnostic imaging modality of choice in patients with suspected DVT.
Intravascular ultrasonography has been gaining acceptance in the management of venous disease. This test uses a catheter-based ultrasound probe to visualize periluminal vascular anatomy in order to assess for obstructive or stenotic disease of the venous system. [21]
Venography
Magnetic resonance venography (MRV) is the most sensitive and specific test for the assessment of deep and superficial venous disease in the lower legs and pelvis, areas not accessible by means of other modalities. MRV is particularly useful because it can help detect previously unsuspected nonvascular causes of leg pain and edema when the clinical presentation erroneously suggests venous insufficiency or venous obstruction.
Current advances in technology have allowed the inclusion of computed tomography and/or MRV in the evaluation of venous disease; however, their use requires intravenous contrast material and appropriate timing in order to obtain a venogram. In other words, a proper technique that would allow the proper visualization to assess for obstructive disease, varicose veins, perforating veins, and other venous abnormalities is required. [21]
Direct contrast venography (see the image below) is a labor-intensive and invasive imaging technique. In most centers, it has been replaced by duplex sonography for the routine evaluation of venous disease. However, the technique remains useful in difficult or confusing cases.
An intravenous (IV) catheter is placed in a dorsal vein of the foot, and radiographic contrast material is infused into the vein. A superficial tourniquet is placed around the leg to occlude the superficial veins and force the contrast material into the deep veins.
The assessment of reflux by means of direct contrast venography requires the passage of a catheter from the ankle to the groin with the selective introduction of contrast material into each segment of the vein.
In nearly 15% of patients undergoing venography for detection of DVT, a new thrombosis is detected shortly after a contrast venogram shows negative results. The incidence of contrast-induced DVT in patients who undergo venography for the assessment of venous insufficiency is not known.
Venous Plethysmography
Air plethysmography (APG) is a noninvasive test that has the ability to measure some pathophysiologic mechanisms of CVI, which includes reflux, obstruction, and muscle pump dysfunction. This test facilitates evaluation of venous filling through the venous filling index. It may be useful when venous duplex ultrasound does not provide conclusive information. [21]
Photoplethysmography uses infrared light to assess capillary filling during exercise. Increased capillary filling is indicative of venous reflux and, consequently, of incompetent veins.
Outflow plethysmography involves placing and subsequently releasing a tourniquet on the lower extremity; the veins should quickly return to baseline pressures. Failure to do so indicates reflux.
Physiologic Venous Function Tests
Physiologic tests of venous function are important in assessing the cause and severity of venous insufficiency. The physiologic parameters most often measured are the venous refilling time (VRT), the maximum venous outflow (MVO), and the calf muscle pump ejection fraction (MPEF).
Venous refilling time
The VRT is the time necessary for the lower leg to become suffused with blood after the calf muscle pump has emptied the lower leg as thoroughly as possible. When patients with healthy veins are in a sitting position, venous refilling of the lower leg occurs only by means of arterial inflow and requires at least 2 minutes.
In patients with mild and asymptomatic venous insufficiency, some venous refilling occurs by means of reflux across leaky valves. These asymptomatic patients have a VRT of 40-120 seconds.
In patients with significant venous insufficiency, venous refilling occurs through high-volume reflux and is fairly rapid. An abnormally fast VRT of 20-40 seconds is recorded, reflecting retrograde venous flow through failed valves in superficial or perforating veins. This degree of reflux may be associated with the typical symptoms of venous insufficiency. Patients often complain of nocturnal leg cramps, restless legs, leg soreness, burning leg pain, and premature leg fatigue.
A VRT shorter than 20 seconds is markedly abnormal and is attributable to high volumes of retrograde venous flow. High-volume reflux may occur via the superficial veins, the large perforators, or the deep veins. Patients with this degree of reflux are nearly always symptomatic. When the VRT is shorter than 10 seconds, venous ulcerations are so common as to be considered virtually inevitable.
Maximum venous outflow
MVO testing is performed to detect an obstruction to venous outflow from the lower leg, no matter what the cause. Its results are a measure of the speed with which blood can flow out of a maximally congested lower leg when an occluding thigh tourniquet is suddenly removed.
A major advantage of MVO testing is that as a functional rather than anatomic test, it is sensitive to significant intrinsic or extrinsic venous obstruction due to any cause at almost any level. It can be used to detect obstructing thrombus in the calf veins, the iliac veins, and the vena cava, areas where ultrasonography and venography are insensitive. It can also be used to detect venous obstruction due to extravascular hematomas, tumors, and other extrinsic disease processes.
The main disadvantage of MVO testing is that it is sensitive only for significant venous obstruction and not for partial obstruction. It is not useful for the detection of reflux-induced venous insufficiency. A normal MVO result does not absolutely rule out DVT.
Muscle pump ejection fraction
The MPEF test is used to detect failure of the calf muscle pump to expel blood from the lower leg. Its results are highly repeatable, but a skilled operator is required to obtain clean, meaningful tracings.
The patient is asked to stand on his or her tiptoes 10-20 times or to dorsiflex his or her ankle. The change in a physical parameter that reflects the blood volume in the calf is recorded as the calf muscle is pumped.
In patients with normal veins and a normal calf muscle pump, 10-20 tiptoe motions or ankle dorsiflexions empties the venous capacitance circuit of the calf. In patients with muscle pump failure, severe proximal obstruction, or severe deep venous insufficiency, tiptoe motions or ankle dorsiflexions have little or no effect on the amount of blood remaining in the calf. Venous insufficiency due to this cause is difficult to treat
Ambulatory Venous Pressure Monitoring
Ambulatory venous pressure (AVP) monitoring is the criterion standard in assessing the hemodynamics of CVI. This test involves the insertion of a needle connected to a pressure transducer into the dorsal foot vein. It has been shown to be valuable in assessing the severity and clinical outcomes of CVI. Its use is limited given its invasive nature, possible limitations, and potential alternate diagnostic modalities. [21]
-
Superficial venous insufficiency with skin changes.
-
Ulcer due to venous insufficiency.
-
Venous valve. Thrombosis can begin as blood flow becomes turbulent, permitting platelets to remain in valve sinus. This forms nidus of thrombus.
-
Hemodynamic charting of (a) healthy patients, (b) patients with only varicose veins, (c) patients with incompetent perforator veins, and (d) patients with deep and perforator incompetence.
-
Perforator vein bulging into subcutaneous tissue.
-
Chronic venous stasis ulcer.
-
Venous stasis ulcer and surrounding dystrophic tissue.
-
Venous insufficiency iliofemoral obstruction (Palma operation). Saphenous vein from contralateral leg tunneled subcutaneously to femoral vein of affected limb; cumulative patency of 75% at 5 years. Procedure relieves venous claudication but may not heal ulcers or relieve swelling.
-
Lower-leg venous anatomy.
-
Perforating veins of lower leg.
-
Venogram demonstrating incompetent perforating veins.
