Page 251 - Libro 2

15
Duplex Imaging of the Upper Extremity Venous System
Steven R. Talbot and Mark Oliver
OBJECTIVES
KEY TERMS
acute thrombus | chronic thrombus | deep vein | superficial vein | valve
GLOSSARY
acute thrombus newly formed clotted blood within a vein, generally less than 14 days old
chronic thrombus clotted blood within a vein that has generally been present for a period of several weeks or months
deep vein a vein that is the companion vessel
to an artery and travels within the deep muscular compartments of the leg or arm
This chapter will discuss the venous duplex ultra- sound examination of the upper extremity. The pro- tocol techniques used in the upper extremity are similar to those discussed for the lower extremity in Chapter 14. However, there are three major differ- ences to consider when moving from imaging legs to imaging the upper extremity. They are:
1. Many thrombi in the lower extremity are caused by stasis (the patient not moving). This is not true in the upper extremity. The arms do not have a counterpart to the soleal sinus veins of the legs so there is no similar place for a thrombus to spontaneously form in the arms. This is why, until modern times, thrombi in the upper extremity veins were rare. The following section on pathophysiology will discuss this further.
2. The superficial veins are affected more in the arms than in the legs. Additionally, a thrombus
superficial vein a vein that is superior to the muscular compartments of the leg or arm; travels within superficial fascia compartments; has no corresponding companion artery
valve an inward projection of the intimal layer of a vein wall producing two semilunar leaflets that present the retrograde movement of blood flow
in a superficial vein in the arms may have greater clinical significance because superficial veins in the arms are commonly larger than their deeper counterparts. For instance, the basilic vein (a superficial vein) may be sev- eral times larger than the radial vein (a deep vein). Thus, a thrombus in the basilic vein may require treatment, whereas a thrombus in the radial vein may not. Veins like the axillary and subclavian, however, are large deep veins where a thrombus within them is more aggres- sively treated than a thrombus in the superfi- cial veins.
3. Veins in the legs follow pretty reliable courses. The venous anatomy in the upper extremity can be more variable. Most of this variation occurs around the median cubital vein and how it connects with the basilic and cephalic veins.
Describe the components of the upper extremity venous system
Define the normal image and Doppler characteristics of the venous system
Identify the image characteristics consistent with acute and chronic thrombus
Describe the Doppler waveform characteristics associated with various pathologies
List the risk factors associated with venous thrombosis in the upper extremity
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