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Chap-12.qxd 29~8~04 14:52 Page 173
ANATOMY OF THE LOWER LIMB VENOUS SYSTEM AND ASSESSMENT OF VENOUS INSUFFICIENCY
spontaneous phasic flow pattern in the superficial femoral and common femoral veins. If the sapheno- femoral junction is incompetent, venous back- pressure will produce significant reflux across the junction (Fig. 12.13). One potential pitfall of using the Valsalva maneuver for the assessment of proximal reflux can occur in patients who have a competent valve in the iliac vein system, which is
REFLUX
Figure 12.13 Incompetence of the saphenofemoral junction is demonstrated by a large volume of reflux during a Valsalva maneuver (the arrow indicates the start of Valsalva).
S
AB
Figure 12.14 A: In this color flow image of the saphenopopliteal junction, flow in the SSV (S) and popliteal vein (coded blue) is toward the heart during distal augmentation. B: Following squeeze release there is significant retrograde flow (coded red) in the SSV and popliteal vein above the junction, due to saphenopopliteal junction incompetence. However, no retrograde flow is demonstrated in the popliteal vein below the level of the saphenopopliteal junction, indicating popliteal vein competency at this level (arrow).
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usually valve-free. In this situation, the proximal valve will protect an incompetent saphenofemoral junction or proximal superficial femoral vein, and no reflux will be seen. The Valsalva maneuver is not used for the assessment of more distal veins.
GRADING OF SUPERFICIAL AND DEEP
VENOUS REFLUX
Considerable debate surrounds the grading of venous reflux, especially as different patterns of reflux can be observed in the venous system. The following proto- col is used by our unit. With the relevant segment of vein imaged in longitudinal section, the color box is steered to obtain the best angle of insonation to the vein. A calf squeeze is performed and the augmenta- tion of flow demonstrated with color flow imaging. It is often possible to tell from the color flow display if the vein is normal or incompetent. A competent vein will display a burst of flow toward the heart dur- ing a calf squeeze, followed by an abrupt cessation of flow during squeeze release, although a very brief period of retrograde flow may be seen as the valves close. Significant venous reflux will be demonstrated by a sustained period of retrograde flow following calf release (Figs 12.14 and 12.15). However, the