Page 190 - Libro vascular I

Chap-12.qxd 29~8~04 14:52 Page 181
ANATOMY OF THE LOWER LIMB VENOUS SYSTEM AND ASSESSMENT OF VENOUS INSUFFICIENCY
may be from the internal iliac vein distribution. The Giacomini vein tends to run in a layer of fascia, which can aid its identification. It is possible to misidentify very superficial posterior thigh branches of the LSV as the Giacomini vein.
4. In transverse section, the SSV is followed distally from the popliteal fossa along the posterior aspect of the calf, where it runs toward the posterolateral aspect of the ankle. The SSV is then assessed for reflux along its length in longitudinal section. However, sometimes the vein is so small that it is difficult to demonstrate flow during compres- sion. Large perforators can be assessed for com- petency. It is sometimes possible to see varicose branches from the LSV interconnecting to the SSV system. Conversely, medial varicose branches of the SSV may also interconnect to the LSV system (Fig. 12.22). The SSV can also supply varicose areas on the lateral and anterior aspects of the calf via branches.
5. The origin of the saphenopopliteal junction is sometimes marked preoperatively with the aid of duplex scanning, owing to its highly variable position. Some surgeons ask for a mark to be made on the skin corresponding to the position of the junction. However, others prefer a mark over the SSV just distal to the junction, so that the vein can be identified and followed back to the junction. Alternatively, a cross can be placed over the junction with a line drawn indicating the path of the SSV to the point where it becomes superficial. It is important for the sur- geon and sonographer to agree on a system of marking to avoid any misunderstandings.
Concluding the scan
In some circumstances, the varicose veins may lie in more unusual distributions, such as the anterior aspect of the calf or lateral aspect of the thigh. In these situations, it is important to follow the varicose areas proximally in transverse section to identify the supply. The supply is frequently from varicose branches of the LSV or SSV, depending on the location of the vari- cose areas. One such example is incompetence of the anterolateral vein from the saphenofemoral junction. This vein often supplies varicose areas on the anterior aspect of the thigh and lateral calf. The main proximal trunk of the LSV can be competent or incompetent
in this situation. In certain circumstances, varicose veins running along the lateral aspect of the thigh and calf can be related to isolated perforators located on the lateral aspect of the upper thigh. Varicose veins in the lower posterior and posteromedial thigh can be supplied by the Giacomini vein. In this unusual situa- tion, blood flows in a loop, across an incompetent saphenopopliteal junction and up the Giacomini vein, which then feeds the superficial varicosities running down the leg. This is a ‘paradoxical’ situation, in which the thigh veins are filled by ‘antigravitational’ flow, but in fact the flow will eventually make its way down into the calf via the incompetent veins, in the correct gravitational direction (Georgiev et al 2003). The main trunk of the SSV can be competent or incompetent in this situation. In some patients, it may be impossible to clearly define the source of the vari- cose veins, especially if they are very small, are dif- fusely distributed and generally run into very small superficial tributaries.
B-mode appearance of varicose veins
and perforators
Varicose veins are relatively easy to identify on the B-mode image. They appear as single or multiple dilated tortuous vessels that vary randomly in diameter as the probe is swept across the varicose area (Fig. 12.27). They are superficial and may be located in the thigh as well as the calf. The main trunk supplying varicose areas, such as the LSV in the thigh, may be dilated but often has a reason- ably even caliber and is frequently not visible on
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Figure 12.27
varicose veins.
A transverse image of tortuous dilated