Because the course of the vein is drawn upon the skin with indelible marker and then stain, the unprotected probe head may become permanently stained, especially through the relatively porous probe membrane. In order to avoid this, the probe is covered with a probe cover or even a plastic sandwich bag containing ultrasound gel. The medium between the probe and skin must be aqueous and not air.

Preparation of the examination area or room is of vital importance for successful mapping. The room should be well heated in order to minimize peripheral venoconstriction. For the same reason, the patient should remain clothed and/or covered, exposing only the necessary limb. Sometimes keeping the exposed foot covered is also useful. Finally, the room is generally kept dark in order to assist with visualization of the ultrasound image on the display.

Positioning for imaging of the great saphenous vein usually requires the stretcher to be placed in reverse Trendelenburg with the knee slightly flexed and the hip externally rotated. Standing the patient is usually not necessary for the majority of cases and is certainly not well tolerated by many in this patient group. Occasionally, the patient may be stood at the end of the procedure to check the vein size under maximal pressure. In the past, tourniquets were employed in an effort to maximally dilate these veins, but this has proven to be poorly tolerated by the patients and has therefore been abandoned.

Imaging of the saphenous vein can be started at either one of three logical sites: the ankle, the knee, or the groin . Generally, the groin is favored as the saphenofemoral junction can usually be positively identified with its characteristic relationship to the common femoral vein and artery (“Mickey Mouse ,” Fig. 47.2). In very obese patients, however, this may be difficult to image even with the lower-frequency transducers. Beginning imaging at the knee may avoid some of the above problems, but it is much easier to follow the wrong vein or to miss double systems.

The scanning technique is very different from that used with arterial imaging. Because these veins are superficial and have very little internal pressure, they are exquisitely sensitive to external pressure such as from the probe itself. Therefore, the weight of the probe and the examiner’s hand should be supported by the fourth and fifth fingers offset from the course of the vein. The examiner can check his or her technique by examining the vein in cross section: it should be round, not elliptical (Fig. 47.3).

Held in this way, the probe is applied at or near the groin in a transverse plane. Staying in this plane, the probe may be moved in a medial-lateral direction until the vein is visualized. Generally, the vein runs slightly medial to the midline of the thigh at this point. The vein may be followed into the saphenofemoral junction to confirm its identity. The vein may be compressed to ensure patency. If this is in doubt, pulsed Doppler may be used in conjunction with manual compression of the distal leg.

Care should be taken to keep the probe as perpendicular to the skin as possible in order to help the surgeon make his incisions directly over the vein. This is entirely possible in most cases where the leg is normal but can be unavoidably inaccurate if the skin is sagging or otherwise redundant. Correct marking of the course of the vein on the skin requires some experience and constant feedback from operating room findings.

Once the vein is identified in the transverse plane, the probe is slowly rotated 90 degrees to insonate the vein in a longitudinal plane. The position of the vein may then be marked at either end of the probe. We use a Sharpie King Size Permanent Marker with a chisel tip because it will mark through gel (and it will stay wet when left uncapped). As the probe is moved distally, a new dot is made every inch or so. After the remainder of the scan is completed, the dots are painted over with a continuous line. We use carbol fuchsin stain (originally obtained from the radiation oncology department) applied with a cotton-tip applicator. This provides the operator with a map of the underlying vein (Fig. 47.4). This map should provide the surgeon with a detailed picture of the vein, but it does not necessarily precisely indicate the best place for the surgeon to place the incisions; this requires some judgment from the surgeon in addition to the external map.

The size of the vein can also be measured. This is best done with the vein imaged in the transverse plane. Usually, the vein size is determined in the groin, the distal thigh, and three equidistant points along the lower leg. Any marked changes in vein diameter along the course of the vein should also be marked. The limitations of these measurements should be stressed. Because they are obtained with the vein under venous pressure, they generally underestimate the diameter of the vein when the vein is connected to arterial pressure. In addition, these measurements are taken of the inside diameter of the vein, not the outside diameter. The surgeon should regard these measurements as the minimum size of the available vein. It is very important that the surgeon does not abandon the thought of using the vein without visually inspecting the vein at the time of operation. The vein by ultrasound may appear quite small and actually be quite acceptable upon arterialization. The vein size is roughly underestimated by a millimeter or more by ultrasonography under venous pressure.

As the probe is moved from the groin to the ankle, the vein is held in a longitudinal plane. As marks are made on the skin, the probe is rotated to a transverse plane every 3–4 inches at which time the vein may be compressed to confirm patency and its diameter measured and recorded. Other data that should be generally noted include the relationship of the vein to the superficial and deep fascia and the relative depth of the vein in regard to the skin. It does help if the ultrasonographer has some direct experience with the relationship of the saphenous vein to the fascia. Knowing that the main vein usually runs deep to the saphenous fascia, for instance, allows for the ultrasonographer to avoid tracking more superficial subcutaneous veins which may be as large or larger [9]. This is especially the case when the patient has large varicosities of the thigh where selecting the proper vein to track and follow is largely a matter of identifying the vein with the proper relationship to the saphenous compartment.

Other more subtle but no less important data that may be obtained include information about the vein wall. Normally, the intimal-medial complex appears as a thin, single, well-delineated reflection. With the probe in the longitudinal plane, an abnormal appearance of the vein wall should be noted (Fig. 47.5). This may be expressed in the report by describing the vein wall as being thickened (worrisome), calcified (worrisome but often usable), irregular (very worrisome, with possible recanalization), or sclerotic (almost certainly not usable). These notations are somewhat subjective and really describe a whole class of vein wall abnormalities but are of paramount importance to the surgeon as it allows for some preoperative planning to avoid using these diseased veins whenever possible.

Patients in this group may have variable amounts of peripheral edema. This complicates imaging considerably as the layers of the edematous tissue may appear similar to a vein by ultrasound. This is the one condition in which the use of color flow imaging is useful; distal compression will help define the vein from the surrounding fluid-filled tissue planes especially with color flow imaging.

At this point, the entire vein should have been completed in the first pass from the groin to the ankle. There should be a line of black dots along the course of the vein. The vein is rescanned from the top down but with the probe held in the transverse plane. During this pass, major branches are noted and marked. This includes known named tributaries such as the posterior (medial) and anterior (lateral) accessory saphenous veins in the upper thigh as well as major perforators, which are seen as posterior or posterolateral branches that dive through the deep fascia to communicate with the deep venous system (Fig. 47.6). Preoperative identification of these points will allow the surgeon to gain access to the vein with a minimum amount of dissection and to ligate these perforators efficiently.

After the main branches are marked, the scan may be completed by connecting the dots with the carbol fuchsin stain, leaving the surgeon a cutaneous map upon which the operation may be planned. In addition, a form depicting the leg (or arm) being mapped is filled out. This form has a diagram of the mapped vein and notation for abnormalities, configuration, vein size, depth, and any other data felt to be useful to the operator. This entire procedure may take as little as 15 min with a single simple system, although longer periods of time are required for more complicated cases [10].