At the completion of this course the participant will be able to:
• Describe the normal anatomical features of the great saphenous vein, small saphenous vein, cephalic vein and basilic vein.
• Identify pathology observed within the superficial veins
• Describe the basic techniques of venous mapping
• Identify limitations encountered during vein mapping
• Describe diagnostic ultrasound criteria utilized in venous mapping
Ann Marie Kupinski, PhD RVT RDMS
Professor of Radiology, Albany Medical College, Albany NY
North Country Vascular Diagnostics, Inc, Altamont NY
The Institute for Advanced Medical Education is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.
The Institute for Advanced Medical Education designates this enduring material for a maximum of 2.0 AMA PRA Category 1 Credits™. Physicians should only claim credit commensurate with the extent of their participation in the activity.
This activity qualifies as SA-CME credits for those physicians who must complete Self Assessment Modules in fulfillment of their specialty board credentialing.
These credits are accepted by the American Registry for Diagnostic Medical Sonography (ARDMS).
For further information on applicability and acceptance of continuing education credit for this activity, please consult your professional licensing board or other credentialing organization.
Physicians, sonographers and others who perform and/or interpret vascular ultrasound.
This activity is designed to be completed within the time designated. To
successfully earn credit, participants must complete the activity during the
valid credit period. To receive AMA PRA Category 1 Credit™, you must receive a minimum score of 70% on the post-test.
Follow these steps to earn CME credit:
Estimated Time for Completion: approximately 2 hours
Date of Release and Review: November 21, 2016
Expiration Date: November 20, 2019
In compliance with the Essentials and Standards of the ACCME, all individuals in control of the content of this CME tutorial are required to disclose any significant financial or other relationships they may have with commercial interests.
Ann Marie Kupinski, PhD RVT RDMS discloses no such relationships exist.
No one at IAME who had control over the planning or content of this activity
has relationships with commercial interests.
SUPERFICIAL VENOUS ANATOMY
The Great Saphenous Vein
Figure 2 illustrates common configurations of the thigh portion of the great saphenous vein. In about 60% of cases, the great saphenous vein is a single medial trunk in the thigh, curving slightly toward the inner thigh. Less frequently in only 8% of cases there is a single dominant system in the thigh that courses laterally. It is thought that this lateral version is more likely the anterior accessory saphenous vein which has become the dominant outflow track in these instances. Remaining configurations of the great saphenous vein all include various interconnections with tributaries. Some of the larger tributaries appear to create a double saphenous system or a partial closed loop. The major tributaries of the great saphenous vein include the anterior and posterior accessory saphenous veins.
It is very important to identify the various veins that are present. Surgeons can select the most appropriate vein based on the planned procedure. If a short segment of vein is needed, a tributary or accessory saphenous vein may be used, thus maintaining the main trunk of the great saphenous for use if needed at a later date.
The great saphenous vein in the calf is less variable and in two-thirds of cases is a single dominant system coursing anteriorly near the medial border of the tibia (Figure 3). The posterior accessory saphenous vein discussed in the preceding section is also present in the calf. It typically has a smaller diameter as compared to the main trunk of the saphenous vein and is not suitable for use as a bypass conduit. In about 7% of patients, the posterior accessory saphenous vein is dominant over the more anterior system of the calf.
When using the vein as a conduit for a lower extremity bypass, the locations of the perforating veins should be identified. Perforating veins connect the superficial venous system to the deep venous system (Figure 4). They have valves to insure the one-way direction of blood flow from the superficial to the deep. If the vein is used insitu for a bypass and a perforating vein is left intact, blood flow will be shunted away from the distal bypass to the deep venous system thus creating an arteriovenous fistula. This arteriovenous fistula will steal blood from the distal arterial bed and will need to be ligated in order to maintain adequate flow through a bypass. Marking the locations of perforating veins during the preoperative mapping procedure will alert the surgeon to allow for ligation of the perforators prior to the completion of the bypass surgery.
Another source of conduit is the small saphenous vein. It can be used for lower extremity arterial bypass procedures and rarely for coronary artery bypassgrafts. The small saphenous vein begins at the junction of two small veins which leave the foot and travel medially and laterally adjacent to the Achilles tendon. The small saphenous vein courses as a single trunk approximately at the middle of the posterior aspect of the calf. It terminates at the popliteal fossa into the popliteal vein. In approximately 20% of limbs, the small saphenous vein extends above the popliteal fossa. This portion of the vein is referred to as the cranial extension of the small saphenous vein. This cranial extension can terminate directly into the femoral vein, or into the inferior gluteal vein or may communicate into the great saphenous vein. This cranial extension of the small saphenous vein is important when a patient may be vein limited and a long length of vein is needed as a conduit.
The Small Saphenous Vein
The Cephalic and Basilic VeinsVenous mapping techniques includes the evaluation of the superficial veins of the arm. It is the standard of care to assess these veins in patients undergoing the creation of a dialysis access fistula. The cephalic vein begins at the level of the wrist, continuing along the radius in the forearm, through the upper arm, terminating into the subclavian vein. The basilic vein also begins at the level of the wrist, coursing along the ulnar aspect of the forearm. The basilic vein continues into the upper arm where it joins the brachial veins to form the axillary vein. The termination of the basilic vein can vary and in about one-third of patients the basilic vein terminates in the mid or lower portion of the upper arm rather than closer to the axilla. The cephalic and basilic veins communicate at the antecubital fossa via the medial cubital vein. The patterns of the venous segments at the antecubital fossa and the position of the medial cubital vein can display variability.
Rarely is it necessary for the patient to stand in order to adequately visualize and measure the superficial veins of the leg. The arm veins can be examined with patient’s arm extended out to the side and slightly lower than the chest level (Figure 7). Tourniquets can be used to aid in dilating the veins. However, they are not required and often produce too much patient discomfort.
Given the superficial veins are under low venous pressure, light transducer pressure should be used. Using a transverse orientation, the great saphenous vein is identified at the saphenofemoral junction (Figure 8).
Saphenous vein diameter is measured at multiple levels including the saphenofemoral junction, proximal, mid and distal thigh, knee and proximal, mid and distal calf. If multiple systems exist, each should be measured to determine system dominance. The diameter is measured by the placing calipers perpendicular to each other at the outer to outer walls (Figure 12).
Once the course of the vein has been marked, the tributaries have been noted and the vein diameters measured, the ultrasound gel can be wiped off the limb. Liquid marking ink (such as a carbol fuchsin stain used in radiation therapy) can be applied with a cotton-tipped applicator or a permanent marker can be used. The dashed marks originally placed are connected to map the course of the vein (Figure 13). This skin marking will remain on the skin for varying lengths of time depending on the type of permanent ink used. In most patients, the marks will be visible for at least 3-5 days. In addition, a hard copy drawing is recorded for the patient’s chart.
The scanning techniques described for the great saphenous vein can be used to map the small saphenous, cephalic and basilic veins. The small saphenous vein is first identified at its confluence with the popliteal vein then followed distally through the calf (Figure 14). The small saphenous vein diameters are recorded in the proximal, mid and distal calf. Figure 15 illustrates a completed small saphenous vein mapping.
Mapping of the basilic vein is performed by following the vein along the ulnar aspect of the forearm to its termination into the axillary vein. The cephalic vein can be followed from the radial aspect of the forearm to the upper arm. In the upper arm if courses over the biceps muscle, across the shoulder terminating into the subclavian vein. In patients getting vein mapping prior to creation of hemodialysis access fistulae, the position of the medial cubital vein as it relates to the cephalic and basilic veins is mapped. The vein diameters are measured proximally and distally in the forearm and upper arm. Figure 16 illustrates a completed arm vein mapping.
Vein mapping must determine much more than the presence of absence of a vein. It must also determine the suitability of that vein for use as a bypass conduit. A normal healthy vein should have smooth, thin walls (Figure 17). The vein should be compliant and easily compress with minimal transducer pressure. Valve sinuses may appear elliptical but in some smaller veins they may be difficult to identify. If valve leaflets are visualized, they should be freely moving without any evidence of thrombus behind the leaflets.
The planar arrangement of the veins should be observed during the mapping procedure and noted on the written report. This is of particular importance with mapping the great and small saphenous vein as the depth of these vessels will vary. Figure 18 illustrates the normal orientation of the main trunk of the great saphenous vein within the saphenous compartment bounded by the saphenous fascia superficially and deeply by the muscular fascia. These layers of fascia produce the appearance of what some people refer to as the Egyptian eye appearance of the vein.
When double systems exist, often the veins travel in different anatomic planes through the thigh as shown in Figure 19. The dominant vein may not be the most superficial system or not be within the saphenous compartment. This information is important to the surgeon so that the best vein is selected. When double systems exist, often the veins travel in different anatomic planes through the thigh as shown in Figure 19. The dominant vein may not be the most superficial system or not be within the saphenous compartment. This information is important to the surgeon so that the best vein is selected.
Laboratory criteria for suitable vein diameters vary based on surgeon preference and the procedure performed. A cardiothoracic surgeon may prefer a certain diameter vein for a coronary bypass while a general surgeon may have different diameter criteria for a dialysis fistula. Most surgeons will not use a vein which is less than 2.0 mm in diameter.
Various abnormalities can be observed within the superficial veins. Isolated segments of partial thrombus may be encountered during vein mapping (Figure 20). Thrombus will vary in echogenicity with an anechoic or hypoechoic appearance being more likely associated with acute thrombus. Chronic or residual thrombus may be hyperechoic but this is less reliable. Completely thrombosed veins will be noncompressible, lack any color filling and not demonstrate a Doppler signal. With partially thrombosed veins, the walls may slightly compress together under transducer pressure but not completely coapt. Color flow imaging will demonstrate a reduced flow lumen. Doppler signals obtained from partially thrombosed veins will display a decrease in phasicity.
An irregular intimal surface or wall thickening may indicate evidence of recanalization (Figure 22). These veins are not usually considered to be adequate conduit for arterial bypasses. Occasionally calcification can be observed in the absence of any other abnormality. Bright echoes within the vein wall producing acoustic shadowing is the classic ultrasound appearance of calcification (Figure 23). Isolated areas may not preclude the entire vein from being used as a conduit. The surgeon may simply use non-calcified segments. However, diffuse intermittent calcification renders the vein inadequate for bypass material. Venous calcification can be often observed in diabetic patients. Lastly, another pathology that can be noted on the image is a stenotic or frozen valve (Figure 24). This may be encountered in a vein that was previously thrombosed.