Deep venous system

The anatomy of the deep veins is shown in Figure 13.2. Generally, the deep veins are larger than their corresponding artery. The main deep veins of the thigh and calf are the following:

Figure 13.2 Anatomy of the deep venous system, including the iliac veins and vena cava (A and B).

The posterior tibial and peroneal veins are usually paired and are associated with their respective arteries. The paired veins join into common trunks in the upper calf before forming the below-knee popliteal vein. The soleal veins are deep venous sinuses and veins of the soleus muscle that drain into the popliteal vein. They are an important part of the calf muscle pump mechanism (see Ch. 5). The gastrocnemius veins drain the medial and lateral gastrocnemius muscles. The gastrocnemius veins normally drain into the popliteal vein through single or multiple trunks below the level of the saphenopopliteal junction. The anterior tibial vein is paired and associated with the anterior tibial artery and drains to the popliteal vein. The above-knee popliteal vein runs through the adductor canal and becomes the femoral vein in the lower medial aspect of the thigh. The femoral vein runs toward the groin, where it is joined by the deep femoral vein to form the common femoral vein. This confluence is distal to the level of the saphenofemoral junction (SFJ) and common femoral artery bifurcation (see Fig. 9.8). The common femoral vein lies medial to the artery, becoming the external iliac vein above the inguinal ligament (Fig. 13.2). The external iliac vein runs deep and is joined by the internal iliac vein, which drains blood from the pelvis, forming the common iliac vein. The left common iliac vein runs deep to the right common iliac artery to drain into the vena cava, which lies to the right of the aorta.

Superficial venous system

The main superficial veins are the great saphenous vein (GSV) and small saphenous vein (SSV) (Fig. 13.3) (often referred to as the long saphenous vein [LSV] and short saphenous vein, respectively). The GSV and SSV are contained in a separate saphenous compartment, bounded superficially by the hyperechoic saphenous fascia and deeply by the muscular fascia (Fig. 13.4). Branches, tributaries, and cross-communicating veins lie external to the saphenous compartment (Caggiati et al. 2002) (Fig. 13.1). The saphenous compartment resembles the shape of an Egyptian eye when imaged.

Figure 13.3 Anatomy of the superficial veins, including the position of commonly located perforators. (A) The great saphenous vein. Posterior tibial perforators (sometimes referred to as Cockett’s perforators) are located at distances of approximately 6, 13, and 18 cm above the medial malleolus. Paratibial or Boyd perforators are located in the upper calf, approximately 10 cm below the knee joint. (B) The small saphenous vein.

Figure 13.4 The main trunks of the superficial veins are shown in cross-section. (A) The great saphenous vein (V) lies in the saphenous compartment, bounded by the deep muscular fascia (upward arrow) and the saphenous fascia (downward arrow). Note a superficial tributary (T) and some varicose veins (VV) lying above the saphenous compartment. (B) The small saphenous vein (V) is also bounded by the deep fascia (upward arrow) and saphenous fascia (downward arrow). The medial gastrocnemius muscle (MG) and lateral gastrocnemius muscle (LG) are shown on this image of the right leg.

The GSV and saphenofemoral junction

The anatomy of the GSV is shown in Figure 13.3A. The distal GSV is located anterior to the medial malleolus (inner ankle bone), runs up the medial aspect of the calf and thigh, and is joined by a number of superficial tributaries. The GSV drains into the common femoral vein approximately 2.5 cm below the inguinal ligament at the SFJ. It is important to have a detailed understanding of the anatomy in this area, as there are at least six other tributaries draining to the GSV at the level of the SFJ (Fig. 13.5). These tributaries can be the source of primary or recurrent varicose veins. It is not usually possible to identify all of these tributaries by ultrasound. The anterior accessory saphenous vein (AASV), sometimes called the anterolateral thigh vein, drains flow from the anterior and lateral aspect of the knee and lower thigh and runs across the anterior aspect of the thigh into the SFJ (Fig. 13.3). However, it can sometimes join the GSV at a variable level below the junction. The AASV is usually easy to identify with ultrasound and it is contained within its own fascial compartment (Figs 13.6 and 13.7). In the upper thigh, it runs in the same line as the femoral vein: this is referred to as the alignment sign and helps to distinguish the AASV from the GSV that lies medial and posterior to the AASV (Fig. 13.7). The posterior accessory saphenous vein also runs in a facial compartment and drains flow from the posteromedial and posterior regions of the lower thigh and usually joins the main trunk of the GSV in the upper thigh. There are sometimes connections between the thigh extension (TE) of the SSV or Giacomini vein, described later in the chapter.

Figure 13.5 The anatomy of the saphenofemoral junction.

Figure 13.6 A diagrammatic representation of the saphenous compartments containing the great saphenous vein (GSV) and anterior accessory saphenous vein (AASV). In this example a large incompetent tributary inserts to an incompetent GSV in the mid-thigh (A), with the GSV becoming small and competent beyond this point. The tributary communicates with the main trunk lower in the thigh (B), where the GSV becomes incompetent once more. Alternatively, the large tributary could continue to run down the leg (indicated by the short dashed lines) and the GSV could remain small below point B. There can be many anatomical variations involving the GSV and its tributaries, especially in the knee region and mid to lower thigh. FV, femoral vein.

Figure 13.7 A transverse panoramic view of the right upper thigh showing the anterior accessory saphenous vein (AASV: straight arrow) lying above the femoral vein (FV), indicating the alignment sign. The great saphenous vein (curved arrow) is lying medially in its own saphenous compartment. In this example it is likely that the AASV is incompetent due to its size.

The SSV, saphenopopliteal junction, and Giacomini vein

The anatomy of the SSV is shown in Figure 13.3B.

The distal SSV arises posterior to the outer aspect of the ankle (lateral malleolus) and runs up the posterior calf in an interfascial compartment (Fig. 13.4B). In the upper calf the compartment appears as a triangular shape that is defined by the lateral and medial heads of the gastrocnemius muscle and the superficial fascia that streches over the intermuscular groove (Cavezzi et al. 2006). It drains to the popliteal vein via the saphenopopliteal junction located superior to the insertion of the gastrocnemius vein. Typically the saphenopopliteal junction is located 2−5 cm above the popliteal knee crease. However, the anatomy can be extremely variable. The saphenopopliteal junction may be located proximal to the popliteal fossa, draining to the above-knee popliteal vein or distal femoral vein (Fig. 13.8). The SSV can insert directly into the gastrocnemius vein or share a common confluence (Fig. 13.8). In addition, it is common to find a TE of the SSV, described by Giacomini in 1873 running in an intrafascial compartment or groove bounded by the semitendinous muscle, long head of biceps, and superficial fascia (Georgiev et al. 2003).

Figure 13.8 The level of the small saphenous vein (SSV) insertion can be highly variable. Potential positions are shown by numbers and lettered diagrams. The SSV normally drains to the popliteal vein (P) in the popliteal fossa at the saphenopopliteal junction (diagram A). It can share a common trunk (CT) with the gastrocnemius vein (GV) (diagram B). It can share a common junction with the gastrocnemius vein (diagram C). It sometimes has a high junction with the popliteal vein (blue dashed line). The thigh extension vein, when present, runs above the level of the saphenopopliteal junction and has a variable outflow. It may drain to the femoral vein, profunda femoris vein or branches of the internal iliac vein (green lines). It may also drain to the great saphenous vein (GSV) and in this situation the vein is termed the Giacomini vein (orange line). Note that it is possible to confuse the posteromedial tributary of the great saphenous vein with the Giacomini vein; see text.

There are a number of terminations for the TE, as shown in Figure 13.8. The TE is often referred to as the Giacomini vein, although strictly this term should only be applied when the vein connects to the GSV. There is sometimes confusion as to whether a posterior thigh vein is the Giacomini vein or merely a superficial posteromedial tributary of the GSV. Generally, the Giacomini vein should appear to run into an intrafascial compartment in the lower thigh before joining the SSV, whereas superficial tributaries of the GSV tend to lie above the superficial fascia. Finally, there are usually intersaphenous veins in the upper calf, running between the GSV and SSV.

Perforators

There are major perforating veins in the GSV and SSV system and these can be variable in their presence, being more numerous below the knee (Fig. 13.3). Large perforators are easy to identify by ultrasound. It is worth noting that some perforators do not connect directly to the main trunks of the GSV or SSV, but communicate via side branches of the main trunks. There are a number of perforating veins associated with the SSV, especially from medial and lateral gastrocnemius veins and soleal veins.

Other superficial veins

There is typically a lateral venous system in the leg but the veins are often very small and difficult to detect. They may represent an embryonic system and are only relevant if there are isolated varicose veins in this area not associated with the GSV or SSV.

Anatomical variations

There are numerous anatomical variations in the lower-limb venous system, and even experienced sonographers will encounter new variations from time to time. Duplicated, or bifid, vein systems are relatively common and mainly involve the femoral vein and popliteal vein (Fig. 13.9). A potentially confusing anatomical variation occurs in patients who have a large deep femoral vein in the thigh running as a large trunk between the popliteal vein and the common femoral vein. In this situation, the size of the femoral vein in the thigh can be small when compared with the size of the superficial femoral artery, and this appearance may be mistaken for evidence of venous obstruction. However, good flow augmentation, with a calf squeeze, will be demonstrated in the common femoral vein just below the SFJ. Careful inspection by duplex will normally reveal the larger deep femoral vein. A low-frequency 2–4 MHz curved linear array transducer may be necessary to identify this vein. A very rare anomaly can occur toward the level of the SFJ, with the GSV running between the superficial femoral artery and profunda femoris artery to drain into the SFJ.

Figure 13.9 A transverse image of a duplicated or bifid femoral vein with the artery (A) lying between the paired veins (V).

Venous valves

Veins contain bicuspid, valves to prevent the reflux of blood to the extremities. There is often a characteristic dilation of the vein at the valve site that can sometimes be seen on the ultrasound image (Fig. 13.10). Venous valves are able to withstand high degrees of back pressure, typically in excess of 250–300 mmHg. The number of valves in each venous segment varies among individuals, but there are more valves in the distal veins than in the proximal veins, as they have to withstand higher hydrostatic pressures. The inferior vena cava and common iliac vein have no valves, and the majority of the population have no valves in the external iliac or common femoral vein. There is usually a valve at the proximal end of the femoral vein and an average of three to four valves along the length of the femoral and popliteal vein to the level of the knee, although the number can be inconsistent. In most people there is a valve in the below-knee popliteal vein that is sometimes referred to as the ‘gatekeeper,’ as it prevents venous reflux into the proximal calf. The deep veins in the calf contain numerous valves. The GSV and SSV contain approximately 8–10 valves along their main trunks (Browse et al. 1999).

Figure 13.10 An image of a venous valve site in the popliteal vein just below the gastrocnemius vein. (A) The valve is closed. (B) The valve is open.

The configuration of the valves at the SFJ is important to consider as there is typically a terminal valve located at the junction and a preterminal valve that is positioned in the GSV, 3–5 cm distal to the terminal valve. Tributaries of the SFJ join between these two points (Fig. 13.11). This explains how it is possible for the junction to be competent but for reflux to occur across the preterminal valve into the proximal GSV due to flow from the tributaries (Caggiati et al. 2004) (Fig. 13.11A). A similar pattern can exist in the SSV. In addition, there are normally valves protecting many perforating veins so that flow is directed from the superficial venous system to the deep system. In very rare cases, patients may have absent venous valves due to congenital valve aplasia (Eifert et al. 2000). This can be the cause of deep venous reflux in the very young patient.

Figure 13.11 Examples of the saphenofemoral junction (SFJ) and proximal great saphenous vein (GSV) to indicate valve positions. (A) The diagram shows the position of the terminal and preterminal valves. The arrows indicate venous reflux across an incompetent preterminal valve via flow from the tributaries. The terminal valve is competent. (B) An ultrasound example, showing the position of the terminal valve (straight arrow) and preterminal valve (curved arrow) in an incompetent GSV. Two tributaries are shown (T), with one demonstrating marked dilation.

Flow patterns in the venous system

The flow patterns in normal deep veins are described in Chapter 5. The venous flow patterns in the superficial veins can vary, depending on patient position and external factors, such as ambient temperature. Normally there should be no, or very little, spontaneous flow in the GSV and SSV when the patient is standing or sitting. If the ambient temperature in the room is high, vasodilation may result in increased flow in the superficial veins. Evidence of high-volume spontaneous or continuous flow in the superficial veins at rest should be treated with suspicion, as this may indicate obstruction of the deep veins or could be due to infection, such as cellulitis (Fig. 13.12).

Figure 13.12 High-volume spontaneous flow is demonstrated in the great saphenous vein (GSV) of a patient with popliteal and femoral vein obstruction due to chronic postthrombotic syndrome. (A) Spectral Doppler recording from the GSV shown in (B) indicating spontaneous flow. (B) A large dilated GSV. (C) The deep femoral vein (DF) is patent but the femoral vein (arrow) is small. (D) An image of the femoral vessels in the mid-thigh demonstrating small collateral veins (blue) adjacent to the artery (A).

Classification of chronic venous disorders

The CEAP (Clinical−Etiology−Anatomy−Pathophysiology) classification system for venous disorders was developed by an ad hoc committee of the venous forum (Eklöf et al. 2004). It has been developed to facilitate the use of consistent terminology and diagnosis within the clinical and scientific community. The clinical classes are shown in Table 13.1. Therefore, a patient with a painful venous ulcer due to primary venous disease that included great saphenous and popliteal vein reflux, with perforating vein reflux in the calf would have a basic CEAP classification of C_6,s,E_p,A_spd,P_r. In advance CEAP, the classification would be C_2,6,s,E_p,A_s,p,d,P_r2,3,18,14.

Table 13.1 CEAP (Clinical–Etiology–Anatomy–Pathophysiology) classification

Varicose veins

The cause of varicose veins is uncertain, but there is evidence that increased age, female gender, and pregnancy are risk factors (Callam 1994).

Varicose veins appear as dilated, tortuous, elongated vessels on the skin surface, especially in the calf. Abnormal superficial veins can be classified according to their size. Minor cosmetic or intradermal spider veins (telangiectasia) <1 mm in diameter are not visible by ultrasound. Small dilated subdermal veins (reticular veins) 1–2 mm in diameter can also be difficult to image without high-frequency probes. Varicose veins, typically subcutaneous and measuring >3 mm in diameter, often involve, or are associated with, the main superficial trunks and can be easily assessed with ultrasound. Varicose veins most commonly occur due to incompetence of the GSV or SSV, or a combination of both systems.

It is important to identify the supply to the varicose areas and the level of incompetence in the GSV or SSV. This can be highly variable but frequently involves reflux from the saphenofemoral or saphenopopliteal junctions. In some situations varicose veins may be independent of the GSV or SSV systems, such as the lateral thigh. Much debate has surrounded the development of varicose veins, but it appears that incompetence in the main trunks develops distally, in the lower leg, and progresses in a proximal direction over time. This is contrary to traditional teaching, which proposed that incompetence developed at the SFJ, leading to progressive valve failure in a descending direction. The model of progressively ascending valve failure would also explain why it is possible to observe segmental GSV reflux in the lower thigh but competence of the vein in the upper thigh and at the SFJ (Abu-Own et al. 1994). Some patients with superficial varicose veins may also have coexisting deep venous insufficiency.

Skin changes and venous ulcers

A serious complication of superficial or deep venous insufficiency is the development of chronic venous hypertension in the lower limb, resulting in venous ulceration (Fig. 13.13). Risk factors associated with ulceration include post-thrombotic syndrome, obesity, immobility, and arthritic conditions, which cause reduced movement of the ankle joint, leading to failure of the calf muscle pump. It is important to note that some ulcers that may appear to be venous in origin are caused by other conditions, such as vasculitis, rheumatoid arthritis, or skin disorders. The underlying cause of ulceration is still unclear but is thought to involve changes in the microcirculation of the skin and subcutaneous tissues in response to local venous hypertension. The venous hypertension causes an increase in venular and capillary pressure, leading to local edema and reduced reabsorption of proteins and fluid from the interstitial tissue spaces. This is combined with damage to the capillary walls, which may cause localized tissue hypoxia. Leakage of red blood cells across the damaged capillary wall and into the interstitial tissue spaces produces the brown pigmentation associated with many ulcers. This is due to hemosiderin deposition caused by the breakdown of the red blood cells. Venous ulcers are usually reasonably shallow and vary in size, and in some cases they may be circumferential around the calf. They frequently become infected with different types of bacteria and can be extremely painful.

Figure 13.13 A picture of a venous ulcer involving the lower aspect of the medial calf and ankle. Varicose veins are also seen in the great saphenous vein distribution of the mid-calf.

Skin changes around the ankle or lower calf are the first physical signs of venous hypertension. This is typically seen as areas of venous eczema and pigmentation, frequently associated with local skin irritation or itching. There is often development of lipodermatosclerosis, typified as hardening of the subcutaneous tissues in the lower calf and ankle, giving a hard, ‘woody’ feel to the area. The development of an ulcer is sometimes initiated by a minor injury or abrasion that fails to heal. It is important to remember that some venous ulcers are also associated with arterial disease, and patients with mixed venous and arterial ulceration pose a challenging diagnostic problem for the vascular laboratory. It is therefore routine practice to measure the ankle–brachial pressure index (ABPI) in all patients with venous ulceration to exclude a significant arterial component. However, in some situations it may be impossible to measure the ABPI due to pain, and a subjective assessment of the pedal artery waveforms will have to suffice. A layer of cling film or Saran wrap is ideal for wrapping around areas of ulceration to protect the ulcer and to keep the pressure cuff clean.

Historically, it was thought that venous ulceration was primarily due to deep venous insufficiency following valve failure, postthrombotic syndrome, or failure of the calf muscle pump, resulting in deep venous hypertension. However, later studies (Scriven et al. 1997; Magnusson et al. 2001) demonstrated that a significant number of patients with ulceration have superficial reflux alone, with the deep veins being competent. Therefore, ligation of the relevant superficial vein junction, with or without stripping of the superficial vein, results in the healing of the majority of ulcers due to the reduction in venous hypertension. The role of perforator ligation remains controversial, but there is evidence that chronic venous insufficiency is associated with an increase in the number and diameter of medial calf perforators (Stuart et al. 2000). Presurgical marking of incompetent perforators may be performed with the aid of the duplex scanner.

Varicose ulcers caused by superficial incompetence alongside significant deep venous insufficiency are not usually treated by the ligation or stripping of superficial varicose veins, as the underlying deep venous hypertension will not be corrected. Instead, the use of compression bandaging, which reduces edema and venous hypertension, has proved to be an effective method of healing ulcers. Different grades of compression bandaging can be used depending upon the clinical situation (Lambourne et al. 1996). However, an ABPI of ≥0.8 is required for the application of four-layer compression dressings, in order to avoid arterial compromise in the tissues under the bandaging. This can be a serious complication and can lead to limb loss in extreme cases.

Treatment of superficial venous disorders

A range of treatment options is available depending on the severity of the condition (Browse et al. 1999). Conservative treatment is with compression hosiery. Thread veins can be treated by microinjection sclerotherapy, followed by local compression to occlude the vein. They can also be treated by local laser therapy. Larger varicose veins can be treated by a variety of methods, including foam sclerotherapy, open surgery, or endovenous ablation. Some patients undergo combined procedures to achieve optimum results. In the case of open surgery for primary GSV incompetence, the SFJ and tributaries are ligated at the groin, and the main trunk stripped with a vein stripper to knee level or below. Surgery of the SSV normally involves ligation of the saphenopopliteal junction. Some surgeons strip the vein, but others leave it intact to avoid injury to the sural nerve, which is closely associated with the vein. Some surgeons also ligate large perforators, and these can be marked preoperatively with the aid of duplex scanning. Any remaining veins are then removed or avulsed using small microincisions. It is worth observing some varicose vein surgery as it gives a better appreciation of the anatomy seen during duplex examinations.