flow is antegrade (going to the heart), and from superficial to deep veins via perforator veins. however, there are two exceptions: firstly, the gsv collaterals, (the veins that run parallel), drain the abdominal wall and have a flow from top to bottom so that when an examiner tests the saphenofemoral junction, a false positive diagnosis might be made; secondly, in the flow from the sole of the foot venous network around 10% drains to the dorsal venous arch of the foot, going therefore against the norm, from deep to superficial veins. attention will be focused on the direction of the blood flow in both of the venous systems, and in the perforator veins, as well as being focused on shunt detection. a shunting of blood from the thigh veins back into the lower leg veins will give a reflux situation. the veins most often found to be incompetent are the saphenous veins and the perforators communicating with the deep veins of the thigh. technical difficulties venous ultrasonography of the lower limbs is the most demanding of the medical complementary examinations. it is dependent on the examiner's expertise and training, and the interpretation of the results is subjective and reliant on an understanding of venous hemodynamics. (a mapping does help the reproducibility and the inter-observer agreement of this examination). the examination is made even more difficult because there can be dilated veins without insufficiency, (by hyper-debit), and non dilated but incompetent veins. moreover, veins can be discretely incompetent in summer but then be normal in winter. also, by definition of insufficiency, (insufficient blood flow) blood may be seen to flow freely in both directions, antegrade and retrograde between two valves. another problem when dealing with the superficial venous system, is that venous anatomy is not constant; the position of veins can vary in different patients; also in the same patient the right lower limb is not identical to the left lower limb. as a further complication to the examination, where venous insufficiency is evidenced, the examination needs to be done with the probe in the transversal position but the mapping must be done showing the veins in their longitudinal aspect. this demands a rapid extrapolation by the physician from the transversal images seen to the longitudinal drawing needed. the dynamic maneuvers also need to be well executed. the need of a specialized training is mandatory which is a huge problem for many countries today. particular details great saphenous vein the "eye sign" the gsv a superficial vein, is the longest vein in the body. it has its origin in the dorsal venous arch of the foot, a superficial vein which connects the small saphenous vein with the gsv. it travels up the leg and medial side of the thigh to reach the groin, where it drains into the common femoral vein. along the length of the gsv, it receives numerous tributaries, (from the subcutaneous layer) and drains into the deep veins via the perforator veins. when seen in a scan, the gsv and the giacomini vein, together with the accessory saphenous vein (asv), form an image resembling an eye which is referred to as the "eye sign" or "eye image". . all veins which are between the skin and the superficial fascia are tributaries and all veins which cross the deep fascia to join the deep venous system are perforator veins. three anatomic compartments can be described, as networks: n1 contains the deep veins, also known as the deep compartment. n2 is the superficial compartment or the saphenous compartment. n3 is the epifascial compartment. some authors describe one more compartment n4, containing collaterals which form a bypass between two distinct points of the same vein. this compartmentalization is useful in an ultrasonographic examination because it makes systematization, mapping execution, and any surgery strategic, easier. carrying out vein mapping being protected between two fasciae, the superficial veins belonging to compartment n3 very rarely become sinuous. so that when a sinuous vein is detected, the sonographer will suspect that it is a tributary. the sapheno-femoral junction is tested by the valsalva maneuver with the use of color doppler being helpful at this stage. the wall thickness of the vein is significantly increased in venous reflux, being approximately 0.58 mm in venous reflux, compared to up to 0.45 mm normally. accessory saphenous vein asv at sapheno-femoral junction, the "mickey mouse sign" the accessory saphenous vein (asv), either anterior or posterior, is an important gsv collateral frequently responsible for varicose veins located on the anterior and lateral aspect of the thigh. the anterior asv is more anterior than the asv and is outside the femoral vessels plan. the two veins terminate in a common trunk near the groin, the sapheno-femoral junction. here, the asv can be located aligned with the femoral vessels at the "alignment sign". also, at the groin it can be seen at the outside of the great saphenous vein, and together with the common femoral vein (cfv) these three create an image, the so-called "mickey mouse sign". some authors, inspired by this sign (presented for the first time at chiva's 2002 meeting in berlin), described a "mickey mouse view" at the groin, an image formed by the common femoral vein, the gsv and the superficial femoral artery. when the asv is incompetent, its flow becomes retrograde and tries to drain in the superior fibular perforator, at the side of the knee, or sometimes it runs down towards the ankle to drain in the inferior fibular perforator. small saphenous vein the small saphenous vein (ssv), runs along the posterior aspect of the leg as far as the popliteal region, in the upper calf. here it enters the popliteal space which is located between the two heads of the gastrocnemius muscle where it usually drains above the knee joint in the popliteal vein or a little less often in the gsv or other deep muscular veins of the thigh. the use of ultrasonography has allowed a number of variations to be shown at this level; when no contact is made with the popliteal vein it might be seen to drain in the gsv, at a variable level; or, it may merge with the giacomini vein and drain in the gsv at the superior 1/3 of the thigh. it can also but rarely, drain in the vein of the semimembranosus (thigh muscle) (shown below). usually though, it connects with a perforator vein at its middle 1/3. to check for insufficiency, the paraná maneuver is very useful. insufficiency from the ssv at sapheno-popliteal junctioninsufficiency from the ssv flooded by the vein of the semimembranosus musclessv variant draining in the vein of the semimembranosus muscle giacomini vein the giacomini vein mostly acts as a bypass between the gsv and ssv territories. usually its flow is in the normal antegrade direction, from bottom to top. however it can become retrograde without pathology. for example, after a gsv stripping, laser ablation or after its ligation at the sapheno-femoral junction, the giacomini vein will drain into the ssv, with a retrograde flow. when there is a gsv thrombosis or other cause of insufficiency, the giacomini vein can divert the blood flow to the ssv and from there to the popliteal vein. where surgery, other than stripping or laser ablation is intended, the examiner will make reference to the blood flow direction in this vein, as it will be of importance. perforator veins insufficient perforator perforator veins play a very special role in the venous system, carrying blood from superficial to deep veins. during the muscular systole their valves close and stop any blood flow coming from the deep to the superficial veins. when their valves become insufficient, they are responsible for a rapid deterioration in existing varicose disease and for the development of venous ulcers. detection of insufficient perforators is important because they need to be ligatured. however, the detection of competent ones is as important because they may be used strategically in new techniques of conservative surgery, for example a minimally invasive chiva. the ultrasonography report will include insufficient and continent perforators, which will also be shown on venous mapping. to test these veins properly, the examiner will need to use some techniques like the paraná maneuver, toe and foot flexion, and hyper-extension on tip toes. examination report svs normal mapping after performing this examination, the physician writes a report in which some points are crucial: the condition of the deep vein system (dvs), its permeability and compressibility, and whether it is continent or insufficient; the permeability and compressibility of the superficial vein system (svs), the presence or absence of superficial insufficiency, and in which veins or vein segments; which perforator veins are continent or insufficient; the presence or absence of shunts; mapping the insufficient veins, flux direction, shunts, and perforators. this enables surgeons to plan interventions, in a stage known as virtual dissection. drawn on paper, after the examination, it will be drawn over the patient's skin before surgery. history the doppler effect was first described by christian doppler in 1843. nearly forty years later in 1880, the piezoelectric effect was discovered and confirmed by pierre and jacques curie. both of these findings were used in the development of ultrasonography. the first ultrasound was applied to the human body for medical purposes by dr. george ludwig, university of pennsylvania, in the late 1940s. the use of ultrasonography in medicine soon followed in different locations around the world. in the mid-1950s more research was undertaken by professor ian donald et al., in glasgow, which advanced the practical technology and applications of ultrasound. in 1963, in france, léandre pourcelot started on his thesis, which was presented in 1964, and used pulsed doppler for blood flow calculation as its subject. this was followed up by peronneau in 1969. dr. gene strandness and the bio-engineering group at the university of washington who conducted research on doppler ultrasound as a diagnostic tool for vascular disease, published their first work in 1967. the first report published about the venous system appeared around 1967–1968. a few years later in 1977, claude franceschi published the very first book about vascular ultrasonography, l’investigation vasculaire par ultrasonographie doppler. from the 1960s commercially available systems were introduced. soon, other advances in electronics and piezoelectric materials enabled further improvements which meant that ultrasound was quickly adopted for use in medicine due to its rapid, accurate diagnostic capabilities which offered the possibility of prompt treatment. alongside the improving imaging technology, acoustic doppler velocimetry and medical ultrasonography color doppler were developed, which have had a significant impact on many specialties, including radiology, obstetrics, gynecology, angiology and cardiology, and have provided even greater scope for ultrasound investigations. since 1970, real-time scanners and pulsed doppler, have enabled the use of ultrasound to study the function of the venous system. the first demonstration of color doppler was achieved by geoff stevenson. further progress in the 1970s was made with the arrival of the microchip, and the ensuing exponential increase in processing power has meant the development of fast and powerful systems. these systems involving digital beamforming and greater signal enhancement, have introduced new methods of interpreting and displaying data rapid technical advancements in transmission tomography made possible the very good specificity and sensitivity capability of this technique, enabling the possibility of properly seeing the superficial tissues. footnotes interface is the plane between two tissues with a different density, for instance skin-fat-aponevrosis-muscle echogenic is the tissue which reflects the ultrasound beam and can be visualized on the screen in venous circulation, shunt is the situation where blood circulates from one vein (leak point) to another and from this one to the former (re-entry point) creating a pathway in a vicious circle between two veins one with a physiologic flow and the other with a retrograde flow mapping is a schematic depiction of the venous anatomic-functional configuration in an individual virtual dissection is a schema based on venous mapping where the surgeon projects what he will do to treat his patient.