ultrasonography of chronic venous insufficiency of the legs ultrasonography of chronic venous insufficiency of the legs ultrasonography of suspected or previously confirmed chronic venous insufficiency of leg veins is a risk-free, non-invasive procedure. it gives information about the anatomy, physiology and pathology of mainly superficial veins. as with heart ultrasound (echocardiography) studies, venous ultrasonography requires an understanding of hemodynamics in order to give useful examination reports. in chronic venous insufficiency, sonographic examination is of most benefit; in confirming varicose disease, making an assessment of the hemodynamics, and charting the progression of the disease and its response to treatment. it has become the reference standard for examining the condition and hemodynamics of the lower limb veins. particular veins of the deep venous system (dvs), and the superficial venous system (svs) are looked at. the great saphenous vein (gsv), and the small saphenous vein (ssv) are superficial veins which drain into respectively, the common femoral vein and the popliteal vein. these veins are deep veins. perforator veins drain superficial veins into the deep veins. three anatomic compartments are described (as networks), (n1) containing the deep veins, (n2) containing the perforator veins, and (n3) containing the superficial veins, known as the saphenous compartment. this compartmentalisation makes it easier for the examiner to systematize and map. the gsv can be located in the saphenous compartment where together with the giacomini vein and the accessory saphenous vein (asv) an image resembling an eye, known as the 'eye sign' can be seen. the asv which is often responsible for varicose veins, can be located at the 'alignment sign', where it is seen to align with the femoral vessels. lower limbs venous ultrasonographyultrasonography equipment. sonographic scannerpurposedetails of anatomy, physiology and pathology of superficial veins. on ultrasound at the saphenofemoral junction in the groin, the common femoral vein (cfv) with the gsv and the common femoral artery (cfa) create an image called the mickey mouse sign. the cfv represents the head, and the cfa and gsv represent the ears. the examination report will include details of the deep and the superficial vein systems, and their mapping. the mapping is drawn on paper and then drawn on the patient before surgery. the use of ultrasonography in a medical application was first used in the late 1940s in the united states. this use was soon followed in other countries with further research and development being carried out. the first report on doppler ultrasound as a diagnostic tool for vascular disease was published in 1967–1968. rapid advances since then in electronics, has greatly improved ultrasound transmission tomography. medical uses it allows the examiner to evaluate the gross anatomy of the venous networks as well as the blood flow direction, which is crucial in determining vein pathology. it has become the reference standard used in the assessment of the condition and hemodynamics of the veins of the lower limbs. the normal physiological blood flow is antegrade, flowing from the periphery towards the heart, so that the evidence of an opposite, retrograde flow might indicate a pathology. the presence of a reflux is likewise of note; a reflux when not isolated in a vein (as simply retrograde), means that the blood flow is bi-directional where once the flow had been only antegrade. risks no contraindications are known for this examination. ultrasonography does not involve the use of ionizing radiation, and the procedure is harmless and can be safely used on anybody of any age. a world health organization report published in 1998 supports this. preparation no preparation is normally necessary for this examination, but if a complementary study of abdominal veins is also required, the patient will be asked to fast for 12 hours beforehand. the sensitivity and specificity measurements are around 90%. equipment high frequency probe used for superficial ultrasonography the ultrasound equipment must be of sufficiently high quality in order to give a correct image processing result, which can then provide invaluable information, mainly at the superficial level. it must be able to provide both color and doppler imaging; technologies that developed alongside the development of ultrasound. the use of doppler measurements which trace the echoes of the generated soundwaves received by the probe, enable the direction and the velocity of the blood flow, to be depicted. the overlay of color onto the doppler information lets these images be seen more clearly. the choice of a probe will depend on the depth needed to be studied. for example, the superficial venous system (svs) can be very well examined using a high frequency probe of 12 mhz. for patients who have thick adipose tissue a probe of 7.5 mhz will be required. deep veins require probes of around 6 mhz whilst the abdominal vessels are better studied with probes of between 4 and 6 mhz. in summary, three probes are needed together with a top level scanner. also, the proper use of the scanner calls for a high level of expertise, so that the examiner must be well qualified and experienced in order to give effective results. in contrast to arterial ultrasonography the wall of the vein is not relevant and importance is given to the hemodynamic conclusions that the examiner can obtain in order to provide a valuable report. (hemodynamics is the study of blood flow and of the laws that govern the circulation of blood in the blood vessels). it follows that the examiner knowledge of venous hemodynamics is crucial, which can be a real barrier to a radiologist untrained in this field, who might wish to carry out these examinations. specialized training in venous ultrasonography is not undertaken in some countries, which undermines best practice, mainly when varicose veins need to be examined. mechanism main article: medical ultrasonography performing venous ultrasonography ultrasonography is based on the principle that sound can pass through human body tissues and is reflected by the tissue interfaces in the same way that light can reflect back on itself, from a mirror. tissue in the body will offer varying degrees of resistance, known as acoustic impedance, to the path of the ultrasound beam. when there is a high impedance difference between two tissues, the interface between them will strongly reflect the sound. when the ultrasound beam meets air, or solid tissue such as bone, their impedance difference is so great that most of the acoustic energy is reflected making it impossible to see any underlying structures. the examiner will see just a shadow, instead of the image expected. air will impede sound waves which is why a gel is used. the gel prevents air bubbles from forming between the probe, and the patient's skin and so helps the conduction of the sound waves from the transducer into the body. the watery medium also helps to conduct the sound waves. liquids, including blood have a low impedance, which means that little energy will be reflected and no visualization possible. one of the important exceptions is that when the blood flow is very slow it can in fact be seen, in what is termed "spontaneous contrast". this technology is widely used in confirming venous pathology diagnoses. the imaging capability needed, was made possible with the developments of doppler and color doppler. doppler measurements using doppler effect can show the direction of the blood flow and its relative velocity and color doppler is the provision of color to help interpret the image, showing for example, the blood flow towards the probe in one color and that flowing away another. whilst the equipment itself is costly, the procedure is not. apart from the scanner, different probes are required according to the depth to be studied. a gel is used with the probe to make a good acoustic impedance contact. the training and expertise of the examiner is important because of the many technical complications that can present. venous anatomy for example, is not constant, for example a patient's vein layout of the right limb is not identical to that of the left limb. the probe is an ultrasonic sensor, generally known as a transducer, which functions to send and receive acoustic energy. the emission is generated on piezoelectric crystals by the piezoelectric effect. the reflected ultrasound is received by the probe, transformed into an electric impulse as voltage and sent to the engine for signal processing and conversion to an image on the screen. the depth reached by the ultrasound beam is dependent on the frequency of the probe used. the higher the frequency the lesser the depth reached. procedure the patient will need to be in an upright position to enable a proper study of blood flow direction chronic venous insufficiency is where the veins cannot pump enough blood back to the heart. it results when the vein dilates secondary to a vein wall disease or when normal functioning of the valves, which serve to keep blood flowing to the heart and to prevent reflux, become damaged and/or incompetent (the dilation of a vein will prevent valves to close properly). this incompetence will result in an reversed blood flow through the affected vein or veins. it can result in varicose veins, and in severe cases venous ulcer. the reversed blood pools in the low third of legs and feet. unlike the arterial ultrasound study, when the sonographer studies venous insufficiency, the vein wall itself has no relevance and attention will be focused on the direction of blood flow. the objective of the examination is to see how the veins drain. in this way, venous ultrasonography has at times become a hemodynamic examination which is reserved for experienced sonographers who have completed hemodynamic studies and training and have acquired a deep knowledge of this subject. also, unlike ultrasonography of deep venous thrombosis, the procedure focuses mainly on superficial veins. also, unlike the arterial ultrasound examination, blood velocity in veins has no diagnostic meaning. veins are a draining system similar to a low pressure hydraulic system, with a laminar flow and a low velocity. this low velocity is responsible for the fact that it can only be detected spontaneously with the doppler effect on the proximal and larger femoral and iliac veins. here the flow is either modulated by the respiratory rhythm or is continuous in cases where the flow is high. the thinner veins do not have a spontaneous flow. however, in some circumstances the blood flow is so slow that it can be seen as some echogenic material moving within the vein, in "spontaneous contrast". this material can easily be mistaken for a thrombus, but can also easily be discounted by testing the vein's compressibility. vein valve and spontaneous contrast to evidence the blood flow direction there are some techniques that the examiner can use to accelerate blood flow and show valvular function: manual squeezing and releasing – the examiner can compress the vein below the probe which will push the blood in its normal antegrade direction. on releasing the pressure if the valves are incompetent the flow will appear as a retrograde flow or reflux, greater than 0.5 sec. paraná maneuver: checking perforators testing sapheno-popliteal junction with paraná maneuver paraná maneuver makes use of a proprioceptive reflex to test venous muscle pump induced flow. (proprioceptive refers to a response to a perceived stimulus especially with regard to movement and position of the body). a slight push to the waist, triggers a muscle contraction in the leg, in order to maintain posture. this maneuver is very useful for studying deep vein flow and detecting valvular incompetence, mainly at the popliteal vein level, (at the back of the knee) and to check perforator vein incompetence. it is very useful when legs are painful or very edematous (swollen with fluid). flexing the toes and feet and extending on tiptoes can all be very useful in detecting perforator vein incompetence. these movements unleash a muscle contraction which compresses deep veins. if a perforator valve is incompetent then a reflux from the deep to the superficial through the perforator vein will be registered. valsalva maneuver – when the patient performs this maneuver, he or she, increases intra-abdominal venous pressure. if the great saphenous valve at the sapheno-femoral junction is incompetent, a reflux will appear. valsalva maneuver is negativegsv insufficiency at s–f junction – valsalva positivegsv valsalva false positive – flow coming from an abdominal collateral at s–f junction normal blood