The patient will need to be in an upright position to enable a proper study of blood flow direction<unk><unk><unk>  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<unk>  ulcer. The reversed blood pools in the low third of<unk>  and feet. Unlike the arterial ultrasound study, when the sonographer studies<unk><unk> , 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,<unk> <unk>  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<unk>  of deep<unk>  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<unk>  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<unk>  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<unk>  pressure. If the great saphenous valve at the sapheno-femoral junction is incompetent, a reflux will appear. Normal blood 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<unk>  network around 10% drains to the dorsal<unk>  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<unk>  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<unk> <unk>  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<unk>  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<unk> , (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<unk> , (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<unk>  system, is that<unk>  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<unk><unk>  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.
Ultrasonography of chronic venous insufficiency of the legs
Ultrasonography of deep vein thrombosis
Peripheral vascular examination
Coronary CT calcium scan
Assessment of kidney function
Cardiac magnetic resonance imaging perfusion
Intracoronary optical coherence tomography
Pressure–volume loop analysis in cardiology