ABC | Volume 112, Nº6, June 2019

Statement Vascular Ultrasound Statement from the Department of Cardiovascular Imaging of the Brazilian Society of Cardiology – 2019 Arq Bras Cardiol. 2019; 112(6):809-849 Figure 17 – Venous compression maneuver. (A) Artery and vein without compression. (B) Normal vein with total compression. (C) Dilated and incompressible vein, with recent thrombus. (D) Incompressible vein, with old thrombus (chronic). (E) Rethrombosis. 6.2.2. Vascular Ultrasound VUS is considered the current gold standard examination to diagnose acute DVT. 99 The PIOPED II study showed 95.5% agreement between CTA and ultrasound in diagnosing or ruling out DVT. In addition, we must remember that VUS is useful not only in diagnosing DVT in symptomatic or asymptomatic (with a high risk of DVT) patients but also in identifying other conditions that cause signs and symptoms indistinguishable from DVT. Knowledge about vascular anatomy and its variations is crucial since the frequency of variability in the number of veins is high, with the possibility of only one of them being involved, in addition to the different levels of confluences and paths. To diagnose thrombosis, we adopt several criteria, listed below. 1. Venous compression: the normal vein has thin, smooth, and regular walls, and is completely collapsible with transducer compression (Figure 17). Incompressibility is the main criterion for DVT diagnosis (Figure 16). A few conditions might hinder this compressibility, and sometimes special maneuvers are necessary. They are: • Presence of a strong muscle group in the path to be compressed; for instance, the adductor canal requires compression in the external side of the thigh. • Neurogenic bladder needs draining through urinary catheterization. • Proximity to bone structures; for example, compression is limited in infrapatellar veins due to the size of the transducer. 2. Vein caliber: usually the vein has twice the caliber of the adjacent artery. Acute venous thrombosis presents great distension of the vessel wall, with an increase in vein caliber and loss of this relationship. Over time, with the process of recanalization, the vein caliber decreases disorderly in some segments, losing the uniformity usually observed along the vessels. In themost chronic stage, a complete vein retractionmight occur, with calibers becoming smaller than those of arteries, at times, hindering their recognition during the examination. 3. Characteristics of the venous wall: parietal irregularities or diffuse parietal thickening, intraluminal trabeculations or synechia, structural valve abnormalities, loss of anatomical relationship with adjacent structures, even if tenuous, which can mean a previous DVT already recanalized. Intraluminal echoes indicate presence of thrombus and its echogenicity can characterize or not its age. 4. Color imaging: color flow imaging is an important tool for venous thrombosis. While color flow filling all lumen in longitudinal and transverse planes indicates normality, the lack of color or flaws in filling the vessel can point to partial or complete thrombosis, particularly in recent partial thrombi with low echogenicity. Flow around the vessel strongly suggests acute DVT. Flow permeating the thrombus indicates recanalization and chronicity of the process. Take precautions regarding the scale and gain of the equipment, and the proper performance of maneuvers that increase venous flow, generating a color signal. 5. Spectral analysis: the normal venous flow with spectral Doppler is spontaneous and phasic with respiration, increases with distal compression maneuvers, and ceases with Valsalva maneuvers (proximal veins) or proximal compression. 85 The spontaneity of the flow might not be observed in distal veins of patients in the supine position, and distal compression maneuvers and/or mobilization of the limb to displace the blood column become necessary. Loss of phasicity, with continuous flow pattern, is an indirect sign of occlusion or proximal compression. Damped response to distal 836