Role of Ultrasound Elastography in Distinction Between Acute and Chronic Deep Vein Thrombosis: a Prospective Observational Cohort Study

Compression ultrasonography (CUS), supplemented with color-Doppler, is the gold-standard for the diagnosis of deep vein thrombosis. However, it cannot provide adequate information on the timing of the onset of thrombosis, thus not allowing a distinction between acute and chronic venous thrombosis. A few non-standardized and poorly reproducible criteria are used in clinical practice, such as thrombus echogenicity, degree of occlusion and signs of recanalization. The importance of the distinction between acute and chronic venous thrombosis has therapeutic and prognostic implications, especially in patients with occasional and asymptomatic finding of venous thrombosis or in patients with suspected thrombotic recurrence in whom signs and symptoms may be either due to a post-thrombotic syndrome or to a new thrombotic episode.

Shear-Wave elastography, a technique used to assess tissue elasticity and widely used in hepatology, could play a crucial role in distinguishing between acute and chronic deep vein thrombosis. Literature data on the use of this technique in the evaluation of deep venous thrombosis are derived only from observational studies, both retrospective and prospective, mainly based on comparisons between different groups of patients with acute (within 72h from diagnosis) or subacute thrombosis at a 3-months follow-up, with the consequent risk of confounding in the estimating the association of elasticity values to the dating of thrombotic remnant. The few data in the literature on thrombus evolution, assessed by single-patient serialized evaluation, refer to extremely limited case series with short follow-up. In addition, none of these studies consider neoplastic patients, on whom there are no data regarding the usefulness and reproducibility of the method. In accordance with current clinical practice, patients referred to our service of Internal medicine and Thromboembolic Pathology perform ultrasound follow-up so that the evolution of thrombotic residual can be assessed on each patient with large case series and follow-up of longer duration. The primary objective of the present study is to evaluate the efficacy and diagnostic and prognostic accuracy of Shear-Wave elastography in distinguishing between acute and chronic deep vein thrombosis.

Secondary objectives:

• Evaluation of the maximum thickness of the thrombotic residue in compression, as well as the longitudinal extent by B-mode ultrasound method, expressed in mm, at the various time-points of the study
• Evaluation of the degree of venous obstruction, assessed by color-Doppler ultrasound method at the various time-points of the study
• Qualitative evaluation of the echogenicity of the thrombotic remnant, by B-mode ultrasound method in comparison with the echogenicity of the surrounding muscle and vascular structures, at the various time-points of the study.
• Identification of a specific signature for recanalization of deep vein thrombosis of the lower and upper limbs