Presence and degree of residual venous obstruction on serial duplex imaging is associated with increased risk of recurrence and progression of infrainguinal lower extremity deep venous thrombosis

Objective: The role of follow-up venous duplex ultrasound (DUS) after acute lower extremity deep vein thrombosis (DVT) remains unclear, yet it is commonly performed. We aimed to clarify the role of follow-up DUS. Our primary objective was to determine the association between the presence of residual venous obstruction (RVO) on DUS and DVT recurrence or propagation (rDVT). Secondary objectives included finding risk factors associated with RVO and rDVT. Methods: We conducted a retrospective study of patients diagnosed with DVT on DUS from January 1, 2011, to December 31, 2013, that received a follow-up DUS. Patient demographics, risk factors, medications, and DUS findings were recorded. Ten segments from the common femoral to distal calf veins were checked for the presence of RVO, DVT propagation, and recurrence. RVO was defined as any nonacute venous obstruction with more than 40% of luminal diameter remaining during compression or the presence of chronic post-thrombotic occlusive disease. rDVT was measured as either a new acute DVT in the previously involved segment, or involvement of a new segment in the same extremity. Results: A total of 185 lower extremities representing 156 patients met the inclusion criteria. RVO was noted in 61.1% of limbs. The 3-year rDVT rate was 10.3%. Patients with recurrent venous thromboembolism or thrombophilia had a higher risk of developing RVO (odds ratio [OR], 2.89, P <.01; OR, 4.39, P =.04, respectively). Extremities with larger clot burden had an increased risk of RVO on follow-up DUS (OR, 1.25 per segment; P <.01). The presence and degree of RVO on follow-up DUS had an increased risk of rDVT on subsequent DUS (OR, 3.90, P =.04; OR, 1.21 per segment, P = .04, respectively). Limbs with complete resolution of DVT by DUS had a significantly decreased risk of rDVT (OR, 0.26; P = .04). Conclusions: Extremities with larger initial clot burden exhibited an increased risk of subsequent RVO. The presence of RVO and, interestingly, the number of involved segments on follow-up DUS increased the risk of rDVT. Our results suggest that the presence of residual disease and increased RVO burden on follow-up DUS after an acute DVT may identify those patients who are at an increased risk for rDVT and may help guide the duration of anticoagulation therapy.