We suggest the following as risk factors for extension of distal DVT that would favor anticoagulation over surveillance: (1) D-dimer is positive (particularly when markedly so without an alternative reason); (2) thrombosis is extensive (eg, >5 cm in length, involves multiple veins, >7 mm in maximum diameter); (3) thrombosis is close to the proximal veins; (4) there is no reversible provoking factor for DVT; (5) active cancer; (6) history of VTE; and (7) inpatient status.1,75-77,80-84 We consider thrombosis that is con ned to the muscular veins of the calf (ie,, soleus, gastrocnemius) to have a lower risk of extension than thrombosis that involves the axial (ie, true deep; peroneal, tibial) veins.76,81,85 Severe symptoms favor anticoagulation, a high risk for bleeding (Table 11) favors surveillance, and the decision to use anticoagulation or surveillance is expected to be sensitive to patient preferences. We anticipate that isolated distal DVT that are detected using a selective approach to whole-leg US will often satisfy criteria for initial anticoagulation, whereas distal DVT detected by routine whole-leg US often will not. The updated literature search did not identify any new randomized trials that assessed management of patients with isolated distal DVT. Two new systematic and a narrative review83 addressed treatment of isolated distal DVT. In addition to summarizing available data, consistent with AT9, they emphasize the limitations of available evidence. In the absence of substantive new evidence, the panel endorsed the AT9 recommendations without revision. The evidence supporting these recommendations remains low quality because it is not based on direct comparisons of the two management strategies, and ability to predict extension of distal DVT is limited. 13. 