Table 1 A suggested guidance on appropriate venous US use according to type and risk factors in long-term follow-up of lower extremity DVT

Proximal DVT provoked from major transient risk factors

Or

Distal DVT ( provoked or unprovoked)

End of anticoagulation therapy ultrasound is less likely to be beneficial as treatment duration is time limited, i.e., 3 months and risk of future recurrence low [8,9, 23, 24, 33].

Proximal DVT provoked from minor transient risk factors

e.g.,air travel

Guidance on duration of anticoagulation beyond three months in this scenario differs among Various guidelines. Some suggest extended anticoagulation indefinitely [9]. Others suggest extesion only after evaluation of thrombotic and bleeding risk with periodic evluation and patient preference [8, 23]. A follow-up ultrasound at the end of planned anticoagulation may be considered.

Proximal unprovoked DVT

or

Proximal DVT provoked from major persistent risk factors e.g., active cancer.

Clinical “equipoise” is common regarding extension of anticoagulation beyond 3-6 months. after first unprovoked VTE. Most guidelines suggest indefinite anticoagulation among low bleeding risk patients [9, 24] or extended anticoagulation based on patient preference [8] and periodic bleeding re-assessment [23]. Among cancer assoicated thrombosis, patients with low bleeding risk would benefit from extended anticogulation as long as cancer ramains active [8, 9, 23, 24]. CDUS should be considerd in event of suspected DVT recurrence and may be considered towards end of planned anticoagulation. .

Distal provoked or unprovoked DVT, not treated with anticoagulation

Serial ultrasound once weekly, or earlier if worsening symptoms, for 2weeks

Further scanning beyond 2 weeks is generally not warranted [6, 10].

Residual venous occlusion or partial thrombus on end of therapy US follow-up

Further ultrasounds are unlikley to be beneficial as most guidelines support decision to continue or stop anticoagulation based on the risk of VTE recurrence from unprovoked or provoking risk factors, bleeding risk and patient preference. [6, 8, 24, 29].