Do isolated calf deep vein thrombosis need anticoagulant treatment?

Isolated calf deep vein thrombosis (ICDVT), defined as thrombosis confined to the infra-popliteal veins of the lower limbs, is a frequent finding in symptomatic out- and in-patients when the ultrasound examination is extended to the whole deep leg veins. Studies based on a complete investigation of deep veins in the whole leg, reported a prevalence of ICDVT of 7–11% in cases with suspected PE, 4–15% in cases with suspected DVT, and 23–59% in patients with diagnosis of DVT (1). Notwithstanding these high figures, many and clinically relevant aspects of ICDVT are still controversial; in fact, that of ICDVT is currently one of the most debated issues in the field of venous thromboembolism (VTE). First of all, whether an extended ultrasound examination of calf deep veins is necessary in all suspected subjects is still matter of discussion and the American College of Chest Physician guidelines on VTE in the last edition (2) propose a rationale for not routinely examining the distal veins, based on the facts that: (I) other assessment (e.g., low clinical probability and/or negative D-dimer) may help guiding those in whom distal examination is not necessary; (II) a repeat ultrasound of the proximal veins can be done after a week to identify those patients with a risky proximal DVT; and finally, (III) false-positive findings for DVT may occur with a subsequent unnecessary and risky anticoagulant treatment to a number of subjects. Moreover, even in the case that the calf veins are imaged and ICDVTs are diagnosed, the above mentioned guidelines suggest two different management options as equally suitable in clinical practice: (I) to treat patients with anticoagulant therapy; or (II) to not treat patients with anticoagulant therapy unless extension of their DVT is detected on a follow-up ultrasound examination (e.g., after 1 or 2 weeks). However, important differences on this issue are present among currently available international guidelines on VTE; these differences reflect the broad variability in clinical practice between the strategies on how to manage patients with suspected leg DVT and even on how to treat ICDVT after diagnosis. The treatment for ICDVT is even not mentioned at all by the National Clinical Guideline Centre (last published in June 2012) since the guideline “…focused on proximal DVT rather than isolated calf vein DVT as the latter is less likely to cause post-thrombotic syndrome than proximal DVT and also less likely to embolize to the lungs.” (3). In contrast, the International Consensus Statement on prevention and treatment of VTE affirms