Should we be looking for and treating isolated calf vein thrombosis?

Management of isolated calf deep vein thrombosis is an area of significant international debate and variable clinical practice. Both therapeutic anticoagulation and conservative management carry risk. As clinical care of suspected and confirmed venous thromboembolic disease increasingly becomes the remit of emergency medicine, complex decisions are left to practising clinicians at the front door. We aim to provide a contemporary overview of recent evidence on this topic and associated challenges facing clinicians. Given the lack of high-level evidence, we present this work as a narrative review, based on structured literature review and expert opinion. A decision to manage calf thrombosis is principally dependent on the risk of complications without treatment balanced against the risks of therapeutic anticoagulation. Estimates of the former risks taken from systematic review, meta-analysis, observational cohort and recent pilot trial evidence include proximal propagation 7%-10%, pulmonary embolism 2%-3% and death <1%. Fatal bleeding with therapeutic anticoagulation stands at <0.5%, and major bleeding at approximately 2%. Estimates of haemorrhagic risk are based on robust data from large prospective management studies of venous thromboembolic disease; the risks of untreated calf deep vein thrombosis are based on small cohorts and therefore less exact. Pending further trial evidence, these risks should be discussed with patients openly, in the context of personal preference and shared decision-making. Anticoagulation may maximally benefit those patients with extensive and/or symptomatic disease or those with higher risk for complication (unprovoked, cancer-associated or pregnancy).