Wai Khoon Ho
Deep vein thrombosis
Risks and diagnosis
Venous thromboembolism (VTE), comprising deep vein thrombosis and pulmonary embolism (PE), is the third commonest vascular disorder in Caucasian populations.1 In Australia, DVT alone (without concomitant PE) affects 52 persons per 100 000 annually.2 Timely management of DVT is important as it is a common cause of morbidity. Thromboses of the deep veins in the upper limbs and ‘unusual sites’, such as mesenteric veins, constitute less than 10% of DVT cases.2 As they are uncommon, this article focuses only on the risks and diagnosis of lower limb DVT. Deep vein thrombosis usually starts in the calf area.3 most thrombi confined to the deep veins below the popliteal trifurcation (distal DVt, Figure 1) probably resolve spontaneously without causing any symptoms. Distal DVt can extend to the popliteal and femoral veins and other proximal veins. (note that in some imaging reports, the term ‘superficial femoral vein’ is applied to that part of the femoral vein between the popliteal vein and the confluence with the deep femoral vein.4 the superficial femoral vein is therefore a part of the proximal deep venous system.) most patients present with symptoms when there is proximal vein involvement. About 50% of patients with untreated symptomatic proximal DVt develop symptomatic PE within 3 months. Despite adequate treatment, DVt can recur. About 10% of patients with symptomatic DVt develop severe post-thrombotic syndrome within 5 years.3
Venous thromboembolism, comprising deep vein thrombosis (DVT) and pulmonary embolism, is common in Australia and is associated with high morbidity.
This article provides a summary of the risk factors for DVT of the lower limb and discusses the diagnosis of the condition using a diagnostic algorithm incorporating clinical assessment, D-dimer testing and imaging studies. It also briefly reviews the clinical significance of isolated distal lower limb DVT and superficial vein thrombosis.
Many conditions in the lower limb mimic DVT. Diagnosing DVT on clinical grounds without objective testing is unreliable. Patients incorrectly diagnosed as having DVT may be subjected to unnecessary anticoagulation and its associated risks of bleeding. In contrast, there is a risk of thrombus extension and embolisation when DVT is missed or inappropriately treated.
Keywords: venous thrombosis; thrombophlebitis; risk
Risk factors for VTE
Venous thromboembolism may be provoked by transient and reversible clinical risk factors such as surgery or oestrogen exposure, or long term and permanent factors, such as hemiparesis from stroke (Table 1).5 in 25% of cases, no clinical cause can be ascertained (idiopathic VtE).6 About 40–60% of VtE patients in caucasian cohorts have thrombophilia – a haemostatic disorder resulting in a thrombotic tendency.7 this may be heritable (eg. factor V leiden, prothrombin gene mutation and deficiencies of protein c, protein s and antithrombin),7 or acquired (eg. antiphospholipid antibodies).8
468 Reprinted from AustRAliAn FAmily PhysiciAn Vol. 39, no. 7, July 2010
Inferior vena cava
Table 1. Clinical risk factors for venous thromboembolism5 Strong clinical risk factors (odds ratio >10) • ractureofthehiporlowerlimb F • iporkneereplacementsurgery H • ajorgeneralsurgery M • ajortrauma M • pinalcordinjury S Moderate clinical risk factors (odds ratio 2–9) • rthroscopickneesurgery A • ormonaltherapy(eg.oralcontraceptives,hormone H replacement therapy) • regnancy–postpartum P • aralyticstroke P • reviousvenousthromboembolism P Weak clinical risk factors (odds ratio 3days,airtravel>8 I hours) • regnancy–antepartum P • besity O • dvancingage A
Common iliac vein External iliac vein Common femoral vein Deep femoral vein
Great saphenous vein (superficial vein)...