Investigations

D-dimer: do if Wells score 1

Level decreased by heparin; normal levels with age

70-90% sensitivity in DVTs present 95% sensitivity and specificity for above knee; 70% sensitivity for below

knee; not good for iliacs

2-point USS much quicker; >95% sensitivity and specificity done in ED by experienced sonographer;

visualises 99% vessels

Venography: high sensitivity; painful; requires contrast; causes DVT in 1%

MRI: 80% sensitivity for below knee; MRI venography 100% sensitivity and specificity

Assessment

70% of hospitalised patients are asymptomatic; 1/3 patients asymptomatic overall; examination 75%

sensitivity, 45% specificity; diameter >2cm (60% sensitivity, 70% specificity), superficial thrombosis,

tenderness, Homans sign, fever

Wells Score: -2 for: alternative diagnosis more likely

+1 for: cancer in last 6/12 / immobilization / bed bound >3/7 or major surgery 3cm diameter / pitting oedema

collaterals

Low probability: 0 5% incidence of DVT

Moderate probability: 1-2 14% incidence of DVT

High probability: 3 50-80% incidence of DVT

Modified Wells Score: as above but +1 for PMH DVT

DVT unlikely: 1 3-9% incidence of DVT

DVT likely: 2 20-35% incidence of DVT

Bleeding, thrombosis, purpura fulminans, multi-organ failure, focal ischaemia, gangrene, oliguria, renal

cortical necrosis, ALI

External vessel compression: pregnancy, masses

In vessel wall: trauma, surgery, vasculitis

In blood: stasis (NWB, rigid immobilisation, bed rest >48 hours, travel, external fixation, paralysis, CCF,

major trauma, major surgert, obesity); hormynal (pregnancy, post-partum, OCP, HRT); hyperviscosity;

smoking, nephrotic syndrome; diabetes; cancer (esp adenocarcinoma or metastatic); haematological

problems (eg. Thrombophilia, plasminogen deficiency, platelet problems); hyperhomocystinaemia;

heparins; eldery

1:1000 overall; 1:100,000 in childhood; 1:100 in elderly; bilateral in 30%; in 6% patients with lower limb

injury; in 15% if immobilised >4/52; 8% annual recurrence rate if unprovoked, 2% if risk factors

Epidemiology

Risk Factors

Complications

DVT

Management

Elevation; ambulation; analgesia; stockings (wear for 2yrs; risk of VTE by 50%; post-thrombotic

syndrome by 50%)

Anticoagulation: risk of PE to 5%; recurrent thrombosis in 1st 3/12 by 80-90%; doesnt risk of

post-phlebitic syndrome

Mod/high probability: discharge after dose of heparin (40mg enoxaparin OD or 5000iu heparin BD)

USS within 12 hours

If DVT: continue LMWH until INR therapeutic (minimum 5/7, must overlap warfarin by minimum 4/7)

continue for 3/12 (life long if thrombophilia; not needed for below knee DVT unless continued risk

factors (eg. Thrombophilia, ongoing POP); propagation occurs in 20% below knee DVTs therefore do

repeat USS at 3-7/7; if not given heparin, give aspirin

Treat as inpatient if: severe oedema of whole lower limb; thrombus above groin

Thrombolysis: can incidence of post-phlebitic syndrome, lower incidence of venous ulceration,

complete lysis of thrombus in 30-40%; risk of embolism; indicated if massive iliofemoral thrombosis or

young patient with extensive venous thrombosis