Investigating DVT - The BMJ

Investigating DVT

Visual summary

An approach to symptoms suggestive of lower limb deep vein thrombosis (DVT)

Clinical suspicion of DVT

Venous clot

Common symptoms: Swelling

Redness

Patients may also be asymptomatic, having had investigation for other conditions such as pulmonary embolism or malignancy

Pain

Typically throbbing in nature, and comes on while walking or bearing weight

Critical features or limb threatened

Swelling and inflammation below site of blockage

Modified Wells score (2003) Active cancer treatment (ongoing, within 6 months, or palliative)

+1

Localised tenderness along distribution of deep venous system

+1

Pitting oedema (greater in symptomatic leg)

+1

Paralysis, paresis, recent immobilisation of the lower limbs Entire leg swelling

Collateral superficial veins (non-varicose)

Total score: –2 –1 0

+1

Recently bedridden for more than 3 days, or major surgery within 4 weeks

+1

+1

Calf swelling >3cm compared with asymptomatic leg

+1

Previous documented DVT

+1

1

2

3

4

DVT unlikely

The D-dimer blood test has high sensitivity but is not very specific. D-dimer can be raised in other conditions, including: Malignancy

Infection

Pregnancy

Post surgery

Inflammation/trauma

Negative

7

8

9

Either proximal or whole leg ultrasound is recommended in high risk cases

Lower limb ultrasound Positive

Proximal, above knee ultrasound is recommended in low risk cases

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Negative

Positive

Discuss with specialist Consider interim ultrasound or alternate imaging

If diagnostic testing will take longer than 4 hours, begin interim anticoagulation treatment

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Lower limb ultrasound

Positive

Negative

DVT excluded

6

–2

+1

DVT likely

If D-dimer not available or inappropriate

High/moderate sensitive D-dimer test

5

Alternative diagnosis as likely, or more likely than DVT

Treat as DVT

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