By Dr. Marcus Judge

OSCE

During any examination in an OSCE it is important to understand the pathology and reasoning behind each of the signs and symptoms elicited, even if the patient being examined is ‘normal’. This article explains how to perform a deep vein thrombosis (DVT) examination and the key findings you should look for, showing you what each sign means and what conditions it may indicate.

A deep vein thrombosis is the formation of a thrombus (blood clot) within the deep venous system. It most commonly affects the veins of the calf, but it can also occur in the thigh, pelvis or, less often, the arm. The major concern with a DVT is that part of the clot can break off and travel through the venous system to the lungs. This causes a pulmonary embolism (PE), a potentially life-threatening complication. The DVT examination is a focused, mostly unilateral assessment of one leg compared with the other, aimed at detecting the clinical features of a clot and identifying any complications.

Contents

  1. Introduction
  2. General Inspection
  3. Closer Inspection of the Legs
  4. Palpation of the Legs
  5. Measuring Calf Circumference
  6. Assessment of Oedema
  7. Peripheral Pulses and Neurovascular Status
  8. Differential Diagnosis of a Swollen Leg
  9. Risk Factors and the Wells Score
  10. Completing the Examination
  11. Quiz

Introduction

Wash your hands thoroughly and don personal protective equipment if appropriate.

Introduce yourself to the patient and ensure to mention your grade e.g. 3rd year medical student/junior doctor/consultant.

Confirm the patient’s details taking 3 points of identification usually; full name, date of birth and NHS/hospital number.

Obtain consent for the examination, ensuring to explain what the examination will entail.

Ask the patient if they are currently experiencing any pain, particularly in the legs, as a DVT is frequently tender and you should be gentle when palpating.

Position the patient lying on the bed at 45 degrees, and expose both legs fully from the groin to the toes so that the two limbs can be directly compared. Maintaining the patient’s dignity, only expose what is necessary.

General Inspection

Begin by standing at the end of the bed and observing the patient as a whole. Note whether they appear comfortable or in distress, and look for signs that may point towards an underlying cause or complication. Patients with a DVT may be in pain from the affected leg, and those who have developed a pulmonary embolism may appear breathless (tachypnoeic), distressed, or be receiving supplemental oxygen.

Look around the bedside for objects and clues that give context to the patient’s condition. Relevant findings include compression stockings, evidence of recent surgery, mobility aids suggesting reduced mobility, intravenous lines, and monitoring equipment such as a pulse oximeter or oxygen mask. Many of the risk factors for DVT relate to venous stasis (immobility). Signs of recent immobilisation, such as a plaster cast, a walking frame or a recently operated limb, are therefore particularly relevant.

Compare the two legs side by side. A DVT is typically unilateral, so an obvious difference in size, colour or swelling between the two legs is an important early observation. Bilateral symmetrical swelling is much more likely to reflect a systemic cause such as heart failure, renal failure or hypoalbuminaemia (a low level of the protein albumin in the blood) than a DVT.

Closer Inspection of the Legs

Inspect both legs more closely, comparing the symptomatic leg against the asymptomatic side. Look specifically for the cardinal signs of a DVT:

  • Swelling: unilateral swelling of the calf or whole leg is the most consistent sign of a DVT. It is caused by the thrombus obstructing venous return and increasing venous pressure distal to the clot. This raised pressure forces fluid out of the capillaries into the tissues.
  • Erythema (redness): the skin overlying the affected segment may appear red and inflamed because of the local inflammatory response to the thrombus.
  • Dilated superficial veins: prominent, non-varicose superficial veins may develop as collateral channels (alternative routes around the blockage) when the deep veins are obstructed and blood is diverted into the superficial system.
  • Varicose veins: tortuous (twisted), dilated (widened) superficial veins are a marker of venous insufficiency (veins that do not return blood to the heart efficiently). They are not caused by an acute clot, but they signal abnormal venous function and are a recognised risk factor for a DVT, so note them when present.
  • Skin changes: longstanding venous disease can cause hyperpigmentation (brown discolouration from haemosiderin, an iron pigment left by broken-down blood), lipodermatosclerosis (hardening and tightening of the skin) and venous ulceration, typically around the medial malleolus (the bony bump on the inner side of the ankle).

In severe, extensive proximal thrombosis, the leg can become markedly swollen and discoloured. A pale, swollen leg is termed phlegmasia alba dolens. A tense, dusky, cyanotic (blue) leg is termed phlegmasia cerulea dolens. It represents near-complete venous outflow obstruction and is a vascular emergency that threatens the limb.

Deep Vein Thrombosis Swollen Right Leg SimpleMed

Image - A deep vein thrombosis of the right leg, showing unilateral swelling, redness and a visible increase in size compared with the left leg

Creative commons source by James Heilman, MD [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Also inspect for venous ulcers, which are a feature of chronic venous insufficiency and may coexist with, or follow, a previous DVT as part of post-thrombotic syndrome (long-term pain, swelling and skin change after a DVT). Venous ulcers are usually shallow, have an irregular border and characteristically occur in the gaiter area around the medial malleolus.

Venous Leg Ulcer SimpleMed

Image - A venous leg ulcer. Venous ulcers reflect chronic venous insufficiency and may follow a previous DVT as part of the post-thrombotic syndrome

Creative commons source by Jonathan Moore [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]

Palpation of the Legs

Before palpating, again confirm the patient is not in too much pain and warn them that you will be touching the leg, as a DVT is often tender.

Assess and compare the temperature of both legs using the backs of your fingers, working up the limb and feeling at several points so the two sides are compared at matching levels. An area that feels warmer than the contralateral leg supports the diagnosis, as the local inflammation around a thrombus increases blood flow and warmth to the overlying skin. Be aware that warmth is not specific to a DVT and is also seen in cellulitis (a spreading bacterial skin infection), which is an important differential for a hot, red, swollen leg.

Palpate gently along the line of the deep veins for tenderness. Tenderness along the deep venous system is one of the clinical features used to estimate the probability of a DVT. It is found particularly in the calf, popliteal fossa (the hollow behind the knee) and adductor canal (a channel in the middle of the inner thigh), and reflects the inflammatory reaction provoked by the clot within the vein.

While in the popliteal fossa, feel for any discrete swelling behind the knee. A fluctuant lump (soft and fluid-filled, so it moves under your fingers) here may be a Baker’s cyst, which can mimic a DVT. If it ruptures, it produces sudden calf pain and swelling that is clinically very difficult to distinguish from a clot. This is a recognised reason for an inconclusive examination that warrants ultrasound.

While palpating, also feel along any prominent superficial veins. A vein that feels firm, hard or cord-like and is tender, with overlying redness and warmth, suggests superficial thrombophlebitis: clot within a superficial vein accompanied by inflammation. This is a distinct entity from a DVT, but the two can coexist. Superficial thrombophlebitis of the long saphenous vein can also extend into the deep system, so it should always be noted and the deep veins assessed carefully.

You may have heard of Homans’ sign, in which forced dorsiflexion of the foot (pulling the foot up towards the shin) reproduces pain in the calf. Although traditionally taught, this sign is unreliable: it is neither sensitive nor specific. It is now generally discouraged, partly because of a theoretical concern that it could dislodge a clot. It should not be relied upon to diagnose or exclude a DVT, and modern practice uses validated risk scoring and imaging instead.

Measuring Calf Circumference

Objective measurement of leg swelling is more reliable than visual estimation, so the calf circumference of both legs should be measured and compared. Using a tape measure, identify the tibial tuberosity (the bony bump just below the kneecap) on each leg. Measure both calf circumferences 10 cm below the tibial tuberosity, so that you are comparing the same point on each leg.

A symptomatic calf at least 3 cm larger than the asymptomatic side contributes one point to the two-level DVT Wells score (a points score that estimates how likely a DVT is, explained below). A difference of exactly 3 cm counts. The measurement helps to estimate how likely a DVT is, but it does not diagnose one. Measuring at a fixed point relative to a bony landmark gives a reproducible value that can be tracked over time, rather than relying on subjective ‘eyeballing’ of the legs.

Assessment of Oedema

Test for pitting oedema by pressing firmly with your thumb over a bony area for around 10–15 seconds, then releasing. Begin at the medial malleolus and work up the shin (over the tibia) until no further oedema is found, which lets you record how far the swelling extends. If an indentation (pit) remains after you release, this confirms pitting oedema. The pit forms because the pressure of your finger displaces excess interstitial fluid (the fluid between the body’s cells). In a DVT, this fluid accumulates because the obstructed deep veins raise venous pressure and force fluid out of the capillaries into the tissues.

The distribution of the oedema is an important diagnostic clue. Oedema that is confined to the symptomatic leg is consistent with a DVT, and is one of the features used in DVT risk scoring. By contrast, bilateral pitting oedema points away from a DVT. It suggests a systemic cause such as congestive cardiac failure, chronic kidney disease, liver disease with hypoalbuminaemia, or the side effects of certain medications.

Pitting Oedema of the Lower Leg SimpleMed

Image - Pitting oedema of the lower leg. After firm pressure is applied and released, an indentation remains in the skin. Oedema confined to one leg supports a diagnosis of DVT

Creative commons source by James Heilman, MD [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Peripheral Pulses and Neurovascular Status

Although a DVT is a problem of the venous system, it is good practice to check the arterial pulses of the leg. This ensures the arterial supply is intact and helps to exclude an alternative or coexisting arterial diagnosis. It is particularly important before any compression (stockings or bandaging) is applied, because compression is unsafe if there is significant arterial insufficiency. NICE advises against elastic graduated compression stockings to prevent post-thrombotic syndrome or a repeat clot after a DVT, although they can be used to manage leg symptoms. Where the pulses are reduced or compression is being considered, you would formally assess the arterial supply by measuring the ankle-brachial pressure index (ABPI) (a comparison of blood pressure at the ankle and the arm) before any compression is applied.

Palpate the two pedal pulses in each foot:

  • Dorsalis pedis pulse: felt on the dorsum (top) of the foot, just lateral to the extensor hallucis longus tendon (the tendon that lifts the big toe).
  • Posterior tibial pulse: felt just behind the medial malleolus.

Dorsalis Pedis Pulse SimpleMed

Image - Location of the dorsalis pedis pulse on the dorsum of the foot, lateral to the extensor hallucis longus tendon

SimpleMed original

Posterior Tibial Pulse SimpleMed

Image - Location of the posterior tibial pulse, felt just behind the medial malleolus

SimpleMed original

Reduced or absent pedal pulses suggest peripheral arterial disease rather than a DVT. In the rare but serious phlegmasia cerulea dolens, massive venous obstruction can raise tissue pressure enough to compromise the arterial supply. Absent pulses in a tense, blue, swollen leg are therefore an alarming finding requiring urgent vascular assessment. Also note the capillary refill time (how quickly colour returns after you press on the skin) and the temperature of the toes as a quick check of distal perfusion.

Differential Diagnosis of a Swollen Leg

A unilateral hot, swollen, painful leg has several important causes other than a DVT, and recognising them is a key part of the examination. The clinical signs of these conditions overlap considerably, so suspected DVT should be assessed using a validated diagnostic pathway, with clinical probability, D-dimer testing (a blood test for products released when a clot breaks down) and ultrasound as indicated.

  • Cellulitis: a spreading bacterial skin infection producing a hot, red, tender and swollen leg, usually with indistinct margins. A portal of entry such as a wound or tinea (a fungal infection, such as athlete’s foot) between the toes, systemic upset or fever may provide further clues. Sharply defined margins are more characteristic of erysipelas (a superficial skin infection with a raised, well-defined edge). It can mimic a DVT, but skin redness alone does not exclude thrombosis.
  • Ruptured Baker’s cyst: rupture of a popliteal cyst releases fluid into the calf, causing sudden pain and swelling that closely resembles a DVT; a history of knee arthritis is a useful clue.
  • Calf muscle injury or haematoma: a torn gastrocnemius (the large calf muscle), known as “tennis leg”, or a bleed into the calf can cause acute pain, swelling and bruising. There is usually a clear history of sudden onset during exertion.
  • Superficial thrombophlebitis: a tender, hard, cord-like superficial vein with overlying redness, as described above.
  • Chronic venous insufficiency or lymphoedema (swelling from a build-up of lymph fluid): these produce more chronic swelling and skin change, and lymphoedema is typically non-pitting in its later stages.

Importantly, bilateral leg swelling usually reflects a systemic cause, such as cardiac, renal or hepatic failure, rather than a DVT.

Risk Factors and the Wells Score

The clinical signs of a DVT are interpreted alongside the patient’s risk factors, which broadly follow Virchow’s triad, the three contributors to thrombosis:

  • Venous stasis: immobility, recent long-haul travel, recent surgery, hospital admission, or limb immobilisation in a cast.
  • Endothelial (vessel wall) injury: trauma, surgery or previous DVT damaging the vein.
  • Hypercoagulability (blood that clots too easily): active cancer, pregnancy and the postpartum period, the combined oral contraceptive pill or oral hormone replacement therapy (NICE states that the clot risk is not increased with transdermal HRT, which is absorbed through the skin), and inherited thrombophilias (inherited tendencies to clot) such as factor V Leiden.

In UK practice, when a DVT is suspected the clinical features are combined into a two-level Wells score for DVT, which estimates the likelihood of a clot and guides further investigation. Points are awarded for features such as active cancer, recent immobilisation or major surgery, localised tenderness along the deep veins, swelling of the entire leg, a calf that is at least 3 cm larger than the other side, pitting oedema confined to the symptomatic leg, dilated collateral superficial (non-varicose) veins, and a previous DVT. 2 points are subtracted if an alternative diagnosis is at least as likely as a DVT. A score of 2 or more makes a DVT likely, and a score of 1 or less makes it unlikely. If a DVT is likely, NICE advises a proximal leg vein ultrasound scan, with the result available within 4 hours if possible, and a D-dimer test if the scan is negative. If a DVT is unlikely, a D-dimer test comes first, with the result available within 4 hours, and a positive result leads to an ultrasound scan. If the scan or D-dimer result cannot be obtained within 4 hours, interim therapeutic anticoagulation (a treatment dose of a blood-thinning drug, given while the result is awaited) is offered.

Completing the Examination

Thank the patient, help them to re-dress, and wash your hands.

Summarise your findings and state whether they are consistent with a DVT.

To complete the examination, state that you would like to:

  • Calculate a two-level Wells score to formally estimate the probability of a DVT.
  • Take a focused history exploring the risk factors above, and ask specifically about symptoms of a pulmonary embolism such as breathlessness, pleuritic chest pain (sharp chest pain that is worse on breathing in) and haemoptysis (coughing up blood).
  • Record a full set of observations (including respiratory rate and oxygen saturations) to screen for a PE.
  • Request a D-dimer blood test where appropriate. A normal result helps to exclude a DVT in a patient with a low pre-test probability (a low chance of a DVT before the test), but it is non-specific and can be raised by infection, inflammation, malignancy and pregnancy.
  • Arrange a proximal leg vein Doppler (compression) ultrasound (an ultrasound scan of the leg veins), which is the imaging investigation of choice for confirming a DVT. When a DVT is likely, NICE advises that the result should be available within 4 hours if possible.
  • If the pedal pulses are reduced, or compression stockings or bandaging are being considered, measure the ankle-brachial pressure index (ABPI) to confirm an adequate arterial supply before they are applied.
  • Send routine bloods including a full blood count, urea and electrolytes and coagulation screen, and consider further investigation for an underlying cause (such as an occult malignancy) where clinically indicated.

Quiz

Preview the Deep Vein Thrombosis (DVT) OSCE Examination quiz

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