CPD Short: Ultrasound assessment of the calf veins for DVT

Written by Nicki Davidson, lead sonographer. Worcestershire Acute NHS Trust

This CPD article aims to provide an overview of the ultrasound assessment of the calf veins in suspected deep vein thrombosis (DVT).

By recognising the key ultrasound findings associated with calf DVT, sonographers can aid accurate diagnosis and guide timely clinical management.

This article outlines six key points followed by five reflection prompts to enhance your expertise in detecting calf DVT using ultrasound imaging.

Clinical Presentation and Prevalence

Calf DVT commonly presents with localised calf pain, swelling, tenderness, and sometimes erythema.

Isolated calf vein DVT can account for around 50 per cent of all lower limb DVTs (Righini et al.2025).

Although evidence is limited, extension rates proximallyof up to 10 per cent and rates of pulmonary embolus of 1–3 per cent in conservatively managed patients appear consistent throughout the literature. (Horner et al. 2016).

Assessing the calf veins is especially important in patients with persistent symptoms or raised D-dimer despite normal proximal findings.

Six Key Points

1. Identification of Calf Vein Anatomy

The calf veins are small and can be deep, so correctly identifying the veins can often be a challenge. As a minimum, you will want to identify posterior tibial, peroneal, gastrocnemius, and soleal veins.

Use a systematic approach to gain confidence that you have assessed all locations.
Use the accompanying arteries as landmarks. The posterior tibial and peroneal veins are paired veins which run alongside the artery. These are considered companion veins or “venae comitantes” formation, as the pulsing of the artery helps to push the blood back up towards the heart.
Expect anatomical variation and be prepared to adjust depth/angle. Recognise normal variants such as duplicated veins, deep positioning of the peroneal veins, and prominent soleal sinuses, which may make scanning more challenging but are common anatomical patterns.
See video for location of posterior tibial and peroneal veins: https://www.youtube.com/watch?v=Dktg5tVwzAM

2. Ultrasound Technique

A high-frequency linear transducer (2-9MHz or 7-12MHz) is the probe of choice for evaluating calf veins. On completion of the proximal leg scan:

Begin at the popliteal vein and follow the vessels distally, using graded compression every 1–2cm.

Tips

Use a dedicated vascular setting on the machine
Adjust depth and focal zones for optimal vein wall visualisation
Some machines will have a penetration setting for deeper vessels/ larger legs.
Using the curvilinear probe can be useful in larger legs.
Recognising that non-compressibility=DVT until proven otherwise

3. Use of Colour Doppler and Optimisation

Normal calf veins are thin-walled, fully compressible, and demonstrate spontaneous colour filling. However, because some calf veins are difficult to compress (e.g., peroneal veins), colour Doppler is essential.
If you are struggling to identify the veins, use the colour to pick up the artery which runs along the paired veins.
As blood flow can be slow/ static when the patient is at rest, augmentation is often required. Squeezing the lower leg/ankle gently to encourage blood to move up the leg.
Check for absent or reduced flow in suspicious segments
Increase colour sensitivity for slow flow
Use power Doppler for deeper muscular veins when needed

4. Direct Signs of Calf DVT

Non-compressibility: The primary diagnostic sign; affected veins will not fully collapse with gentle pressure.
Intraluminal thrombus: Acute thrombus may appear hypoechoic; chronic thrombus becomes more echogenic.
Vein dilation: Acute DVT causes a distended vein compared with the accompanying artery.
Absent or reduced colour flow: Colour Doppler shows little or no filling within the thrombosed segment.

5. Indirect Signs of Calf DVT

Perivascular oedema: The surrounding tissues may become hyperechoic, which can indicate inflammation caused by an acute DVT.
Collateral veins: Additional vessels may appear in chronic or acute DVT. This is due to the smaller surrounding vessels enlarging to make a natural bypass around the blocked vein.
Thrombosis within the veins of the muscles: Gastrocnemius and soleal vein thromboses may be isolated, but are important as they are potential propagation sources. It is important to review how close any thrombus within these veins is to a junction with a ‘deep’ vein.

6. Limitations and Challenges

Calf DVT scanning is highly operator-dependent and often technically challenging. Things to consider:

Oedema, obesity, immobility, and patient discomfort limiting compression
Deep positioning of peroneal veins
When findings are equivocal, borderline, or visibility is limited
Document clearly and recommend follow-up (e.g., repeat scan in 5–7 days) if appropriate to local protocol.

Reflection Prompts

Reflect on the challenges faced when imaging the calf veins for suspected DVT and identify strategies to improve visualisation and confidence during assessment. Does your technique change for a person who is completely mobile compared with one presenting in bed?

Discuss the role of calf vein ultrasound in differentiating DVT from other causes of calf pain, such as Baker’s cyst rupture, muscle tear, or cellulitis. Ensure you are aware of the most common pathologies and what they look like on scan.

Reflect on cases where calf DVT findings were subtle or equivocal. What additional techniques (e.g., Doppler optimisation, patient positioning) were helpful?

Evaluate the impact of including routine calf vein assessment in departmental DVT protocols, particularly regarding early detection of distal thrombus propagation. Are you fully aware of your departmental policy? How does this relate to NICE guidelines?

Would an isolated soleal vein thrombosis be treated with anticoagulation in your department?

Reflect on the importance of team communication — to ensure appropriate follow-up, management, and escalation for distal DVT findings. Does your trust have a policy which treats distal DVT?

CPD Short: Ultrasound assessment of the calf veins for DVT

Clinical Presentation and Prevalence

Six Key Points

Reflection Prompts

Further Reading

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