Is compression ultrasonography (CUS) the same as duplex ultrasound?

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Last updated: March 18, 2026 • View editorial policy

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Compression Ultrasonography (CUS) vs. Duplex Ultrasound: Key Differences

No, compression ultrasonography (CUS) is not the same as duplex ultrasound—CUS is a component technique within duplex ultrasound, but duplex ultrasound is a more comprehensive examination that combines compression with Doppler flow assessment. 1

Technical Distinctions

Compression Ultrasonography (CUS)

  • CUS uses only gray-scale B-mode imaging to assess vein compressibility as the primary diagnostic criterion for deep venous thrombosis (DVT). 1, 2
  • The technique involves applying probe pressure at 2-cm intervals along veins; inability to compress indicates acute thrombus. 3
  • CUS can be performed as limited protocols such as 2-region CUS (femoral and popliteal veins only) or extended CUS (ECUS, from common femoral vein through popliteal vein). 1

Duplex Ultrasound

  • Duplex ultrasound combines compression with color and spectral Doppler interrogation to evaluate both vein compressibility and blood flow characteristics. 1
  • Complete duplex ultrasound (CDUS) is the comprehensive protocol that examines deep veins from the inguinal ligament to the ankle, including calf veins (posterior tibial and peroneal). 3
  • CDUS includes spectral Doppler of bilateral common femoral veins to assess flow symmetry and color/spectral Doppler of the symptomatic popliteal vein. 3

Clinical Performance Comparison

Duplex ultrasound demonstrates superior diagnostic accuracy compared to compression-only techniques:

  • In a direct comparison study, duplex scanning achieved 100% sensitivity and 98.5% specificity versus CUS with 93.6% sensitivity and 97.0% specificity for femoropopliteal DVT. 4
  • For all thrombi including calf veins, CUS sensitivity was 95% compared to Doppler ultrasound at 76%, though CUS alone missed isolated superficial femoral vein thrombi. 2
  • If only common femoral and popliteal veins are examined with limited CUS, 30.3% of all DVT cases (isolated superficial femoral vein plus isolated calf vein DVT) would be missed. 5

Guideline Recommendations

The Society of Radiologists in Ultrasound consensus strongly recommends complete duplex ultrasound (CDUS) as the preferred diagnostic test for acute DVT rather than compression-only protocols. 1, 3

When CDUS is Available

  • Perform comprehensive CDUS from thigh to ankle with Doppler at selected sites as the standard examination. 1
  • This protocol provides better data to explain presenting symptoms and increases diagnosis of calf DVT. 1

When CDUS is Unavailable

  • Point-of-care extended compression ultrasound (ECUS) from thigh to knee is appropriate as a limited evaluation. 1
  • However, after negative ECUS, follow-up CDUS within 5-7 days is required to safely exclude DVT. 1, 3

Common Pitfalls

  • Never confuse arterial Doppler studies with venous duplex ultrasound—arterial studies assess arterial pathology and cannot detect venous thrombus. 3
  • Limited CUS protocols examining only the common femoral and popliteal veins will miss isolated superficial femoral vein DVT and all isolated calf vein DVT. 5
  • The terminology "duplex ultrasound" specifically refers to the combination of B-mode imaging with Doppler; using these terms interchangeably with "compression ultrasound" creates diagnostic confusion. 1

References

3
Guideline

Venous Duplex Ultrasound as the Preferred Diagnostic Modality for Suspected Deep Vein Thrombosis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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