Peripheral Venous Testing and Interpretation
Peripheral Venous Testing and Interpretation
This domain tests lower-extremity venous duplex for deep vein thrombosis (DVT), valvular incompetence, and venous hemodynamics.
Core rules
- DVT diagnosis relies on gray-scale compression. A normal vein collapses completely; acute thrombus is hypoechoic, noncompressible, and may dilate the vein. Chronic thrombus is echogenic, retracted, and may recanalize with collaterals.
- Interrogate the common femoral, femoral, popliteal, and calf veins, including posterior tibial, peroneal, gastrocnemius, and soleal veins. Compress in transverse every 1-2 cm; use color and spectral Doppler for flow, phasicity, and augmentation.
- Normal spectral flow is phasic with respiration and augments with distal compression. Continuous flow suggests proximal obstruction; absence of augmentation suggests distal obstruction.
- Reflux criteria: reverse flow >0.5 s in superficial veins, >1.0 s in deep veins, and >0.35 s in perforators. Document valve closure and reflux duration.
Worked example
A popliteal vein is noncompressible, dilated, and shows no phasicity; the ipsilateral calf is swollen. This is acute popliteal DVT. Compression is the key finding; color filling defects alone are less reliable. Extend the examination to the calf and iliac veins as clinically indicated.
Traps
Do not mistake an artery for a vein, skip calf veins, or rely on augmentation alone. A partially compressible chronic vein is not acute DVT. Severe edema can limit compression; document limits and use alternative findings.