The examination is performed with the patient supine. The head of the bed is elevated 30° to facilitate venous pooling of the lower extremity. The extremity is externally rotated. Duplex or color-flow scanning is performed utilizing a linear transducer in the 5–7.5 mHz range. In patients with an elevated body mass index, a lower frequency transducer such as a 2.5–3.5 mHz is used to facilitate visualization of deeper structures. The transducer is placed in the groin, inferior to the inguinal ligament, to identify the common femoral vein. This structure lies medial to the common femoral artery. Transverse plane compressions using the transducer are performed at 1–2 cm intervals along the vein and images are obtained. Compression images should reveal complete compression of the vein being interrogated. Further, the vein lumen should completely compress, and the walls should coapt. Adequate compression is being applied if the adjacent artery diameter is reduced. If proximal compression cannot be performed, the Valsalva maneuver can be utilized to observe if there is respiratory phasicity or augmentation. With Valsalva, a normal vein expands to more than 50 % of its baseline diameter. Further if there is a proximal deep venous thrombus, the Valsalva maneuver will decrease vein dilatation.

The transducer is oriented so that a longitudinal image can be obtained. This view will afford comprehensive images of flow characteristics of the vein being interrogated. Normal venous flow characteristics include spontaneous flow and phasic flow. Additionally, during compression, augmentation of the Doppler signal is demonstrated. Color imaging is used with distal compression to obtain augmentation measurement.

The examination begins with complete interrogation of the common femoral vein and saphenofemoral junction, as well as the proximal deep femoral vein. This sequential compression is performed along the common femoral vein, with continuation into the femoral vein and popliteal vein. At Hunter’s canal, patient positioning may need to be changed, by either placing the patient in the lateral decubitus or prone position to aid in visualization of the infrapopliteal venous system. Incidental findings may be evident at the popliteal fossa. These include Baker’s cyst, hematoma, abscess, or edema. Attention is now turned towards the calf veins. As previously described, the infrapopliteal venous system consists of three paired sets of veins, (anterior tibial, posterior tibial, and peroneal) as well as the soleal sinuses and the gastrocnemius veins.

Evaluation of the infrapopliteal veins is performed in most centers from the foot and then traveling proximally with the transducer. Alternatively, sequential venous segmental compression should be performed as one travels distal towards the foot. Spectral analysis is performed with plantar flexion or squeezing the calf to assess veins with sluggish flow. Further, these maneuvers can facilitate patency of the iliac venous system. If possible, repositioning of the patient with the lower extremity in a dependent position may facilitate imaging. Despite these additional maneuvers, it is still quite common to inadequately compress and/or visualize the entirety of the calf veins. This is due to the small caliber of the calf veins, patient edema, body habitus, and inexperience of the examiner.

The great and small saphenous veins are interrogated throughout their course, imaged, and sequentially compressed in utilizing the techniques previously described.