Informational only. This page describes how this condition appears on ultrasound imaging for educational purposes. It is not medical advice, diagnosis, or treatment guidance.
Deep vein thrombosis is a blood clot in one of the deep veins of the leg, arm, or pelvis. It is the bread-and-butter pathology of venous duplex sonography — the imaging study most patients with suspected DVT receive first.
What it is
A DVT forms when blood clots inside a deep vein, typically in the lower extremity (femoral, popliteal, or calf veins). The clinical concern is twofold: the clot can obstruct venous return, causing leg swelling and pain, and a fragment can break off and travel to the lungs as a pulmonary embolism (PE). About 900,000 cases of venous thromboembolism (DVT plus PE) are diagnosed in the United States each year, with roughly 100,000 attributable deaths.
DVT risk factors group into the classic Virchow’s triad: venous stasis (immobility, long-haul travel, hospitalization), endothelial injury (surgery, trauma, indwelling lines), and hypercoagulability (genetic factors, malignancy, hormonal contraceptives, pregnancy).
How it appears on ultrasound
Venous duplex ultrasound is the first-line imaging study for suspected lower-extremity DVT and is recommended over CT or MRI by ACR Appropriateness Criteria. The exam combines B-mode imaging with color and spectral Doppler, performed in segments from the common femoral vein down through the popliteal vein and tibial veins.
The defining sonographic finding is non-compressibility. A normal vein collapses fully when light pressure is applied with the transducer; a vein containing thrombus does not. A complete venous duplex protocol applies compression at standardized intervals — typically every 1 to 2 cm along the deep system — and documents whether each segment compresses.
Other findings reinforce the diagnosis: echogenic intraluminal material on B-mode (fresh clot is often hypoechoic and may be missed without compression testing), absent or reduced color flow within the vein, and loss of normal respiratory phasicity on spectral Doppler. Acute DVT typically shows venous distension and homogeneous low-level echoes; chronic clot is often more echogenic, less distensible, and may show recanalization channels.
Calf vein thrombosis carries a lower embolic risk than proximal DVT and is sometimes followed with a repeat ultrasound at five to seven days rather than treated immediately. Ultrasound’s portability and lack of contrast or radiation make repeat imaging practical — a meaningful advantage over CT venography.
Which specialty images it
Vascular sonography is the primary imaging discipline for DVT. Vascular sonographers (RVT-credentialed) perform venous duplex studies in dedicated vascular labs, hospital imaging departments, and increasingly at the bedside in emergency departments and ICUs. Some general sonographers cross-train into vascular work; the vascular specialty page covers the credential and scope.