How can an examiner be certain a vein is thrombosed on duplex examination?

• A. The vein collapses during compression
• B. The adjacent artery collapses or snaps when pressure is applied but the vein remains visible
• C. The vein shows continuous holographic Doppler signals
• D. Color Doppler shows persistent flow in all segments

Answer: (B)

Compression findings are key in identifying venous thrombosis on duplex. In an acutely thrombosed vein, the intraluminal clot makes the vein noncompressible—so when you apply gentle pressure with the transducer, the vein stays visible and does not collapse, while a nearby artery (which is not thrombosed) will compress or “snap” under the same pressure. This contrasting response—noncompressible vein with a compressible artery—is a classic sign of a thrombus. If the vein collapses with pressure, that argues against thrombosis, and persistent flow on color or continuous Doppler in all segments would also suggest patency or partial thrombosis rather than a complete acute blockage.