​A vascular duplex ultrasound is a non-invasive imaging test used to assess blood flow in the arteries and veins. It combines traditional ultrasound, which produces images of the blood vessels, with Doppler ultrasound, which measures the speed and direction of blood flow. This test helps diagnose conditions such as narrowing or blockage of arteries, blood clots, aneurysms, varicose veins, and problems with dialysis access fistulas or grafts. During the scan, a small handheld probe is placed on the skin with ultrasound gel, allowing the vascular scientist to examine the vessels in real time without the need for injections or radiation. A vascular duplex scan is safe, painless, and commonly used to guide diagnosis, treatment, and follow-up of vascular conditions.