A Doppler ultrasound estimates the blood flow through vessels by transmitting high-frequency sound waves throughout the body, states Mayo Clinic. It estimates how fast blood flows through the vessels by determining the change of pitch the movement registers.
A Doppler ultrasound diagnoses conditions such as bulging arteries, blood clots, defective valves in the leg veins, blocked arteries and decreased blood circulation in the legs, explains Mayo Clinic. It also pinpoints congenital heart disease, a narrowed artery and heart valve defects. The Doppler ultrasound also searches for artery injury and observes treatments to the arteries and veins, and it is used as a less invasive procedure than venography and arteriography.