Dr Achyut Patil explains how the investigative test call Colour Doppler can help identify problems associated with the lower limbs..The Colour Doppler ultrasound is a non-invasive test. It estimates the amount of blood flow by bouncing high-frequency sound waves (ultrasound) off the red blood cells. Colour Doppler imaging allows better visualization of vertebral arteries compared to conventional ultra sonography..A Doppler ultrasound on the lower limbs helps diagnose the following conditions:.Blood clotsPoorly functioning valves in your leg veins, causing blood or other fluids to accumulateA blocked arteryDecreased blood circulation into your legsBulging arteries (aneurysms)Varicose veins.Diagnosis.A normal reading signifies no narrowing or other abnormality or clots. The size and position of veins are normal and there is normal blood flow in blood vessels that supply oxygen and nutrients..An abnormal reading is denoted by a high pitched or turbulent sound or an irregular flow may indicate the exact location where an artery is blocked or narrowed and the presence of varicose veins. It also identifies if the blood vessels that supply oxygen and nutrients to a fetus are abnormally increased or decreased..Relaibility.The technological advances in ultrasonography have resulted in them being increasingly used as a diagnostic device..Performing the test.The patient is asked to lie down and a special gel is applied to the area to be examined. The gel allows better transmission and reception of the ultrasound waves. The ultrasound wand is placed and moved on the skin. There may be some mild discomfort. The information is sent to the computer and images are seen on the monitor. During the test, a whooshing sound, which is the sound that the ultrasound machine makes to represent your blood moving through your body, is heard..Advantages.Colour Doppler examination is non-invasive (no needles or injections used)It is widely available, easy-to-use and less expensive than other imaging methods.Colour Doppler is extremely safe and does not use any ionizing radiation.Colour Doppler examination presents a clear picture of soft tissues that do not show up well on x-ray images..Dr Achyut Patil is the Head of the Radiology Department at Chellaram Diabetes Institute, Pune.