Chronic Venous Insufficiency (CVI) is a progressive vein disorder that occurs when the valves inside leg veins become damaged or weakened, allowing blood to pool and flow backwards instead of returning efficiently to the heart. Symptoms often begin with leg swelling, heaviness, aching, varicose or spider veins, and skin changes such as discoloration or itching. Over time, untreated CVI may lead to complications like non-healing ulcers or infections. Diagnosis typically involves a duplex ultrasound to map blood flow and identify valve dysfunction.