Deep venous thrombosis

When blood clots in a vein which prevents blood from returning to the heart, then blood accumulates in the leg leading to swelling and pain

Blood flows from the heart to the feet through the arteries. Once in the foot, it returns to the heart through two large veins and capillaries. It then flows to the lungs where it is oxygenated. When blood clots inside a vein, it cannot return to the heart, so this blood accumulates in the leg which makes the leg swell and hurt.

Thrombosis in a deep vein is a phenomenon that could be compared to milk when it turns into yogurt, i.e. blood solidifies which hinders normal circulation.

When a venous thrombus breaks loose and moves away from the vein wall where it formed, it will eventually end up in the lungs, given that the blood in the veins always travels towards the heart, and then to the lungs through the pulmonary arteries. Once it reaches the lung, it obstructs the inside of one or more pulmonary arteries, and this is called pulmonary embolism (PE).

The most common location where a venous thrombus forms is in the deep veins of the legs. The symptoms are normally pain and swelling of the affected leg.

This is called deep vein thrombosis (DVT) because it affects the deep, but not the superficial veins of the limbs. Thrombosis may also be found in the veins in the arms or in some of the internal organs