Venous thromboembolism

Any injury, such as a surgical operation, causes the body to increase the coagulation of the blood.

Simultaneously, activity may be reduced. There is an increased probability of formation of clots in the veins of the legs, or sometimes the pelvis, particularly in the morbidly obese patient. A clot which breaks free and floats to the lungs is called a pulmonary embolus, a very dangerous occurrence.

Commonly, blood thinners are administered before surgery, to reduce the probability of this type of complication.