This case illustrates a number of risk factors for the development of thrombi ("blood clots") in the deep veins of the legs - advanced age, smoking of cigarettes, systemic infection and bed rest. Other important risk factors include surgery, cardiac failure and cancer. One of the dreaded complications of venous thrombi is that they may dislodge and travel in the bloodstream to impact in pulmonary arteries (pulmonary embolism). Small emboli may have no symptoms, intermediate sized emboli may cause areas of infarction (dead lung tissue), as in this case. Massive emboli can obstruct flow through the main pulmonary artery and result in sudden death.