Chief and common cause of pulmonary embolism is:

Correct option is D

The most common and chief cause of pulmonary embolism (PE) is venous thrombosis, particularly deep vein thrombosis (DVT) originating from the deep veins of the lower extremities. When a part of this thrombus dislodges, it travels through the venous system to the right side of the heart and then into the pulmonary arteries, causing a pulmonary embolism.

This condition is part of the venous thromboembolism (VTE) spectrum, which includes:

• Deep vein thrombosis (DVT)
• Pulmonary embolism (PE)

Major risk factors for venous thrombosis include:

• Prolonged immobility
• Surgery (especially orthopedic)
• Cancer
• Oral contraceptives
• Hypercoagulable states

Explanation of Each Option:

• (a) Fat emboli –
  Occurs after long bone fractures, especially femur, but is a rare cause of pulmonary embolism. Not the chief or common cause.
• (b) Air emboli –
  Seen in cases like central line insertion or trauma, but it is uncommon and not the primary cause of PE.
• (c) Septic emboli –
  Arise from infected thrombi, such as in endocarditis, and can cause embolism, but these are less common and secondary causes.
• (d) Venous thrombosis –
  This is the leading and most frequent cause of pulmonary embolism, especially from lower limb DVT.