What does blood clot in the lungs (pulmonary embolus) show on ventilation perfusion scan?

Lack of blood flow. A ventilation perfusion scan is a test for a blood clot in the lungs, or pulmonary embolism. If there is a blood clot, an area of the lung will not be perfused, but will be ventilated, and therefore a mismatch will be seen.
Typical. The typical finding is a mismatch between ventilation and perfusion, however in people with small clots or underlying pulmonary disease the findings are the scan are not always clear.
Mismatch. Normal ventilation and decreased perfusion, that is normal air but blocked blood flow by clots.
Various. Typically a pulmonary embolism will show defects on the perfusion portion of a ventilation/perfusion scan (also know as a vq).