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.

Various: Typically a pulmonary embolism will show defects on the perfusion portion of a ventilation/perfusion scan (also know as a vq).

Mismatch: Normal ventilation and decreased perfusion, that is normal air but blocked blood flow by clots.

Sometimes unclear: The findings of a ventilation perfusion scan can sometimes be non-specific and unhelpful. The better way to confirm a pe now is with a spiral ct scan of the lungs with infusion.

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.