V/Q mismatch: Meaning in a Radiology Report

Also written as: ventilation-perfusion mismatch, mismatched perfusion defect, VQ mismatch

A V/Q mismatch is an area of lung that gets air but little blood on a ventilation-perfusion scan, a pattern that can point to a blood clot.

What it means

A V/Q scan compares two sets of lung pictures. For ventilation (V), you breathe in a radioactive gas or mist that shows where air reaches. For perfusion (Q), a tracer injected into a vein shows where blood flows. Normally the two pictures match. A mismatch is an area that gets air but little or no blood, so the pictures differ.

When it matters

The classic cause of a mismatch is pulmonary embolism, a blood clot blocking an artery in the lung. The radiologist weighs how many defects there are and how large, and often states a probability. Matched defects, where air and blood are both reduced, usually point to lung disease such as COPD or pneumonia instead. Old clots and some rarer conditions can also cause a mismatch. So results are read together with your symptoms and other tests.

Questions to ask your doctor

How many mismatched areas were found, and how large are they?
Could this be from an old clot rather than a new one?
Do I need a CT scan or other tests to confirm the result?

General information, not medical advice. What a finding means for you depends on your symptoms, your history and the images themselves, so talk your results through with a doctor.