Consolidation vs Infiltrate vs Opacity on CXR

I'm having a hard time understanding the difference between consolidation vs infiltrate vs opacity on CXR. Many times they seem interchangeable.

Consolidation is alveoli filled with some sort of fluid instead of air/gas. It can be pus (Pneumonia), water (CHF), blood, or a tumor. I usually see consolidation in reference to pneumonia.

Infiltrate and Opacity also seems to be the exact same definition as consolidation. Anybody can help clarify this?

7 Answers

Infiltrate is when your alveolar spaces are filled with some sort of fluid, i.e. transudate, exudate. Consolidation is more of a measure of the texture and hardening of the lungs. But on a CXR you can't distinguish between the two. Certainly when tied to a clinical history and physical exam you can piece together what's happening more precisely, but without that a better term would be "opacification" or even just "density", as these are broader, and with less context or effect on implying disease process.

It really just depends on who is reading it. The good reports give a guess at what it could be, fluid versus CHF based on the history given in the order.

Here's a study that proves even physicians don't know what the hell infiltrate means: Is Infiltrate a Useful Term in the Interpretation of Chest Radiographs? Physician Survey Results1

Specializes in ER trauma, ICU - trauma, neuro surgical.

I'll start with a disclamer that I'm obviously not a radiologist, but I will try my best.

As you gain more experience in the ICU, I recommend getting into the habit of looking at every xray. I had no idea what I was looking at in the beginning, but after a while, you will start to get a sense of things. Ask your intensivist every chance you get to explain things and piece together images as time goes on.

Many of those terms are used interchangeably, and a radiologist will use different terms for any number of pts.

The best thing you can do to pick out what is what is to visually inspect the xray. You can see where the abnormals are. If the infiltrate is located in the bronchus or bronchioles, then "consolidation" may indicate mucus consolidation. If it is diffuse or located in the lobes, it may be more of a pneumonia (but pneumonia can certainly be located in the bronchus). The term opacity is used for fluid or effusions. If the bottom of the lung is very hazy and you can't tell the costal angle, then an effusion can be the opacity. But the term consolidation basically means "gather of." It may not be continous or "patchy." Opacities may be more of a solid, continuous abnormality. Infiltrate means something has infiltated the tissues.

So, if you can actually look at the xray and see the characteristics of the opacity or consolidation, you may get a better idea of whether or not it's mucus, fluid, or an invasive organism.

If you look at a chest xray, look at the ribs and see how they are separated. If the ribs on the right side of the xray or closer together then the ribs on the left, then the right chest has atelectasis. The atelectic tissue causes the lung to deflate and the ribs are noticeably closer. If a pt get a CXR with full inhalation and all the ribs are pretty close, then the whole chest is atelectic.

Also if the patient is a frequent flyer, check out their past x-rays and compare them with new ones.

CHF exac or pneumonia will be easily identifiable if they had a clear CXR sometime in the recent past.

Some people have odd looking x-rays with no good reason and if it's a trend across admissions, it's likely not anything acute.

As a radiologist, the answer is:

Infiltrate should NOT be synonymous with pneumonia but often is used that way by clinicians and even radiologists.

Technicallly, infiltrate is when tissue is infiltrated.... So, in the lung, there is increased density of the lung markings, or a hazy area. Once it becomes completely confluent density, with no air left, then it is consolidation. Infiltrate can be edema, pneumonia, or any process which "infiltrates" the lung. Consolidation can be the same or just atelectasis that collapses the lung.

Thanks for all the replies. I think after reading all the posts and talking to some attending docs that you shouldn't necessarily pay attention to the words used in the radiology report, but rather connect the patient's history (CHF, current fever, purulent sputum, etc) to the visual CXR to find a diagnosis. Essentially, an infiltrate, opacity, or consolidation appears to mean an abnormal process going on in the lungs, most likely r/t pnuemonia or CHF.

Is the patient oxygenating and ventilating? Is there a requirement for supplemental oxygen? Is the patient's mental status deteriorating? What does the patient look like? is there a correlating ABG?

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