Chest X-Ray Interpretation

Chest X-Rays invariably show up in the exam, either in the VAQ or SCE sections.  At work in the ED, and in exams, I frequently hear descriptions of lung opacities on chest X-rays that invariably include the words “fluffy”, “hazy”, “patchy” and other hopelessly non-radiological, non-medical words.  Have you ever read a radiology report that says “the lungs are a bit fluffy at the bases”? I haven’t. So why do we use these words? The main reason is that we’re lazy and haven’t bothered to learn my simple technique for describing lung opacities.

As with any X-Ray description in an exam, using the correct terminology will not only make you sound more professional, but it will give you a more succinct differential diagnosis.  This article will also help you in your day-to-day work, not only by helping you make more accurate chest X-Ray diagnoses, but also by improving the standard of your documentation and referrals. (Click on the images to enlarge them).

There are only 3 things in your lungs, so opacities in the lung fields on Chest X-Rays can only be one of these 3 things

1) Blood Vessels (which run through the intersitium)
2) Interstitium (the actual solid lung tissue)
3) Airspaces (the majority of which are alveoli)

Blood Vessel Opacity:
Not much can happen to these, they can either:
1) Distend: which shows as pulmonary venous congestion

congestion1 congestion2
2) Get blocked: which shows up as pulmonary infarcts



2) Alveolar (airspace) Opacity:
Xray Appearance: diffuse opacity with  ill-defined edges, (like cotton wool)
Causes: There’s only a few things that can fill your alveoli up and make them radio-opaque:
1) Inflammatory Exudate (pus)
Eg Pneumonia
2) Pulmonary Oedema – as the fluid leaks out the vessels into the surrounding tissue
Can be:
3) Blood:
Eg Goodpastures, CF
Neoplastic Cells
Ca lung (usually interstitial, but can fill airspaces)

alveolar1 alveolar2

3) Interstitial Opacity
Xray Appearance: Linear, streaky, Kerly A/B
Causes: There’s even fewer things that can infiltrate your interstitium!
1) Acute
Eg: Pulmonary oedema
2) Chronic
a. Fibrosis (hence the term “interstitial lung disease”)
b. Sarcoid
c. Lymphangitis
d. Pneumonocoiosis

intersitial1 intersitial2

So there you have it, the simple, easy to remember way to describe chest X-rays that will not only make your diagnoses more accurate, but make you sound like you know what you’re talking about, at work and in the exam.

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