You may have noticed my recent obsession with all things respiratory. Seeing and personally experiencing a lot of LRTIs recently.
A few weeks back Cliff Reid @resus.me put up this article for discussion: Lung US for pneumonia in ED, Emerg Med Journ 2012. Which suggests that US is at least as good as an CXR for the early diagnosis of pneumonia and actually picked a few more when the CTs were compared as a gold standard. It was a small study of 120 patients – so I thought I would look further into the literature – see what else is out there. Here is what I found:
Evaluation of lung ultrasound for the diagnosis of pneumonia in the ED. Amer Journ Emerg Med 2009
Ultrasound diagnosis of pneumonia in children. Radiol Med. 2008
Clinical application of transthoracic ultrasonography in inpatients with pneumonia. Europ Journ Clinical Investigation 2011.
Diagnosis of radio-occult pulmonary conditions by real-time chest ultrasonography in patients with pleuritic pain. Ultrasound in Med Biol 2008
It seems the Italian sonographic community have cornered the market in all things chest US in the past few years!
So in summary if you are too busy to read the articles – there are a pile of little observational studies out there that all say the same thing – US is as good as a CXR, maybe a little more sensitive for showing pneumonia / consolidation. It is very likley to be better than the clinical examination – however that is not how this works.
If you hear something or are unsure – then use the probe as the next “test” – if you get a positive then likley you have found a pneumonic process. You can treat this as clinically appropriate, and still get a CXR if necessary later. However, especially in kids – do you really need to irradiate them? Or can we use clinical progress, repeat US and still achieve the same ends?
I suspect those of us who grew up on CXR diagnosis will be more comfortable seeing a positive, or a negative – however if you look in the numbers – CXR has a significant false negative rate in pneumonia (especially early in the disease) – so should we be so comfortable? I think this is one of those common biases in Medicine – we attribute too much weight to a familiar test, even though we know it might be steering us in the wrong direction. We like yes/no, black/white answers – and believe in CXR as it has been drilled into us from day 1 of Med School!
This is a great example of US being an “extension of the clinical examination” rather than a “test” – after all, with US you are looking at the sound that you might be able to hear with your stethoscope and ears. I suspect in 10 years this will be something we teach in Medical Schools – the old look, listen, feel, percuss with have “scan” added to the end of the exam.
Love to hear your thoughts