Lung Ultrasound has Come a Long Way

Lung US and pneumonia - slider

The old-fashioned portable chest X-ray is still the preferred way of documenting pneumonia at the bedside. Although more cumbersome, CT scans are also frequently employed for more definitive diagnosis, esp. in the ER or the ICU setting.

Historically, ultrasound of the lungs (LUS) was always problematic as the sound waves do not penetrate the air-filled spaces well. It was always a very useful diagnostic tool for localizing pleural fluid and for guiding a drainage procedure but did not get much use above the diaphragm for other pathology.

A recent review article makes a case for a much broader use of LUS, specifically for diagnosing pneumonia. There are the obvious theoretical benefits of portability and safety that US has over X-ray based technologies. But how does it stack up compared to SoC techniques, what is the reproducibility of findings, and how much training is required?

Interestingly, LUS does extremely well in comparative studies. Compared to CXR or CT-scans or a discharge diagnosis of pneumonia, LUS findings were in excellent agreement with those standards. LUS performed on par with CT scans, and it was often more reliable than the time-honored portable A-P chest X-ray.

This may be surprising but we need to remember how much US technology has advanced in the last 2 decades. What makes it so appealing in addition to its reliability and safety is the fact that it can be used sequentially without any concerns for patient discomfort or incurring radiation exposure for patient or operator.  It seems to be an excellent tool to gauge prognosis.

The article does not address the training needs in much detail but this would not seem to be a major hurdle.

There is another consideration, not mentioned in the article. The field of ID is one of a few subspecialties that does not have a procedure to its name. As is well known, purely cognitive skills don’t get much respect, they certainly are not reimbursed like a procedural skill.  It is a major reason why ID physicians find themselves consistently on the bottom rung of the comparative salary structure for subspecialties.  Not having a scope to look, or a needle to biopsy or to tap fluid, with technicians only allowed to do a Gram stain for a delayed “early” diagnosis, ID is a very unattractive specialty from the financial perspective. It is not a great choice for a potential fellow with significant student loans.

It is unclear where IDSA stands on this issue but I suggest that ID programs start training fellows in LUS.  And once you are at it, have a look below the diaphragm as well, for a liver or a splenic abscess. Your overworked radiology colleague will thank you for taking off some of his workload…

 

Publication
Schenk E. Ultrasound in the diagnosis and management of pneumonia. Curr Opin Infect Dis 2016, 29:223

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