[doctoring]

Ultrasound has a ton of untapped utility and is a fantastic medical imaging modality. Like you said, the equipment is cheap and portable (can be pocket sized, even!). It’s near instantaneous, allowing you to image in real time. You can even measure blood flow velocity and see other physiology. (I could go on!)

But its great advantage over x-ray and CT, which is that it doesn’t use ionizing radiation, is also its greatest weakness. Ultrasound uses sound waves, of course, which unfortunately simply cannot travel very far in the body, and (critically) do not travel well across certain interfaces. One such interface is with air. Sound waves travel through your chest wall fine but on arriving at the lung... they just sort of fizzle out. Very little sound continues, and even less comes back to the transducer as meaningful signal.

So ultrasound is unfortunately very poor at seeing lung tissue. (It can show us some secondary findings of pulmonary disease in the lungs, such as fluid collecting in the thoracic cavity [a pleural effusion], but that’s yet another non-specific finding.)

[haldujai]

Not entirely true.

Ultrasound actually has pretty good sensitivity for pneumonia (88%) and even higher if you look at the “difficult” cases requiring CT in the Cochrane review I link to below.

While the fundamentals of what you say are correct, consolidation by definition is the build up of fluid which is very well depicted by ultrasound. For a predominately peripheral airspace disease like COVID-19 ultrasound should theoretically be very sensitive.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5279077/

[doctoring]

I wasn’t aware lung US was at this point — I’ll have to read more!