Here is a quick refresher for lung surface anatomy. Here we are able to see the surface anatomy for the right and left upper lobes, right middle lobe, and left lower lobes. In the next section, we explain the 6 point lung ultrasound exam we use.
Abbreviations: RUL: Right Upper Lobe, RML: Right Middle Lobe, RLL: Right Lower Lobe, LUL: Left Upper Lobe, LLL: Left Lower Lobe
We will be using lung ultrasound to look for pathology that affects the pleura, alveoli, and interstitium.
The parietal pleura interfaces with the visceral pleura, creating a sliding motion as we breathe. We will later discuss how this “lung sliding” motion is a very important finding during an ultrasound because it can rule out disease processes such as pneumothorax.
Alveoli exist in lobules that are subdivided by interlobular septa. The septa anchor into the visceral pleura to stabilize the lobules. When these areas fill with fluid due to consolidation or pulmonary edema, we see various artifacts manifest on ultrasound.
It is important to remember that ultrasound waves are completely scattered and attenuated (absorbed) by the air that fills healthy alveoli. Thus, if the patient has normal lungs, you should not be able to see the texture of the parenchyma (lung tissue) during your scan.
However, in certain pathologies like interstitial lung edema, the accumulated fluid in the interlobular septa results in lung ultrasound artifacts known as “B-lines.” And as lung disease progression worsens further, you may start to even see entire consolidation of the lung on ultrasound. We will discuss this further in the pathology section of this post.