Artifacts are a fundamental component of ultrasound imaging, for instance, the sonic shadow in the case of gallstones. However, the value of the method lies in its visualization of parenchyma, for instance, that of the liver. On chest ultrasonography, the presence of artifacts permits the diagnostician to confirm or rule out a pneumothorax (the absence of gliding, a large number of horizontal reverberations, and lung point) with a high accuracy. However, comet tails are found in a large number of interstitial lung processes, ranging from lung edema of various causes to fibrosis. One sees that the lung is diseased, but the spectrum of the etiologic characteristics of disease is very wide.