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When the sound beam passes through a fluid‐filled structure, such as the gallbladder, urinary bladder, fluid‐filled stomach, eye, or a cyst, ultrasound waves do not become as attenuated as the neighboring waves passing through more solid tissues to either side of the structure. Therefore, the tissues on the far side of the fluid‐filled structure appear much brighter than the neighboring tissues at the same depth. Acoustic enhancement is obvious, looking past the fluid‐filled gallbladder and urinary bladder (Figure 3.3). On the other hand, by realizing how the artifact is formed, the acoustic enhancement artifact can be useful to the savvy sonographer in determining if a structure of interest is fluid filled (brighter through the far‐field having acoustic enhancement) or soft tissue (lacking acoustic enhancement) (Penninck 2002) (see Figure 3.3).

Figure 3.3. Acoustic enhancement artifact. Because there is less attenuation when sound moves through fluid, the area distal to a fluid‐filled structure will appear hyperechoic (brighter or whiter) to the surrounding tissue. Note the hyperechoic regions distal to the gallbladder (A) and distal to the urinary bladder (B) that are outlined with arrows (←) in (C) and by white bars in (D).