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The liver's venous system can appear as anechoic sharp triangulations like free fluid. The venous system as a general rule is not obvious in normalcy when patients are examined in lateral, sternal and standing positions. This false positive is easily avoided because most free fluid is not as linear as the venous system, and the venous system in most instances can be traced and seen branching (see Figure 6.12) (see Chapter 8). Color flow Doppler may be used to distinguish the venous system from free fluid but is rarely needed. Hepatic veins are differentiated from portal veins in a couple of ways. First, portal veins have brighter, more echogenic (hyperechoic) walls when compared to hepatic veins and thus portal veins often appear as hyperechoic (bright white) equal [=] signs (see Chapters 8 and 39). Hepatic veins are darker walled sonographically and are generally traced as they drain into the CVC, especially when there is hepatic venous distension (see Figure 6.12F and Chapters 7, 20, and 36).

Figure 6.16. Additional examples of pitfalls at the DH view. (A) and (B) are the same image unlabeled and labeled. The gallbladder is bilobed, most commonly seen in cats. It appears similar to free fluid but through interrogation by fanning through the gallbladder in both directions, the rounding of the hyperechoic gallbladder wall differentiates it from free fluid. (C) and (D) are the same image unlabeled and labeled. Note the caudal vena cava (CVC) can mimic pleural effusion at the level of the diaphragm; however, the dynamic changes in CVC diameter with respiratory and cardiac cycles and its A‐lines through the far‐field differentiate the CVC from pleural effusion. In (E) and (F), the same image is unlabeled and labeled with a circle indicating the stomach wall that is anechoic and can mimic free fluid (and its associated edge shadowing artifact; see Figure 3.2). Note how consistent the diaphragm is within the images serving as a landmark for proper DH view image acquisition, which in and of itself (the proportionality shown) will prevent many DH view pitfalls. CVC, caudal vena cava; GB, gallbladder; LIV, liver; ST, stomach.

Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX.