Point-of-Care Ultrasound Techniques for the Small Animal Practitioner. Группа авторов

but less reliable in cats because of more interposing feline lung in between the heart and diaphragm. However, most clinically relevant pericardial effusion is detected in both dogs and cats at the DH view (Lisciandro 2016a) (see Figure 6.11 and Chapter 39). Pneumothorax in either species is another reason for the inability to view the “cardiac bump.”

Always look cranially past the diaphragm into your patient's thorax for pericardial effusion, pleural effusion, and deep lung pathology along the diaphragmatic–pulmonary interface (see Chapters 18, 22, and 23) and use TFAST pericardial site views and Vet BLUE to confirm, refute and support findings at the FAST DH view.

Figure 6.9. Images showing various anatomic features at the DH view. None of these images are positive for free fluid and only (F) is labeled. Compare these images to those labeled in Figure 6.8. In (A) the gallbladder is expected to be in close proximity to the diaphragm. Note the mirror image of the gallbladder into the thorax. In (B) the caudal vena cava is seen in the far‐field as two hyperechoic bars, one as its near wall and the other as its far wall (see Figure 6.11 and Chapters 7, 26 and 36 for greater CVC detail). In (C) another image of the canine gallbladder is shown in close proximity to the diaphragm. (D) shows an anechoic triangulation formed by the CVC as it traverses the diaphragm that should not be mistaken for free fluid. A‐lines are seen past the CVC's far wall due to the dry lung against the CVC. In (E) the gallbladder appears bilobed in the cat and in the near‐field is robust falciform fat (see Chapter 39 for more detail). In (F) with the probe directed near parallel to the sternum, the heart (“Heart”) and its left ventricle are clearly in view and may be interrogated. The liver appears homogeneous as expected and is labeled “Liver” with it mirrored on the other side of the diaphragm due to mirror image artifact common at the DH View. Note how consistent the diaphragm is within the images as a landmark for proper DH view image acquisition.

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

Figure 6.10. Variety of typical positive studies at the DH view. In (A) free fluid is apparent in the near‐field to the gallbladder. In (B) similarly free fluid is in the near‐field to the gallbladder. In (C) free fluid separates the liver from the diaphragm. In (D) there is a smaller abdominal effusion present separating the liver from the diaphragm. In (E) the same type of positive as in (D) is shown but with an even smaller volume. Note the probe is rocked cranial enough to get the diaphragm at the xiphoid, which is good practice for the DH view. In (F) the liver lobes are separated from one another due to the abdominal effusion. Note how consistent the diaphragm is within the images as a landmark for proper DH view image acquisition.

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

Figure 6.11. The “cardiac bump” at the DH view. In (A) the apex of the heart is indenting the diaphragm and in real time can be seen clearly beating against the diaphragm. In (B) a heart is superimposed to give a better idea of orientation. The arrows point out the near and far wall of the caudal vena cava (CVC). In (C) the heart is unlabeled with the left ventricle and left atrium both in view as well as the mitral valves with the same image labeled in (D) and the heart is positioned similar to the pictorial of the heart in (F). This cardiac orientation is really important to learn because the heart is generally more sonographically accessible than transthoracic TFAST pericardial site views and its echo views in respiratory distressed patients. In (E) is the unlabeled heart against the diaphragm and labeled with the addition of an overlay of the cardiac orientation in (F). Note how consistent the placement of the diaphragm is within the images as a landmark for proper DH view image acquisition. CVC, caudal vena cava; DIA, diaphragm; LA, left atrium; LIV, liver; LV, left ventricle; RA, right atrium; RV, right ventricle.

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

Following interrogation of the pleural cavity, pericardial sac, and lung along the diaphragmatic–pulmonary interface, along the same longitudinal plane of the “cardiac bump,” look for the CVC, making sure depth is adequate as the CVC is the deepest structure at the DH view (Figure 6.12).

      If the CVC is not seen, look for it while you rock slowly back to your starting point, making sure you are on a longitudinal plane on midline and immediately caudal to the xiphoid.

      The CVC is reliably imaged with experience and should be characterized where it traverses the diaphragm, searching for the small white line in the near‐field and the longer white line in the far‐field paralleling one another and representing the near and far walls of the CVC, respectively. The lines that extend beyond the CVC's far wall are in fact A‐lines created when aerated (dry) lung (most common) is immediately against the far wall or possibly in the presence of pneumothorax (far less common) (see Figure 6.12).

      Pearl: Excessive probe pressure caused by pushing the probe into the patient's abdomen can distort the CVC, resulting in its flattening and false assessment (Darnis et al. 2018).

       Typical DH Positives

      The classic intraabdominal positives at the DH view are usually seen while fanning away from the tabletop in the following locations: the near‐field to the gallbladder, between the divisions of the liver lobes, between the liver and the diaphragm, and between the liver lobes and the falciform ligament and fat. In the near‐field, the falciform ligament and fat, which can be robust even in thin cats, are typically hyperechoic (bright) in the near‐field, having a coarser, brighter echotexture (hyperechoic) relative to the liver (see Figure 6.10 and Chapter 39).

      The most common AFAST positive views in low‐scoring AFS 1 and AFS 2 bluntly traumatized dogs and cats, clinically normal adult dogs and cats, and juvenile puppies and kittens are the nongravity‐dependent DH and CC views over the most gravity‐dependent HRU and SRU views (Lisciandro et al. 2009, 2015, 2019). Moreover, the umbilical HRU and SRU views are rarely the only positive view(s) among different subsets of dogs and cats (Lisciandro et al. 2009, 2015, 2019; Romero et al. 2015). Thus, pay special attention to the presence of anechoic triangles (free fluid) while fanning through liver lobes (see Figure 6.10).