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

“unremarkable” or “abnormal” to capture the case for additional imaging and confirmatory testing. Over time, more interpretative skills may be gained through experience and accompanied by additional POCUS study and training.

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

      The classic AFAST DH view is in fact part of AFAST, TFAST, and Vet BLUE because it provides a huge amount of clinical information, including structures within both the peritoneal and pleural cavities.

      The DH view begins with longitudinal placement of the probe with the probe marker towards the patient's head immediately caudal to the xiphoid process.

Figure 6.8. The DH view in a dog. In (A) is shown where the probe is placed immediately caudal to the xiphoid (top image) and directed cranial (arrow) in middle and bottom images with overlay of heart, diaphragm (curved white line), gallbladder (black oval), CVC (black rectangle with white line as near wall and longer white line as far wall). In (B) inverted correlating lateral thoracic radiographs in the top image, unlabeled, the middle image having arrows for direction of the ultrasound beam (scanning plane), white circle for probe placement, and bottom image with overlay of structures including the gallbladder, diaphragm, CVC, including A‐lines beyond its far wall through the far‐field from aerated (dry) lung, and the heart with ventricles as triangles and atria as circles. In (C) is CT for another correlation of the anatomy of the DH View. (D) and (E) are unlabeled and labeled ultrasound images of the DH view's anatomical features. Note the consistency of where the diaphragm is located in each of the ultrasound images. CVC, caudal vena cava; DIA, diaphragm; GB, gallbladder; Hrt, heart; HVD, hepatic venous distension; LIV, liver. Computed tomography courtesy of Dr Daniel Rodriguez, VETTEM, and Dr Jesús Paredes, CVM, Mexico City, Mexico.

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

The probe is then directed far more cranially than most sonographers expect (Figure 6.8). Depth should be adjusted so that the diaphragm courses through the distal two‐thirds of the image on the screen so that the near‐field is two‐thirds abdomen and the far‐field one‐third thorax. This allows for adequate screening of both the abdomen and thorax.

      The gallbladder, if not in view, is found by fanning toward the table top (when in right lateral recumbency) because of its location right of the midline in dogs and cats (further right in cats). In normalcy, the canine gallbladder is easy to find because it is generally much closer to midline than the more laterally located feline gallbladder (see Chapter 39).

      The mantra for the DH view is to have a general overview of three structures – the gallbladder, “cardiac bump”, and caudal vena cava – before starting the fanning, rocking, and returning. Start with a depth of 7–8 cm for cats and small dogs to 10–15 cm for medium to large dogs and then decrease depth as indicated.

Once the gallbladder is in view, then in a sequential way specifically interrogate the following.

       The abdominal cavity for free fluid by fanning through the gallbladder and adjacent liver in both directions, followed by…

       Rocking the probe toward the sternum to best image the “cardiac bump” where the muscular apex of the heart is very near or immediately against the diaphragm for pericardial effusion, and then…

       Imaging along the diaphragm for pleural effusion, and lung pathology along the pulmonary–diaphragmatic interface.

      In this same plane or close by, and making sure that the probe is immediately against the xiphoid, look for the CVC as it traverses the diaphragm present in both canines and felines. The CVC is recognized by the two bright white (hyperechoic) bars that make up the near wall (short bar) and far wall (long bar) with reverberation artifact (A‐lines) extending through the far‐field dependent on depth and the presence of dry lung in that patient.

      The steps taken during the AFAST DH view are as follows.

       The gallbladder wall and its shape should be noted and the gain adjusted based on the echogenicity of its luminal contents. In normalcy, the homogeneous anechoic (black) echogenicity of bile should approximate what would be expected for most types of free fluid.

       In dogs, the gallbladder reliably lies immediately against the diaphragm when positioned in right lateral recumbency; however, the gallbladder–diaphragm proximity is much less reliable in cats.

       When the canine gallbladder does not lie immediately against the diaphragm, liver enlargement should be suspected, and when the gallbladder is not located, the rule‐out list placed into clinical context should include its rupture, its displacement (diaphragmatic herniation), or the presence of gallbladder stones, mineralization, sludge, mucoceles, and emphysematous cholecystitis.

       Once the gallbladder is recognized, fanning takes place by directing the probe away from the tabletop to the patient's left, and then by fanning toward the tabletop toward the patient's right, interrogating the adjacent liver. The feline gallbladder and biliary tract differ from dogs (see Figures 8.4 and 39.4, and Chapters 8 and 39).

       By doing so, the liver and abdominal cavity are interrogated for obvious free fluid between liver lobes and between the liver and diaphragm, and the gallbladder and liver are screened for any obvious abnormalities or sonographic deviations from normal (Figures 6.9 and 6.10).

      Pearl: To perform the DH view consistently and effectively, while fanning through the gallbladder and liver, maintain the diaphragm in the distal two‐thirds of the field of view.

      Pearl: In low‐scoring benign and pathological small‐volume effusions, our research has shown the DH view as most commonly positive. These small‐volume effusions are detected between the liver and diaphragm as an anechoic stripe, and between liver lobes and within the “CC pouch” as anechoic triangulations (Lisciandro et al. 2009, 2015, 2019; Hnatusko et al. 2019).

      After interrogating the abdominal cavity, return to the starting point of the DH view. The probe is then rocked toward the patient's sternum, remaining on a strict longitudinal plane searching for the “cardiac bump,” the reverberation of the beating heart against the diaphragm (Figure 6.11). The “cardiac bump” is used to diagnose pericardial effusion and rounded effusion, and as a single view, the “racetrack sign” (see Chapters 7, 18 and 21).

      Then use the DH view as an acoustic window via the liver and gallbladder into the thorax to interrogate the pleural cavity for the presence or absence of pleural effusion, anechoic triangulated effusion, and lung along the pulmonary–diaphragmatic interface (see Chapters 7, 18, and 21).

      Pearl and Pitfall: