Point-of-Care Ultrasound Techniques for the Small Animal Practitioner. Группа авторов
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Use of the DH View and Vet BLUE for Deep Lung Lesions
See Chapters 22 and 23 for more detail. However, it is important to appreciate that the DH view serves as a deep window into lung pathology along its diaphragmatic interface (see Figures 6.14 and 23.21).
AFAST Cysto‐Colic View Formula for Urinary Bladder Volume Estimation
The use of the CC view formula of length × height × width (cm) × 0.625 = estimation of urinary bladder volume (mL) (Lisciandro and Fosgate 2017) serves as a rapid noninvasive way in which to estimate urinary bladder volume and, with serial measurements over time, provides a noninvasive means to estimate urine production. Moreover, walking dogs and allowing them to void, then confirming an empty urinary bladder with AFAST, is another way to effectively measure urine output in the hospitalized setting.
Make your best oval in longitudinal orientation of the bladder and acquire length and height in centimeters (cm).
Rotate the probe into transverse orientation and make your best largest oval and measure width (cm) (Figure 7.15).
Calculate urinary bladder volume using length × height × width (cm) × 0.625 = estimation of urinary bladder volume (mL) (see Figure 7.15).
Urine output is estimated using change in urinary bladder volume/time.
AFAST and Its Target Organ Approach
AFAST was never meant to be a “flash exam” of the abdomen. The “flash” mentality is a quick ultrasound sweep answering a single binary question of whether fluid is present or absent, a positive or negative test. It is often used as a desultory sweep for a midabdominal mass, but without standardization of views and knowledge of anatomy at specific acoustic windows as in AFAST. Without direction, it becomes easy for the sonographer to get lost. Easily detected soft tissue conditions are often missed by abdominal radiography (Table 7.9) and the reader is referred to Chapters 8–12. The objective is through repetition and standardization to be able to tell normal from abnormal (differentiate expected from unexpected) and capture conditions that would otherwise be missed without any imaging or with radiography. As you read through Table 7.9, think about the conditions listed and how often they are missed on plain radiography. Interestingly, incidental findings during FAST exams have been reported in people (Sgourakis et al. 2012).
Figure 7.15. Measurements at the AFAST CC view for estimating urinary bladder volume. In (A) the best largest oval in the longitudinal plane is used for length (L, cm) and height (H, cm) measured as 5.01 cm and 3.22 cm, respectively. In (B) the best largest oval in the transverse plane is used for width (W, cm) measured as 4.49 cm. With these measurements the equation would be 5.01 × 3.22 × 4.49 cm × 0.625 = 45.3 mL. The volume can be compared to that aspirated when patients are catheterized immediately thereafter to gain confidence in its use (Lisciandro and Fosgate 2017).
Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX.
Table 7.9. AFAST and its target organ approach as a soft tissue screening test.
Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX.
| View | Target organ | Findings |
|---|---|---|
| DH | Gallbladder | SludgeMucoceleCalculiMasses |
| Liver | MassesObvious mottled echogenicity | |
| Caudal vena cava | Caudal caval size abnormalitiesCaval syndromeHepatic venous congestion | |
| Lung | Alveolar‐interstitial edema (B‐lines)ConsolidationMasses | |
| Heart | Pericardial effusionLeft atrial enlargement | |
| Thorax | Pleural effusionMasses | |
| SR, HR, SR5th, HR5th | KidneyLiver | PyelectasiaHydronephrosisCortical cyst(s)Perinephric cyst(s)Polycystic diseaseMassesSee DH view |
| CC | Urinary bladder | SedimentCalculiBladder wall irregularitiesMasses |
| HRU, SRU | Spleen | MassesObvious mottled echogenicityMidabdominal masses |
See respective POCUS abdomen‐related chapters for examples.
Recording AFAST Findings on Goal‐directed Templates
The use of standardized templates is imperative not only for communication of AFAST findings between veterinarians but also for the attending clinician evaluating serial findings (Figure 7.16). Goal‐directed templates also clearly define objectives, which is especially important in teaching hospitals and referral hospitals with multiple disciplines of practice including emergency and critical care, cardiology, and radiology. Being goal driven, these standardized templates also accelerate the learning curve and discipline the sonographer by making them look at certain aspects of the target organs (into the thorax for pleural and pericardial effusion [DH view]; looking at the hepatic veins for venous congestion [DH view]). The “Comments” allows for any findings outside the goal‐driven standard format to be listed, for example suspect a urinary bladder stone or mass, suspect a splenic mass, etc. Finally, the AFAST protocol and its strengths and weaknesses may be evaluated and improved upon with recorded data. Suggested templates for medical records are shown in Chapter 45 and Appendix I.
Pearls and Pitfalls, The Final Say
AFAST is superior in detecting hemorrhage to laboratory values (packed cell volume, lactate), physical examination findings, and radiography (Lisciandro et al. 2009; Rozycki 1998; Rozycki et al. 1998, 2001; McMurray et al. 2016). AFAST is an advantageous