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Questions Asked at the SR (HR) Viewa
Is there any free fluid in the abdominal (peritoneal) cavity?	Yes or no
How much free fluid is at the SR view using the AFAST AFS system?	0, 1/2, 1
What does the left (right when in left lateral) kidney look like?b	Unremarkable or abnormal
What does the spleen (liver when in left lateral) look like?b	Unremarkable or abnormal
Could I be misinterpreting an artifact or pitfall as pathology?	Know pitfalls and artifacts

^a Note that this view is the SR view in right lateral recumbency and the HR view in left lateral recumbency.

^b It is important to know that the AFAST target‐organ approach for parenchymal abnormalities is binary as “unremarkable” or “abnormal” to capture the case for additional imaging and confirmatory testing. More interpretative skills may be gained through experience, and additional ultrasound study and training.

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

The SR view includes visualization of both the spleen (peritoneal cavity) and the left kidney (retroperitoneal space) (Figures 6.17 and 6.18).

Figure 6.17. The SR view in a dog. In (A) is the external location where the ribs meet the hypaxial muscles dorsally, followed by (B) through (F) showing the relevant anatomy that includes the left kidney, the head of the spleen where it attaches to the greater curvature of the stomach, and the viscus often air‐filled stomach cranially and colon caudally. Ultrasound cannot image past air and thus each organ causes dirty shadowing. The left kidney is retroperitoneal and the spleen is peritoneal. LK, left kidney; SI, small intestine; Sp, spleen; ST, stomach. 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 SR target organs are readily imaged in the preferred positioning of right lateral recumbency by placing the probe just caudal to the last rib and dorsally where the rib and the hypaxial muscles meet. The probe is fanned in both directions in longitudinal (sagittal) orientation, recalling that the left kidney is protected by the hypaxial muscles, and in close proximity to the great vessels because of the short renal artery and vein to the aorta and CVC, respectively.

If the left kidney is not located, the probe is rocked cranially under the costal arch and then again fanned since in most dogs the left kidney would tend to be located more cranial than caudal to your starting point.

Once the left kidney is located, it is interrogated by making it as longitudinally symmetrical as possible, and then fanning through it longitudinally (sagittal) in both directions for any free fluid and any obvious renal and perirenal pathology.

The probe is then rocked cranially to search for the head of the spleen, recalling that in dogs and cats, the spleen is reliably found because it is attached by its short gastric vessels to the greater curvature of the stomach in this region.

Figure 6.18. Examples of typical negative studies at the SR view. In (A) the air‐filled stomach (ST) and the colon shadow through the far‐field, giving the SR view its characteristic pie‐piece of information with the head of the spleen (Sp) abutting the left kidney. In (B) the wall of the stomach is outlined (V) and a large swath of the head of the spleen is fanned and interrogated while remaining at the SR view's external location. Do not wander from this region to look for the spleen (see Focused Spleen below). In (C) is another example of the target organs of the head of the spleen and the left kidney being in view. In (D) interposing small intestine is past the spleen to the far‐field (“hamburger” look of small intestine) without the left kidney target organ. (E) shows the left kidney without the spleen target organ, which will require rocking the probe cranially. In (F) are the left kidney and adjacent great vessels, keeping in mind the retroperitoneal anatomy includes the CVC, the aorta, renal artery and vein, and adrenal glands. Note the consistency in the images with their proportionality and location of the relevant SR view structures of the left kidney, spleen, stomach, and colon.

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

When free fluid is present, it is most commonly seen between the spleen and cranial left kidney, or between the cranial pole of the left kidney and the wall of the colon (Figure 6.19).

In dogs, the spleen may be used to locate the left kidney by following it caudally and medially because of its anatomical association with the left kidney, or by fanning along the great vessels since the left kidney is closely attached via its relatively short renal artery and vein. If you are having problems finding the left kidney, you have a few options.

 The spleen in dogs and cats may be used to locate the left kidney by following the spleen caudally and medially to bring you to the left kidney.

 Fan along the great vessels, paying attention to the probe's direction, recalling that the left kidney (and right) are closely attached via their respective renal artery and vein.

 Making sure that you have not drifted too far ventrally from the angle of the costal arch and hypaxial junction and into the abdomen.

 You are pushing (compression) too hard into the patient and in fact pushing the left kidney (and right) out of view.

Pearl: In most cats and many small dogs, both the left and right kidneys can be viewed through the single SR (or HR) view with increased depth (Figures 6.20 and 6.21).

Fanning dorsally screens for any pathology associated with the great vessels (aorta and caudal vena cava) and adrenal glands. The great vessels are common confounders and cause false positives, which are easily overcome by remembering that free fluid is rarely a linear anechoic (black) stripe(s) but rather anechoic triangulations, and thus linear anechoic stripes are more likely to be blood vessels and intestinal tract (see Figures 6.18 and 6.20). The only major exception is anechoic stripe(s) at the DH view between the liver and diaphragm (Lisciandro et al. 2015, 2019; Romero et al. 2015).

The great vessels are identified in B‐mode by their shape, being linear in longitudinal and circular in transverse orientation with pulsation. Color flow Doppler may also be used to detect flow. Turning your probe transversely (turn left or counterclockwise) should change the vessel's appearance from a linear anechoic (black) rectangular shape to an anechoic (black) circle.

Retroperitoneal fluid raises the suspicion for hemorrhage, urine, and sterile and septic effusions placed into clinical context, and when found and safely accessible, fluid sampling should take place, and when inaccessible or too risky to sample, more advanced imaging is likely indicated.

 Cranial to the kidneys, origin of retroperitoneal fluid would generally include the kidneys, vertebral bodies, the great vessels and adrenal glands.

 Caudal to the kidneys, origin of retroperitoneal fluid would generally include the kidneys, ureters, vertebral bodies, and pelvis (see Figure 6.19, see also Chapters 10 and 11).

Retroperitoneal versus intraabdominal (peritoneal) fluid can be further assessed by changing patient position by moving them to a standing position and seeing if the free fluid remains in the least gravity‐dependent SR view (retroperitoneal more likely), and noting that the least gravity‐dependent SR view is rarely the only positive AFAST view in right lateral recumbency.

Pearl: Retroperitoneal fluid is not part of the AFS. Its size should be noted by its largest dimension (length, width, height) measured by either the “eyeball method” (using the centimeter scale on the ultrasound screen), or more precisely using your machine's caliper function.