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Questions Asked at the HRU (SRU) Viewa
Is there any free fluid in the abdominal (peritoneal) cavity?	Yes or no
How much free fluid is at the HRU view using the AFAST AFS system?	0, 1/2 or 1
What does the small intestine look like?b	Unremarkable or abnormal
What does the spleen look like?b	Unremarkable or abnormal
Is the liver in view in the transverse plane of the umbilicus?b	Yes or noIf yes, suspect hepatomegaly
Is the stomach in view in the transverse plane of the umbilicus?b	Yes or noIf yes, gastric distension
Could I be mistaking an artifact or pitfall for pathology?	Know pitfalls and artifacts

^a Note that this view is the HRU view in right lateral recumbency and the SRU 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 final AFAST view that is used for the AFS is the hepato‐renal umbilical (HRU) view when the patient is in right lateral recumbency. The HRU view is imaged by placing the probe just ventral to the umbilicus while staying in the transverse plane of the umbilicus. Typically the HRU view includes loops of small intestine and often the spleen, especially in dogs. Its target organs are in reality the small intestine and spleen (Figures 6.30 and 6.31). At the level of the umbilicus, the liver and stomach should not be in view unless either is severely enlarged or distended, triggering additional imaging, such as radiography. The liver and right kidney are not part of the HRU view.

The probe with the marker toward the head in longitudinal (sagittal) orientation is placed just under the umbilicus and fanned through the most gravity‐dependent region referred to as the “HRU pouch” (see Figure 6.30). Find evidence that you are in fact imaging intraabdominal structures such as the spleen or small intestine. In larger dogs, it is possible to be imaging through the abdominal muscles and not within the abdominal cavity.

The probe is not routinely run under the patient unless imaging the right kidney for the HR5th bonus view (Lisciandro et al. 2009; Lisciandro 2011).

Excessive probe pressure may cause small volumes of free fluid to move away or, in other words, to either side of the probe head and be missed.

In contrast to the previous three AFAST views, rotating the probe counterclockwise for transverse imaging at the HRU view (and SRU view when in left lateral) helps differentiate small intestinal loops from free fluid by making the small intestine in transverse or cross‐section appear like “hamburgers” and in longitudinal or sagittal appear like “highways” because the small intestine consists of five ultrasonographic layers (see Figure 6.22 and Chapter 12).

When the spleen is present, use it as an acoustic window to interrogate for free fluid between its capsule and loops of small intestine.

In the first edition, this view was named the hepato‐renal (HR) view and referred to as “The Big Lie” because the liver and the right kidney are not routinely examined, so neither “HR” target organ is directly scanned (Lisciandro 2014a). So we have renamed the HR view as the “HR umbilical view” to be more descriptive of where the probe is placed, and now advocate that the small intestine and spleen be its target organs.

Figure 6.27. Calculi versus intestinal tract. The sonographer will readily appreciate deviations from the expected appearance of the urinary bladder at the CC view. In images (A), (C) and (E) bladder calculi are evident by clean shadowing through the far‐field and contained within the lumen of the urinary bladder. Moreover, they should settle at the “CC pouch” where free fluid would pocket being at the CC view's most gravity‐dependent region. In (B), (D) and (F) are examples of air‐filled intestinal tract that mimic urinary bladder calculi illustrating how care should be taken. By examining (and magnifying) more closely, the bladder lumen can be seen to be pushed into the lumen by the loop of intestinal tract as in (B) and (D) indicated by the cursors (V). Moreover, an abdominal radiograph may be added to the diagnostic work‐up.

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

Figure 6.28. Various abnormal intraluminal urinary bladder findings. (A) An irregular urinary bladder wall in its apical region suggestive of chronic cystitis. (B) A soft tissue mass in the trigone region of the urinary bladder of an older female dog that was hit by a car (blunt trauma). The condition was captured and the dog diagnosed with a transitional cell carcinoma that lived with treatment for another 11 months. Color flow Doppler could be additionally applied to evaluate for blood flow (not shown). (C) Bladder calculi in a diabetic being admitted for hospitalized care. (D) A large thrombus in an older male bluntly traumatized dog. Color flow Doppler was helpful for documenting absent flow.

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

Pitfall: Excessive probe pressure will cause small volumes of free fluid to move away to either side of the probe head and be potentially missed.

Pitfall: If the probe is not directed into the abdominal cavity or lacks adequate depth then you may be imaging through planes of body wall or “imaging through bacon,” as the author likes to say.

Pearl: The HRU view (SRU view in left lateral recumbency) is performed just ventral (right below) to the umbilicus to image the most gravity‐dependent area of the laterally recumbent dog or cat.

Pearl: Stay longitudinal (sagittal) at all sites (DH, SR, CC) except at the HRU view where it is helpful to perform both longitudinal (fanning) and transverse (rotating to the left or counterclockwise) imaging to discriminate free fluid (anechoic black triangles) from small intestine.

Figure 6.29. Pitfall of the thigh or a mass or other. In (A) and (B) are identical images unlabeled and labeled. The large circle encompasses the region of interest and its suspect origin of being the thigh muscle. The smaller circles are where typically the femoral artery and vein would be located with the patient in lateral recumbency and observing for pulsation or applying color Doppler would be helpful. The image shows how the thigh can push into the urinary bladder or stool in the colon or a caudal abdominal mass and make odd impressions when imaging the CC view with a patient in lateral recumbency. A digital rectal examination as part of a good physical examination with or without more advanced imaging is an ancillary evaluation to increase the probability of being correct. From the still B‐mode image, the exact origin of the circled structure may be unclear. UB, urinary bladder.

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

Figure 6.30. HRU view in a dog. In (A) and (B) the direction of the probe is shown externally ventral to midline at the level of the umbilicus with the objective to image and fan through the most gravity‐dependent “HRU pouch” illustrated by the white curved line. (B) A similar image with anatomy overlay that correlates with CT image in (C). The target organs for the HRU (and SRU) view are in reality the small intestine and spleen and either or both should be recognized to confirm that you are imaging the abdominal cavity. In (D), (E) and (F) the expected sonographic images are shown. 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.

Figure 6.31. Examples of typical negative studies at the HRU (SRU) view. The target organs are the small intestine and spleen. By imaging either or both, the sonographer knows they are within the abdominal cavity. (A) and (B) are the same image labeled and unlabeled, showing how the small intestine in cross‐section, transverse orientation, appears like “hamburgers” and in longitudinal or sagittal appears like “highways.” In (B) the circle highlights an area that may or may not have a small triangulation of free fluid, illustrating the difficulty in seeing small pockets of fluids (milliliters) in between intestinal loops because of the anechoic layers of intestine. A better strategy is shown in (C) by using the spleen as an acoustic window and looking for free fluid on its far side. In (D) is another region in which soft tissue is in proximity to small intestine as a better strategy to detect small‐volume effusions at this view than in (A) and (B).

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

If the right (left in left lateral recumbency) kidney needs to be imaged because of concern for retroperitoneal injury, or when hematuria exists, then the HR5th (SR5th in left lateral recumbency) bonus view should be performed. Once the four AFAST views used for the AFS are mastered, the HR5th/SR5th bonus views should be considered as an add‐on skills and incorporated for all subsequent patients.