Editorial Type: Case Reports
 | 
Online Publication Date: 01 Mar 2004

Normal and Abnormal Ultrasonographic Findings That Mimic Small Intestinal Intussusception in the Dog

DVM, PhD, Diplomate ECVDI,
DVM, PhD, MRCVS,
DVM, PhD, and
DVM, PhD
Article Category: Other
Page Range: 147 – 151
DOI: 10.5326/0400147
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On ultrasonographic examination of the abdomen, the appearance of healthy intestine, enteritis secondary to an intestinal foreign body, and postpartum involution of the uterus may be visualized in some imaging planes as a target-like structure that is subsequently misinterpreted as intestinal intussusception. To avoid misdiagnosis, the ultrasonographer should ensure multi-plane scanning of the lesion, paying particular attention to the completeness of the lesion’s peripheral ring structure and the overall width of the concentric rings of the target-like lesion. The presence of a semilunar or G-shaped hyperechoic center and the visualization of the inner intussusceptum (extending into the intussusception lumen) can be useful ultrasonographic findings that distinguish an intussusception from other lesions or from healthy tissues. These principles are illustrated through the following case presentations.

Introduction

Abdominal radiography, including survey radiographs and contrast studies, has been considered the principal noninvasive diagnostic method of intestinal intussusception in dogs and cats.1 Ultrasonography has also been used for the diagnosis of intestinal intussusception in humans and animals.2–4 The ultrasonographic pattern of intestinal intussusception may vary with the quality of the image, the length of bowel involved, the duration of the disease process, and the orientation of the imaging plane in relation to the axis of the intussusception.35 In transverse ultrasonographic images, the juxtaposition of the wall layers of the intussuscipiens and inner and outer intussusceptum creates multiple hyperechoic and hypoechoic concentric rings that surround a hyperechoic center. This is often referred to as the “multiple concentric rings sign” [Figures 1, 2]. The hyperechoic center represents mesenteric fat that is pulled into the intussusception lumen [Figure 1] or mesenteric fat and compressed inner intussusceptum [Figure 2]. In longitudinal images, multiple hyperechoic and hypoechoic parallel lines are usually observed.

The “multiple concentric rings sign” is considered specific for intestinal intussusception in animals.35–7 However, this sign may be indistinctly visible in vivo, possibly from compression of the mucosal and serosal surfaces and the presence of bowel edema in affected sections of intestine.38 In such cases, the target-like lesion is usually configured of one to three, thick or thin, concentric rings around a hyperechoic center visualized on transverse ultrasonographic images in humans and animals [Figure 3].47–9

While the “multiple concentric rings sign” is highly indicative of intestinal intussusception, other intra-abdominal conditions and anatomical structures may mimic this finding on ultrasonographic examination. These include any cause of bowel-wall thickening (e.g., inflammation, neoplasia, edema, bleeding into the intestinal wall), intestinal ascariasis, or an area of volvulus.10–16 Even nonpathogenic conditions can, depending on the ultrasonographic imaging plane, take on a target-like appearance including healthy bowel, normal lymph nodes,817 and normal involuting uterus.18 Therefore, the target configuration is typical of hollow visceral abnormalities and is nonspecific for intestinal intussusception unless multiple wall layers are recognized.5

The goals of this article are to provide case examples of normal and abnormal abdominal ultrasonographic findings that may have a target-like appearance and may be confused with intestinal intussusception, and to offer information on differentiating ultrasonographic features in order to minimize the misdiagnosis of intestinal intussusceptions.

Case Reports

Case No. 1

Abdominal radiography and ultrasonography were performed in a 4-month-old, male German shepherd dog with a clinical diagnosis of acute enteritis or gastroenteritis in order to confirm or rule out the clinical suspicion of intestinal intussusception. No mass was detected on abdominal palpation. Plain radiographs of the abdomen were unremarkable. A target-like structure composed of multiple, hyperechoic and hypoechoic, very thin, well-differentiated concentric rings around a circular hyperechoic center was detected during abdominal ultrasonography. However, an incomplete concentric rings pattern or a pseudo-target pattern rather than a true-target pattern was evident [Figure 4A]. The overall width of the rings varied between 4 mm and 6 mm, and the diameter of the center was 2 mm. By changing the probe orientation and imaging the structure in an oblique or longitudinal direction, a normal intestinal pattern was revealed [Figure 4B].

Case No. 2

A 5-year-old, male rottweiler with a clinical diagnosis of chronic enteritis was presented for abdominal ultrasonography following the detection of a mass on abdominal palpation. Plain abdominal radiographs revealed tubular viscus and a localized small intestinal dilatation. Abdominal ultrasonography revealed a target-like structure composed of hyperechoic and hypoechoic rings surrounding a curvilinear-shaped, strongly hyperechoic center that cast an acoustic shadow [Figure 5A]. The acoustic shadow prevented the visualization of the entire periphery of the lesion, resulting in an incomplete concentric ring pattern or a pseudo-target rather than a true target-like pattern. The overall width of the rings was 7 mm, and the initial ring adjacent to the hyperechoic center was hypoechoic-to-anechoic. Upon reorienting the ultrasonographic imaging plane, longitudinal scans revealed hyperechoic and hypoechoic parallel lines that were not clearly visualized because of a shadow cast by a strong echogenic line. Markedly increased peristaltic activity and mild bowel dilatation from fluid accumulation proximal to the lesion were also identified. Based predominantly on the small width of the concentric rings, the echogenic line, and the shadowing detected, a presumptive diagnosis of incomplete ileus secondary to the presence of an intestinal foreign body was made.

Exploratory celiotomy was performed immediately following the ultrasonographic examination and confirmed incomplete ileus associated with an intestinal linear foreign body, intestinal fluid accumulation, and a 6-mm thick intestinal wall at the site of obstruction. Although spontaneous reduction of an intussusception may have occurred between ultrasonography and surgery, it was excluded in this case because the intestinal wall thickness measured on ultrasonography and at exploratory celiotomy was the same. Chronic enteritis was confirmed on intestinal biopsy, with histopathology identifying infiltration of the intestinal mucosa with lymphocytes and neutrophils and thickening of the intestinal muscularis.

Attempts to interpret the ultrasonographic images were made postoperatively. The strong hyperechoic center with the acoustic shadow represented the foreign body. The initial, inner hypoechoic-to-anechoic ring likely represented fluid accumulation in the intestinal lumen, and the next five rings represented the mucosal surface, mucosa, submucosa, muscularis, and serosa of the adjacent intestinal wall [Figure 5B]. The ring representing the muscularis layer appeared to be thicker than the other rings, and this finding was compatible with the muscularis hypertrophy identified on histopathology. Such thickening likely arose from foreign-body-induced, chronic, incomplete intestinal obstruction.19

Case No. 3

A 3-year-old, female collie was presented with a history of diarrhea 5 days postpartum. A mass was detected in the caudal abdomen on palpation. Plain abdominal radiographs revealed a tubular viscus and mild loss of serosal detail at the caudal aspect of the abdominal cavity, just craniodorsal to the urinary bladder. Ultrasonographic evaluation of the abdomen revealed mild intestinal hypermotility and a 24 × 32-mm, target-like structure composed of outer mild hyperechoic, middle hypoechoic, and inner mild hyperechoic rings surrounding a small, circular, hypoechoic center. The mass was located at the craniodorsal aspect of the urinary bladder and extended caudally, dorsal to the bladder neck. The outer margin of the mass, defined by the peripheral ring, was irregular. The overall widths of the rings were measured at 12 to 14 mm. A tubular mass was detected on longitudinal images following reorientation of the ultrasonographic probe. A presumptive diagnosis of a postpartum involution of the uterus was made, primarily based on the location of the identified structure.

The small, hypoechoic center likely represented mild fluid accumulation within the uterine lumen; the inner mild hyperechoic ring likely represented the endometrium; the middle hypoechoic ring represented the myometrium; and the outer mild hyperechoic ring was likely the fat and connective tissue between the serosa and myometrium [Figure 6].18 Ultrasonographic examination of the abdomen 15 days later was unremarkable.

Discussion

Ultrasonography provides the opportunity to generate sectional images of the structures being examined. To avoid misinterpretation of images, the ultrasonographer must be familiar with normal three-dimensional anatomy to recognize artifacts and to interpret normal structural variations. Ultrasound is sensitive to alterations in the shapes of structures, and the shape of an object can be artifactually distorted if an off-axis view is obtained. Distortion may also be obtained if transducer pressure is applied to the object being imaged or when an organ with normal motility is examined.

Normal intestinal motility often results in apposition of adjacent intestinal segments and, depending upon the plane of the imaging angle, may result in the visualization of an incomplete multiple concentric rings structure as demonstrated in case no. 1. Such cases may be misinterpreted as intussusceptions if the incompleteness of the peripheral rings is overlooked [Figure 4A]. Therefore, a multiplane imaging technique of the suspected intussusception is extremely critical to avoid a misdiagnosis. Incompleteness of the periphery of the rings has also been used as a differentiating feature of the intestinal intussusception from other pathogenic conditions of the intestine. In one prior report, a multilayered appearance of the duodenal walls (in close apposition from plication of the duodenum around a linear piece of cloth) initially mimicked intussusception, and the misdiagnosis was prevented with recognition of the incomplete nature of the rings’ periphery.20 The rings’ peripheral incompleteness in case no. 2 was essential in excluding the diagnosis of intussusception.

The intestinal wall normally ranges between 2 to 3 mm in thickness on ultrasonographic examination. Therefore, the overall width of the concentric rings of an intussusception, created by the juxtaposition of the walls of the inner and outer intussusceptum and the wall of the intussuscipiens, should equate to 6 to 9 mm at the most; however, edema formation may result in an increase in the width of the rings to >9 mm.

When searching for an intussusception in people, the characteristic ultrasonographic finding is an easily detectable mass that is 30 to 50 mm in diameter.10 Additional supportive findings of small intestinal intussusception include ultrasonographic demonstration of a 20- to 30-mm, short, donut-like or target-like lesion, especially in the left abdomen or paraumbilical regions in pediatric patients.2122 To the authors’ knowledge, there are no reports detailing the overall diameter of the target-like mass or the width of the concentric rings of the intussuscepted bowel in animals; however, the authors suggest that the diameter of the target-like mass as well as the overall width of the concentric rings could be essential ultrasonographic features in dogs. In the authors’ experience, a target-like mass composed of concentric ring(s) with an overall width of <8 to 9 mm, is unlikely to be an intestinal intussusception. In case nos. 1 and 2, the small overall width of the rings was an essential finding in ruling out intestinal intussusceptions, but this finding was not helpful in case no. 3. The diameter of the target-like mass or the width of the concentric rings of the intussuscepted bowel in animals should be investigated further.

The presence of eccentric, semilunar, or G-shaped echogenic mesenteric fat and the recognition of the inner intussusceptum at the center of the target-like mass on transverse ultrasonographic images are considered useful features when differentiating intestinal intussusception from other entities.410 The absence of these features in case nos. 2 and 3 was helpful but not essential to prevent a misdiagnosis of intussusception, because their absence, which is a variable finding, does not definitively rule out the presence of an intussusception.4

The importance of performing orthogonal ultrasonographic imaging of the detected target-like lesion cannot be overstated, since the finding of “multiple hyperechoic and hypoechoic parallel lines” is considered a characteristic ultrasonographic pattern of intestinal intussusception in longitudinal images in dogs.4 However, this pattern alone is not specific for intestinal intussusception unless the characteristic “trident configuration” formed by the wall of the intussuscipiens and inner and outer intussusceptum is apparent.34

As mentioned earlier, the exact topography of the detected lesion may help in the diagnosis of intestinal intussusception in people.2122 The location of the target-like structure was essential in identifying it as a normal, involuting uterus in case no. 3; however, lesion location was not helpful in case nos. 1 and 2. Unfortunately, establishing the exact topography of an intussusception during ultrasonography is not possible because of the mobility of the bowel mass and the influence of stomach and bladder size.

Intussusception is always associated with obstruction of the intestinal lumen. Early or incomplete obstruction may cause increased peristalsis when compared to normal bowel, or it may produce an adynamic bowel if associated with ileus. Abnormal intestinal motility can be observed with other abdominal conditions and usually is not considered a characteristic ultrasonographic finding in cases of intussusception.

Conclusion

The cases reported in this study clearly demonstrate that both healthy bowel and other intra-abdominal conditions (e.g., enteritis due to intestinal foreign body, postpartum involution of the uterus) may appear as target-like structures that have the potential of being misdiagnosed as intestinal intussusceptions, especially by a novice ultrasonographer. To avoid ultrasonographic misdiagnosis in these clinical settings, the authors recommend multiplane scanning of the lesion to better visualize the completeness of the rings’ periphery and measurement of the overall width of the concentric rings. Ultrasonographic demonstration of a target-like mass in the midabdomen with complete periphery of rings and an overall width of >8 to 9 mm of the concentric rings appear to support the diagnosis of intestinal intussusception. The presence of a semilunar or G-shaped hyperechoic center and the visualization of the inner intussusceptum in the intussusception lumen can also be useful ultrasonographic findings.

Figure 1—. “Multiple concentric rings sign” in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. A hyperechoic center representing mesentery (m) in the lumen, and part of the small intestine (i) representing the inner intussusceptum are surrounded by multiple hyperechoic and hypoechoic concentric rings. Small anechoic foci in the mesentery represent either vessels or dilated lymphatics. The overall width of the rings measured 10 mm.Figure 1—. “Multiple concentric rings sign” in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. A hyperechoic center representing mesentery (m) in the lumen, and part of the small intestine (i) representing the inner intussusceptum are surrounded by multiple hyperechoic and hypoechoic concentric rings. Small anechoic foci in the mesentery represent either vessels or dilated lymphatics. The overall width of the rings measured 10 mm.Figure 1—. “Multiple concentric rings sign” in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. A hyperechoic center representing mesentery (m) in the lumen, and part of the small intestine (i) representing the inner intussusceptum are surrounded by multiple hyperechoic and hypoechoic concentric rings. Small anechoic foci in the mesentery represent either vessels or dilated lymphatics. The overall width of the rings measured 10 mm.
Figure 1 — “Multiple concentric rings sign” in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. A hyperechoic center representing mesentery (m) in the lumen, and part of the small intestine (i) representing the inner intussusceptum are surrounded by multiple hyperechoic and hypoechoic concentric rings. Small anechoic foci in the mesentery represent either vessels or dilated lymphatics. The overall width of the rings measured 10 mm.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400147

Figure 2—. Multiple, thin, hyperechoic and hypoechoic concentric rings (i.e., “multiple concentric rings sign”) surround a hyperechoic center in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. The overall width of the rings measured 10 mm.Figure 2—. Multiple, thin, hyperechoic and hypoechoic concentric rings (i.e., “multiple concentric rings sign”) surround a hyperechoic center in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. The overall width of the rings measured 10 mm.Figure 2—. Multiple, thin, hyperechoic and hypoechoic concentric rings (i.e., “multiple concentric rings sign”) surround a hyperechoic center in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. The overall width of the rings measured 10 mm.
Figure 2 — Multiple, thin, hyperechoic and hypoechoic concentric rings (i.e., “multiple concentric rings sign”) surround a hyperechoic center in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. The overall width of the rings measured 10 mm.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400147

Figure 3—. Transverse ultrasonographic image of an ileocolic intussusception in a dog. A target-like mass (arrows are denoting the mass borders) is composed of a thick, isoechoic ring around a mixed echogenicity center. The width of the ring measured 11 mm.Figure 3—. Transverse ultrasonographic image of an ileocolic intussusception in a dog. A target-like mass (arrows are denoting the mass borders) is composed of a thick, isoechoic ring around a mixed echogenicity center. The width of the ring measured 11 mm.Figure 3—. Transverse ultrasonographic image of an ileocolic intussusception in a dog. A target-like mass (arrows are denoting the mass borders) is composed of a thick, isoechoic ring around a mixed echogenicity center. The width of the ring measured 11 mm.
Figure 3 — Transverse ultrasonographic image of an ileocolic intussusception in a dog. A target-like mass (arrows are denoting the mass borders) is composed of a thick, isoechoic ring around a mixed echogenicity center. The width of the ring measured 11 mm.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400147

Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).
Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).Figures 4A, 4B—. (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).
Figures 4A, 4B — (A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400147

Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.
Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.Figures 5A, 5B—. (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.
Figures 5A, 5B — (A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400147

Figure 6—. Transverse ultrasonographic image of a female dog (case no. 3) 5 days postpartum. The involuting uterus appears as a target-like structure (arrows) composed of an outer mild hyperechoic (i.e., fat and connective tissue between the serosa and myometrium), middle hypoechoic (i.e., myometrium), and inner mild hyperechoic (i.e., endometrium) concentric rings around a small, hypoechoic center (i.e., fluid within the uterine lumen). Note the irregular peripheral rings margin (c=center).Figure 6—. Transverse ultrasonographic image of a female dog (case no. 3) 5 days postpartum. The involuting uterus appears as a target-like structure (arrows) composed of an outer mild hyperechoic (i.e., fat and connective tissue between the serosa and myometrium), middle hypoechoic (i.e., myometrium), and inner mild hyperechoic (i.e., endometrium) concentric rings around a small, hypoechoic center (i.e., fluid within the uterine lumen). Note the irregular peripheral rings margin (c=center).Figure 6—. Transverse ultrasonographic image of a female dog (case no. 3) 5 days postpartum. The involuting uterus appears as a target-like structure (arrows) composed of an outer mild hyperechoic (i.e., fat and connective tissue between the serosa and myometrium), middle hypoechoic (i.e., myometrium), and inner mild hyperechoic (i.e., endometrium) concentric rings around a small, hypoechoic center (i.e., fluid within the uterine lumen). Note the irregular peripheral rings margin (c=center).
Figure 6 — Transverse ultrasonographic image of a female dog (case no. 3) 5 days postpartum. The involuting uterus appears as a target-like structure (arrows) composed of an outer mild hyperechoic (i.e., fat and connective tissue between the serosa and myometrium), middle hypoechoic (i.e., myometrium), and inner mild hyperechoic (i.e., endometrium) concentric rings around a small, hypoechoic center (i.e., fluid within the uterine lumen). Note the irregular peripheral rings margin (c=center).

Citation: Journal of the American Animal Hospital Association 40, 2; 10.5326/0400147

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Copyright: Copyright 2004 by The American Animal Hospital Association 2004
<bold> <italic toggle="yes">Figure 1</italic> </bold> —
Figure 1 —

“Multiple concentric rings sign” in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. A hyperechoic center representing mesentery (m) in the lumen, and part of the small intestine (i) representing the inner intussusceptum are surrounded by multiple hyperechoic and hypoechoic concentric rings. Small anechoic foci in the mesentery represent either vessels or dilated lymphatics. The overall width of the rings measured 10 mm.

<bold> <italic toggle="yes">Figure 2</italic> </bold> —
Figure 2 —

Multiple, thin, hyperechoic and hypoechoic concentric rings (i.e., “multiple concentric rings sign”) surround a hyperechoic center in a transverse ultrasonographic image of an ileocolic intussusception in a dog. Arrows denote the intussusception’s border or peripheral ring. The overall width of the rings measured 10 mm.

<bold> <italic toggle="yes">Figure 3</italic> </bold> —
Figure 3 —

Transverse ultrasonographic image of an ileocolic intussusception in a dog. A target-like mass (arrows are denoting the mass borders) is composed of a thick, isoechoic ring around a mixed echogenicity center. The width of the ring measured 11 mm.

<bold> <italic toggle="yes">Figures 4A, 4B</italic> </bold> —
Figures 4A, 4B —

(A) Multiple hyperechoic and hypoechoic concentric rings around a hyperechoic center in a dog with suspected intussusception (case no. 1). The overall width of the rings measured 4 to 6 mm. Note the incompleteness of the rings at the 9 o’clock position of the target. (B) By changing the probe orientation, the target-like lesion was defined as healthy intestine. The hyperechoic and hypoechoic rings represented the normal opposing layers of the intestinal wall. The increased overall width of the rings in certain regions was due to juxtaposition of the walls of two adjacent segments of the small intestine (arrows) (m=mesentery).

<bold> <italic toggle="yes">Figures 5A, 5B</italic> </bold> —
Figures 5A, 5B —

(A) Transverse ultrasonographic image of the small intestine of a dog with chronic enteritis (case no. 2). Note the hyperechoic and hypoechoic concentric rings surrounding a curvilinear hyperechoic center. An acoustic shadow is evident below the echogenic center. A linear intestinal foreign body and thickening of the intestinal wall were revealed at exploratory celiotomy. (B) Magnification of the image in Figure 5A. The intestinal wall is mildly compressed at the top of the target contour from the pressure of the transducer. 1=fluid in the lumen; 2=hyperechoic mucosal surface; 3=hypoechoic mucosa; 4=hyperechoic submucosa; 5=hypoechoic muscularis; 6=hyperechoic serosa; FB=foreign body. The ring representing the muscularis layer (5) appears to be thicker than the other rings.

<bold> <italic toggle="yes">Figure 6</italic> </bold> —
Figure 6 —

Transverse ultrasonographic image of a female dog (case no. 3) 5 days postpartum. The involuting uterus appears as a target-like structure (arrows) composed of an outer mild hyperechoic (i.e., fat and connective tissue between the serosa and myometrium), middle hypoechoic (i.e., myometrium), and inner mild hyperechoic (i.e., endometrium) concentric rings around a small, hypoechoic center (i.e., fluid within the uterine lumen). Note the irregular peripheral rings margin (c=center).

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