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Stomach, small and large intestines

image of Stomach, small and large intestines
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Abstract

Abdominal ultrasonography has become in many instances a part of the minimum database in conjunction with abdominal radiography for the assessment of intestinal disease. Some of the most common indications for gastrointestinal ultrasonography include: persistent or chronic vomiting; diarrhoea; abdominal pain; palpable abdominal mass; palpable thickening of the small intestinal loops; weight loss and anorexia; suspected ingestion of foreign bodies; staging of neoplasia; suspected hernias. This chapter explains the value of ultrasonography compared with radiography and computed tomography. The chapter covers the stomach, duodenum, jejunum and large intestine. This chapter contains 12 video clips.

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Figures

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11.2 Transducer arrays and clipping area for abdominal ultrasonography. From top to bottom: multi-frequency linear; convex; and microconvex transducers.
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11.3 Short-axis view of a normal empty stomach of a cat showing the ‘wagon wheel’ appearance.
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11.4 Long-axis view of the normal canine and feline pylorus.
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11.5 Gastric functional ileus in a dog. The stomach is severely dilated and fluid-filled (F) and does not show peristaltic activity.
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11.7 Severe gastritis in a dog with chronic vomiting. The wall (between the callipers) shows generalized thickening with loss of wall layering in both long and short-axis views.
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11.9 Gastric lymphoma in a cat. Note the focal thickened and hypoechoic wall with loss of wall layering (between the callipers).
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11.10 Focal leiomyoma (+–+) in a dog with hypoglycaemia.
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11.12 Normal anatomical location of the proximal duodenum viewed from a right dorsal acoustic window. Dorsal is towards the left of the image and the duodenum (D) is ventral to the short-axis of the right kidney (RK).
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11.13 Duodenum in a dog showing normal wall layering. m = mucosa; mus = muscularis; s = serosa; sub = submucosa.
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11.15 Intestinal lymphangiectasia in a Yorkshire Terrier. Long-axis ultrasonogram of the proximal duodenum and the corresponding endoscopic view. There are hyperechoic striations in the mucosa, which are arranged parallel to one another and perpendicular to the long axis. The endoscopic image shows multifocal pinpoint white raised structures representing the dilated lacteals.
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11.16 Hyperechoic mucosal speckling in a normal dog. Small pinpoint hyperechoic foci are present throughout the mucosa and can be seen as a normal variation.
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11.17 Duodenal polyp in a cat with hyperbilirubinaemia. Ultrasonogram showing the long-axis of the polyp (+–+), which is well marginated, ovoid and homogeneously hyperechoic. Ultrasonogram showing dilatation and likely partial obstruction of the common bile duct (+–+).
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11.18 Functional ileus in a dog due to haemorrhagic gastroenteritis. Note the normal wall layering and mild distension of the jejunal segments, which are fluid-filled. A uniform population of mildly distended small intestines is common with functional ileus.
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11.19 T-shirt foreign body in a jejunal segment in a dog. There is a smooth hyperechoic structure with clean distal shadowing (arrowed) within the lumen of one jejunal segment. The fluid distending the lumen proximal to it is echogenic (between thicker arrows).
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11.20 Intestinal lymphoma in a dog. Focal hypoechoic thickening of the wall is present with a loss of wall layering (arrowed). There is also regional lymphadenopathy due to the lymphoma. The jejunal lymph nodes (arrowed) are severely enlarged, rounded, hypoechoic and display a heterogeneous echotexture.
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11.21 Histoplasmosis in a dog. There is focal jejunal wall thickening with loss of wall layering (between the callipers). The wall appears hypoechoic in the affected region. Histopathology confirmed the presence of histoplasmosis. Differential diagnoses include lymphoma, mast cell tumour, foreign body granuloma and other types of fungal and neoplastic disease.
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11.22 Intestinal intussusception in a puppy. Concentrically layered intestinal walls are evident in this cross-section of a jejunal intussusception.
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11.23 Corrugated jejunum in a dog with peritonitis. The jejunal segment has an undulating course that is fairly regular. Note the lack of plication associated with linear foreign bodies.
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11.24 Muscularis thickening in a cat with lymphoma. The muscular layer is markedly thickened in all jejunal segments. When diffuse, the main differential diagnosis is inflammatory bowel disease. Intestinal biopsy is required to differentiate neoplasia from inflammation.
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11.25 Inflammatory bowel disease in a dog. Mild generalized thickening of the mucosa is present with mild luminal distension. The mucosa has an increased echogenicity (arrowed) but the wall layering is preserved. Intestinal biopsy is necessary to rule out neoplasia.
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11.26 Reactive lymph nodes associated with chronic inflammatory bowel disease (between the callipers). The lymph nodes are increased in size and somewhat irregular in shape. The echogenicity is close to normal, being moderately echogenic, but with a heterogeneous architecture.
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11.27 Peri-intestinal focal free fluid and hyperechoic mesentery associated with an intestinal perforation due to a long-standing linear foreign body. Free peritoneal air. There is a hazy hyperechoic reverberation artefact (arrowed) at the non-dependent margin of the peritoneum. This represents free air following an intestinal perforation. Care is required not to confuse with gas-filled bowel loops adjacent to the non-dependent aspect of the abdomen. If in doubt, radiographs should be performed to assess for free air. FF = free fluid.
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11.28 Normal colon. The colon wall (arrowed) is thin with alternating hyperechoic and hypoechoic layers that are equal in diameter. Only the near wall is visible when the colon is filled with gas or faeces. Note the jejunal segment (between the callipers) adjacent to the colon whose thick mucosa helps to differentiate the two types of bowel. Normal fluid-filled colon. Due to the lack of solid faeces, both the near and far wall can be identified (arrowed).
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11.29 Ileum showing the ileocaecocolic junction in a cat with inflammatory bowel disease. The short ileum enters the colon (arrowed). The muscular layer is thickened. A plasmacytic–lymphocytic–eosinophilic inflammatory infiltration was present.
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11.30 Mildly, diffusely thickened colon wall in a cat with chronic, severe colitis diagnosed by mucosal biopsy. The wall layering is less distinct than normal, the wall thickness is 3.5 mm (normal is 1 mm) and it appears hyperechoic. The lumen is fluid-filled. Fluid-filled colon. The bladder is a good landmark for confirming that a fluid-filled bowel segment is colonic by its dorsal location to the bladder.
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11.31 Focal, circumferential infiltration of the descending colon wall in a cat. The thickened portion has a heterogeneous, hypoechoic appearance with loss of wall layering. Biopsy confirmed a carcinoma.

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Functional ileus.

This clip shows functional ileus in a dog with haemorrhagic gastroenteritis. The normal canine ileocaecal junction is seen in the first part of the clip, followed by the stomach and small intestines. The ileocaecal junction appears as a wagon wheel in cross-section and can be found by tracing the colon to the ascending portion and caecum, or by identifying the ileum on the right side of the abdomen medial to the duodenum. In this dog the small intestines are mild to moderately dilated with anechoic fluid in the lumen and show no sign of peristalsis. Any cause of functional ileus will cause this ultrasonographic appearance.

Gastric oedema.

Gastric wall oedema in a dog with chronic vomiting and diarrhoea. The gastric wall is diffusely hyperechoic and mildly thickened. The wall layering is not distinct. Differential diagnoses for this finding include gastric wall oedema, gastritis and neoplasia. Biopsy samples confirmed the presence of gastric wall oedema.

Gastric lymphoma.

The stomach of this dog has a focal wall mass that is poorly delineated, somewhat rounded and diffusely hypoechoic. There is a loss of wall layering associated with the mass, which was located in the gastric body.

Pseudolayering.

Gastric carcinoma showing pseudolayering in a dog. The stomach of this dog is shown in cross-section at the level of the body and antrum. The stomach wall is thickened and hypoechoic. A number of thick layers, alternating from hypoechoic to hyperechoic, represent pseudolayering, which is commonly seen with neoplasia, especially carcinoma.

Normal duodenal contractions.

Normal postprandial contractions of the canine duodenum. When the stomach is full and emptying in a normal manner, antegrade movement of the ingesta can be seen as it enters the duodenum. The ingesta is propulsed aborally with regular contractions of the duodenum.

Normal feline pylorus.

The pylorus is easier to identify in cats than in dogs. By following the gastric antrum to the right, the pylorus and duodenum are located in the midline of the abdomen and close to the hilus of the liver and portal vein. A mid-sagittal probe position can be used to identify the feline pylorus; whereas, in the dog, a right lateral position of the probe is necessary. Power Doppler was used to identify the position of the portal vein. Ingesta can be seen moving from the stomach into the duodenum as a rapidly moving bolus.

Normal duodenal papilla.

This clip shows the normal duodenal papilla and common bile duct in a dog. The papilla and entrance to the normal bile duct are visible. The papilla is located close to the cranial curvature of the duodenum and can be difficult to identify in deep-chested dogs. The papilla in dogs appears as a slit-like opening in the duodenal wall; whereas, in cats it has the appearance of a small nodule where the bile duct enters. The common bile duct appears thin-walled with a narrow anechoic lumen.

Inflammatory polyp.

This clip shows an inflammatory polyp at the duodenal papilla in a dog with icterus. The proximal duodenum contains anechoic fluid. The common bile duct can be seen as a mildly dilated tubular structure with anechoic contents, adjacent to the papilla and duodenum. The papilla is markedly enlarged and diffusely hyperechoic, and has caused obstruction of the bile duct. An inflammatory polypoid growth was diagnosed.

Jejunal foreign body.

This clip shows a jejunal foreign body in a dog presented with vomiting of 3 days duration. A dilated jejunal segment is visible to the left of the screen and can be traced to an intraluminal, irregularly shaped, hyperechoic structure with shadowing. The foreign body was a fruit pit.

Jejunal lymphoma.

Lymphoma of the jejunum associated with stenosis and foreign body obstruction in a cat. Focal and severe thickening of a jejunal segment is shown, with loss of wall layering and diffuse hypoechogenicity. Proximal to the wall infiltration the jejunum is dilated, and multiple, irregularly shaped structures are present in the lumen with clean acoustic shadowing. A number of empty jejunal segments can be identified adjacent to the affected segment.

Hypereosinophilic syndrome.

This clip shows hypereosinophilic syndrome in a cat with chronic vomiting. The small intestines have a generalized thickened and hypoechoic muscularis layer, which is 2--3 times thicker than the mucosa. The intestines are mildly dilated. Histopathology showed severe eosinophilic infiltration of the jejunal wall, most prominently in the muscular layer. Differential diagnoses for this finding should include lymphoma.

Colonic carcinoma.

Carcinoma of the colon in a dog with constipation and straining to defecate. The colon proximal to the mass is distended and filled with gas. As the gas-filled colon is traced distally, a focal and severe wall thickening with loss of wall layering is seen, resulting in stenosis. Histopathology confirmed the diagnosis of a carcinoma.

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