Diagnostic ultrasound in cats

Medicina pediátrica en pequeños animales

Presentation brochure

Diagnostic

ultrasound

in cats

Diagnostic ultrasound in cats

Rosa Novellas Torroja Elisabet Domínguez Miño Yvonne Espada Gerlach Yolanda Martínez Pereira Mauricio Tobón Restrepo

Diagnostic ultrasound in cats

Diagnostic

ultrasound

in cats

Diagnostic ultrasound in cats

Rosa Novellas Torroja Elisabet Domínguez Miño Yvonne Espada Gerlach Yolanda Martínez Pereira Mauricio Tobón Restrepo

Authors: Rosa Novellas Torroja, Elisabet Domínguez Miño,

Yvonne Espada Gerlach, Yolanda Martínez Pereira, Mauricio Tobón Restrepo.

Format: 22 x 28 cm.

Number of pages: 256.

Number of images: 500.

Binding: hardcover.

eBook included

RETAIL PRICE

90 €

This book provides a new insight on feline ultrasound in the daily practice. From cranial to caudal, the feline species has been thoroughly scanned, detailing for each body region the scanning technique, as well as the ultrasonography of both the normal and the diseased organ.

In each chapter, key points highlight the special features of feline species, and help the reader to focus on the most important. A number of short ultrasound clips along with an additional chapter on Ultrasound guided sampling are also available in the electronic version of the book, increasing even more the interest of this book.

An up-to-date text and a number of references to the latest studies on feline ultrasound make of this book a valuable tool for those veterinary surgeons wanting an in-depth knowledge of diagnostic ultrasound in cats.

Diagnostic ultrasound in cats

Presentation of the book Diagnostic ultrasonography has become during the last years a widely available and routinely used diagnostic imaging technique in veterinary medicine. As a matter of fact, the value of ultrasound in the day-to-day approach to small animal diseases is well-known.

Several books on small animal ultrasound are available in the veterinary literature, although all of them are dedicated to both canine and feline patients and many are mainly focused on canine. However, during the last decades, the popularity of cats as domestic pets has increased to the point that, in some countries, cats have already outnumbered dogs as the most popular pet.

It is therefore mandatory for veterinary surgeons to increase their knowledge of the most common diseases of this species to offer the better service possible to their patients and clients.

As it is usually said “cats are not little dogs�: anatomical particularities of the species, and the differences in the occurrence and the appearance of some diseases warrant the existence of a book dedicated to feline ultrasound.

Rosa Novellas Coordinator

The authors Rosa Novellas Torroja Graduated in 2003 at the Universitat Autónoma de Barcelona. After graduating she developed her PhD project in diagnostic imaging and in 2007 obtained the PhD at the same university. In 2007, she enrolled a residency training programme in veterinary diagnostic imaging at the Royal (Dick) School of Veterinary Studies in Edinburgh. In 2008 she moved to Glasgow were she continued and finished the residency at Glasgow University Vet School.

In 2010 she became a diplomate of the European College of Veterinary Diagnostic Imaging (ECVDI). She is currently working as an associate lecturer at the Universitat Autónoma de Barcelona and a member of the diagnostic imaging service of the Fundació Hospital Clinic Veterinari.

Elisabet Domínguez Miño Elisabet graduated in 2005 from the Universitat Autònoma de Barcelona. She subsequently completed an internship in small animal medicine and surgery at the same university. In 2007 she started a PhD project in laboratory animal diagnostic imaging and obtained the PhD in 2011. In 2011 she enrolled a residency training program in veterinary diagnostic imaging at the Fundació Hospital Clínic Veterinari in Barcelona, which she is currently finishing.

Yolanda Martínez Pereira Yolanda obtained her degree in Veterinary Medicine in 1998 in Spain and after a period in general practice she completed an internship in cardiology obtaining the RCVS Certificate in Veterinary Cardiology (2004). From 2005 to 2008 she completed a residency in Cardiopulmonary Medicine at the University of Edinburgh, followed by a year in the Cardiology Service at the University of Liverpool as a clinician and teacher. During 2009-2012, she joined Borders Veterinary Cardiology Ltd, providing mobile cardiology referral service in Scotland. She returned to the Royal (Dick) School for Veterinary Studies in 2013 as a lecturer in Cardiopulmonary Medicine, heading the service. She obtained her European Diploma in Veterinary Cardiology in 2009 and became RCVS Specialist in Veterinary Cardiology in 2011.

Diagnostic ultrasound in cats

Yvonne Espada Gerlach In 1984 she graduated from the Universidad de Zaragoza. After graduating she developed her PhD project and obtained the PhD in 1990 from the Universitat Autònoma de Barcelona (UAB). She began to work in diagnostic imaging in 1990 performing trainings in several Diagnostic Imaging Services since then, in Paris (Alfort), United Kingdom (Royal Veterinary College and Animal Health Trust), Germany (Giessen) and in the United States (Virginia Tech University). She became a lecturer of the Animal Medicine and Surgery Department of the Universitat Autónoma de Barcelona in 1991 where she is still working as a lecturer currently. In 1992 she started working in the Diagnostic Imaging Service of the Fundació Hospital Clinic Veterinari (UAB) being the Head of the service since then.

Mauricio Tobón Restrepo In 2006 Mauricio Tobón Restrepo obtained his Veterinary Degree from the Universidad de Antioquia (Medellín, Colombia). Immediately afterwards, he worked as a professor of Veterinary Anatomy at the same university. At the same time he was working in private practice. In 2008, he was employed by the Corporación Universitaria Lasallista as a full time professor and director of the veterinary laboratory of anatomy. In 2010, he received his Masters in Education. In 2011 he was given a grant from the Colombian government and the Corporación Universitaria Lasallista to study abroad for his PhD studies. He is finishing his doctoral studies in Animal Medicine and Health at the Universidad Autónoma de Barcelona (Spain) to enroll afterwards as an ECVDI (European College of Veterinary Diagnostic Imaging) resident at the University of Utrecht (The Netherlands). His research line is on feline diagnostic imaging.

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Diagnostic

ultrasound

in cats Rosa Novellas Torroja

Elisabet Domínguez Miño Yvonne Espada Gerlach Yolanda Martínez Pereira Mauricio Tobón Restrepo

Table of contents 1. Ultrasound of the head and neck Scanning technique

5. Ultrasound of the gastrointestinal tract

Ultrasound of the normal head and neck

Scanning technique

Ultrasound in the study of diseases of the head and neck

Ultrasound of the normal gastrointestinal tract

2. Echocardiography Scanning technique

Ultrasound in gastrointestinal tract disorders

6. Ultrasound of the pancreas

Ultrasound of the normal heart

Scanning technique

Ultrasound in disorders of the heart

Ultrasound of the normal pancreas

3. Non-cardiac thoracic ultrasound Scanning technique Normal non-cardiac thoracic ultrasound Ultrasound in thoracic lesions

4. Ultrasound of the liver and biliary system Scanning technique Ultrasound of the normal liver and biliary system Ultrasound in liver and biliary diseases

Ultrasound in pancreatic disorders

7. Ultrasound of the spleen Scanning technique Ultrasound of the normal spleen Ultrasound in splenic disorders

8. Ultrasound of the adrenal glands Scanning technique Ultrasound of the normal adrenal glands Ultrasound in adrenal disorders

9. Ultrasound of the kidneys and ureters Scanning technique

12. Ultrasound of the abdominal cavity, lymph nodes and large vessels

Ultrasound of the normal kidneys and ureters

Scanning technique

Ultrasound in renal and ureteral disorders

Ultrasound of the normal abdominal cavity, lymph nodes and large vessels

10. Ultrasound of the urinary bladder and urethra Scanning technique Ultrasound of the normal bladder and urethra Ultrasound in bladder and urethral disorders

11. Ultrasound of the reproductive system Scanning technique Ultrasound of the normal reproductive system Ultrasound in disorders of the reproductive system

Ultrasound in abdominal cavity, lymph node and large vessel lesions

13. Ultrasound of the musculoskeletal system and superficial soft tissues Scanning technique Ultrasound of the normal musculoskeletal system and superficial soft tissues Ultrasound in alterations of the musculoskeletal system and superficial soft tissues

14. Sampling and other ultrasoundguided procedures General considerations and indications Materials Technique Considerations for sampling and other ultrasound-guided procedures

Diagnostic ultrasound in cats

SCANNING TECHNIQUE The patient can be positioned in dorsal, (left or right) lateral recumbency or a combination of both. In fact it may prove useful to take advantage of the relative positional changes of the gas and fluid in the gastrointestinal tract, particularly when a complete examination of the stomach is required.

[

High-frequency transducers (7.5 MHz or higher) are recommended for gastrointestinal tract examinations. The use of high-frequency linear transducers optimises examination of the intestinal wall layers. Sectorial or micro-convex transducers, with smaller footprints, afford easier access below the costal arch and between the intercostal spaces, thus providing a better view of the cardia, pylorus and the proximal descending duodenum.

While it is recommended that animals should fast before performing ultrasound on the digestive system, it is not too important in cats due to the small amount of gas contained in the feline stomach.

A 12-hour fast is generally recommended to limit interferences from gastric contents, particularly gas and related artefacts, before performing a rigorous ultrasound examination of the stomach. Nevertheless, while this may be a rather common problem in dogs, it is less significant in cats as they have very little gas in their stomachs.

ULTRASOUND OF THE NORMAL GASTROINTESTINAL TRACT Ultrasound can be used to examine the gastrointestinal tract from the cardia to the descending colon (Fig. 1). In some cats both the distal oesophagus and the cardia area are visible at the cranial end of the abdominal midline or displaced slightly to its left. These structures are much easier to identify in sedated or anaesthetised cats.

The stomach is located in the left cranial portion of the abdomen, caudal to the liver. It comprises the gastric fundus (in the left dorsal abdomen), the body of the stomach, the pyloric antrum and the pyloric canal (on the midline and in the ventral abdomen). The pylorus and cranial duodenal flexure are caudal to the hepatic hilum and ventral to the portal vein. The cranial duodenal flexure forms a closed angle in a caudal direction and is located medial to the caudoventral surface of the right liver lobes.

Unlike in dogs, the descending duodenum is found closer to the midline and does not normally come into contact with the abdominal wall. The proximal descending duodenum runs ventral to the caudate lobe of the liver and the right kidney before turning medially at the caudal duodenal flexure. While the ascending duodenum runs cranially 98

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Ultrasound of the gastrointestinal tract

3

1 2

4

6

7 8

Figure 1. Volume rendering reconstruction of an abdominal CT scan of a healthy cat demonstrating the gastrointestinal tract’s normal arrangement. 1: cardia; 2: gastric fundus; 3: pylorus; 4: descending duodenum; 5: jejunum; 6: ileocolic junction; 7: caecum; 8: descending colon. Note that this patient presents a relatively short ascending colon.

5

and is displaced slightly to the left of the midline at which point, after the duodenojejunal junction, it becomes what is known as the jejunum. The path of both the jejunum and the proximal ileum can be followed through the abdomen. The terminal ileum is generally found in the mid-right portion of the abdomen and can normally be followed to the ileocolic junction, where the ileum opens into the colon. The caecum is small, non-compartmentalised and has no gaseous contents. Both the caecum and the ascending colon are located medial to the descending duodenum. After the caecum, the ascending colon continues cranially and for a short section it runs along the right side of the abdomen.

Anatomical variations, with respect to the length and location of the ascending colon, can be encountered in some animals. When this occurs, the ascending colon may be impossible to locate or situated further to the left than usual (see Fig. 1). The colon turns to the left just caudal of the stomach, crossing the cranial abdomen and forming the portion called the transverse colon. Ultrasound can be used to examine the descending colon along the length of the left abdominal wall until it enters into the pelvic cavity. When the descending colon is distended due to faeces or gas it may be displaced to the right of the midline and present a more tortuous path.

The characteristics of the gastrointestinal tract that should be assessed are: overall thickness of the wall, echogenicity, presence of layering, relative thickness of each layer, the pattern of the organ’s lumen, and peristalsis.

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Diagnostic ultrasound in cats

The thickness of the wall varies in each gastrointestinal segment. The ileum is generally considered to be the segment with the thickest walls. Nevertheless, a recent study indicated that this assertion is only correct if the measurement is made at the level of the folds and not between the folds (Di Donato et al., 2014). Contrastingly, the colon is the segment with the thinnest wall. Table 1 presents what are considered normal thicknesses for each segment in a cat’s gastrointestinal tract.

Ultrasound is capable of differentiating between a total of five layers in the gastrointestinal tract. From the inside moving outward; the interface between the lumen of the digestive tract and the mucosa forms a hyperechoic line, the mucosa itself is hypoechoic, the submucosa is a thin hyperechoic line and the muscular layer is hypoechoic. The serosa and subserosa are hyperechoic (Fig. 2). All of the layers should be distinguishable in both transverse and longitudinal views. However, the mucosa does not form a complete circle on transverse views of flattened loops. Instead a hyperechoic line is observed through the mucosal layer on each side of the ultrasound image of the loop. This band constitutes an interface in the mucosa and, in those segments in which the intestinal loops are collapsed, it is due to a greater gap between the villi on both sides of the maximum transverse view of the intestine (Fig. 3) (Rault et al., 2004). No significant differences have been observed in measurements obtained from transverse and longitudinal views of the duodenum and jejunum. Nevertheless, differences in the relative thickness of intestinal layers in each segment of the gastrointestinal system have been reported.

Table 1. Ranges of thicknesses (mm) considered as normal for each gastrointestinal segment.

Newell et al., 1999 (1) Folds Between folds

Goggin et al., 2000 (2)

Winter et al., 2014 (3) Di Donato et al., 2014 (1) Besso et al., 2004 (4)

4.4 ± 0.31 2 ± 0.41

Stomach

2 (1.7–2.2)

1.8 (1.6; 2) 2.2 (1.9; 2.6)

Pylorus

Duodenum

2.4 ± 0.51

Jejunum Ileum

Caecum Colon (1) (3)

2.09 ± 0.37

2.1 (1.9–2.4)

2.1 (1.7; 2.7)

2.2 (2–2.4)

2.4 (2.2; 2.7)

2.2 ± 0.17

2.3 (2.1–2.5)

2.3 (2; 2.5)

2.2 ± 0.18

2.8 (2.5–3.2)

2.8 (2.3; 3.2)

Folds

3.0 ± 0.28

Between folds

2.04 ± 0.17

Proximal

1 (0.7–1.4)

Distal

2.5 (1.5–3.0) 1.7 ± 0.27

1.5 (1.4–1.7)

1.2 (1.2; 1.3)

Data presented as mean values ± SD. (2) Data presented as mean values (95 % confidence interval).

Data presented as median values (1st quartile, 3rd quartile). (4) Data presented as mean values (range).

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Ultrasound of the gastrointestinal tract

Serosa and subserosa Muscularis Submucosa

Lumen-mucosa interface Mucosa

Mucosa

Submucosa Muscularis

Lumen-mucosa interface

a

Serosa and subserosa

b

Lumen-mucosa interface Mucosa Submucosa

Serosa and subserosa Muscularis Submucosa

Muscularis

Mucosa Lumen-mucosa interface

Serosa and subserosa

c

d

Figure 2. Normal differentiation between layers in the gastrointestinal tract. The appearance and relative thickness of the different layers varies in function of the gastrointestinal segment. (a) Transverse view of the fundus presenting a small amount of gas in the lumen. (b) Longitudinal view of several jejunal loops with an intraluminal mucosal pattern. (c) Longitudinal view of the ileum in the vicinity of the ileocolic junction. (d) Longitudinal view of the descending colon with faeces in the intestinal lumen.

Figure 3. Extended mucosal interface. Transverse view of a jejunal loop. A fine hyperechoic line is seen in the centre of the loop, between the lumen and the mucosa, crossing from one side to the other. The mucosa does not form a complete circle.

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Diagnostic ultrasound in cats

Two recent studies analysed the normal thickness of each layer of the different gastrointestinal segments in felines (Di Donato et al., 2014; Winter et al., 2014). The first study, which took into account all of the gastrointestinal segments of 38 healthy cats, concluded that the mucosal layer was thicker than all the other layers in the rest of the segments; the muscular layer was thicker than the submucosa and the serosa, while the submucosa was thicker than the serosa in all segments. The thickest mucosa was found in the duodenum and ileum, while the muscularis layer was thicker in the ileum than in all the other segments (Winter et al., 2014). The second study, which evaluated the small intestine of 20 healthy cats, noted some discrepancies (Table 2) (Di Donato et al., 2014).

Similarly, the ratio between the thickness of the mucosa and the aortic diameter at the level of the coeliac artery, plus the ratio between the muscularis thickness and the aortic diameter (Table 3) have been reported (Winter et al., 2014).

Table 2. Thickness of the layers (mm) in each gastrointestinal segment in healthy cats.

Stomach Fundus

Body

Pylorus

(a)

(a)

(a)

1.2 (1; 1.9)

0.9 (0.6; 1.1)

0.8 (0.6; 1)

Submucosa

0.4 (0.3; 0.5)

0.4 (0.3; 0.5)

0.4 (0.3; 0.5)

Muscularis

0.6 (0.6; 0.9)

0.6 (0.5; 0.8)

0.6 (0.4; 0.8)

Serosa

0.3 (0.2; 0.3)

0.3 (0.3; 0.4)

0.3 (0.2; 0.3)

Mucosa

(a) Winter et al., 2014.

Data presented as median values (1st quartile, 3rd quartile).

Intestine Duodenum

Jejunum

Ileum

Colon

(a)

(b)

(a)

(b)

(a)

Folds (b)

Between folds (b)

(a)

Mucosa

1.4 (1.2; 1.6)

1.27 ± 0.15

1.1 (1; 1.4)

1.2 ± 0.14

1.3 (0.9; 1.5)

0.46 ± 0.08

0.49 ± 0.08

0.4 (0.4; 0.5)

Submucosa

0.3 (0.3; 0.4)

0.36 ± 0.04

0.3 (0.3; 0.4)

0.36 ± 0.04

0.3 (0.3; 0.5)

1.49 ± 0.29

0.53 ± 0.09

0.3 (0.2; 0.3)

Muscularis

0.4 (0.3; 0.5)

0.28 ± 0.07

0.4 (0.3; 0.7)

0.35 ± 0.05

0.8 (0.6; 1)

0.66 ± 0.11

0.65 ± 0.1

0.3 (0.2; 0.3)

Serosa

0.3 (0.3; 0.3)

0.29 ± 0.03

0.3 (0.2; 0.3)

0.31 ± 0.04

0.3 (0.3; 0.3)

0.38 ± 0.08

0.38 ± 0.07

0.2 (0.2; 0.3)

(a) Winter et al., 2014. Data presented as median values (1st quartile, 3rd quartile). (b) Di Donato et al., 2014. Data presented as mean values ± SD.

Table 3. Normal ratio between mucosal thickness and aortic diameter (Ao), and between muscularis thickness and aortic diameter (Winter et al., 2014).

Fundus

Body

Pylorus

Duodenum

Jejunum

Ileum

Colon

Mucosa:Ao ratio (mm)

0.25 (0.20; 0.27)

0.18 (0.12; 0.20)

0.16 (0.12; 0.21)

0.27 (0.22; 0.31)

0.22 (0.20; 0.25)

0.25 (0.19; 0.29)

0.08 (0.07; 0.09)

Muscularis:Ao ratio (mm)

0.12 (0.10; 0.16)

0.12 (0.09; 0.16)

0.11 (0.09; 0.15)

0.079 (0.059; 0.096)

0.087 (0.063; 0.130)

0.14 (0.12; 0.19)

0.05 (0.04; 0.06)

Data presented as median values (1st quartile, 3rd quartile).

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Ultrasound of the gastrointestinal tract

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See video in electronic version Video 1. Oesophageal hiatus (sagittal view of the cranial abdomen)

The lumen of the gastrointestinal tract may contain mucus, gas, fluid, food or faeces.

Each of these elements creates a different ultrasound pattern. The mucous pattern presents an echogenic line without acoustic shadowing (Fig. 4a). Under normal conditions, cats tend to have less gas in their gastrointestinal tracts compared with dogs. However, the amount can increase significantly in the case of diseased animals. Gas will be seen as a hyperechoic surface outlining the gastrointestinal wall, associated with acoustic shadowing and reverberations (Fig. 4b). When these artefacts are observed, only the wall closest to the transducer can be evaluated. Fluid contents within the gastric or intestinal lumen are visible as anechoic to hypoechoic material (Fig. 4c). The echogenicity will vary according to the type of fluid and whether particles of food or small, suspended gas bubbles are present, which are observed as bright points scattered throughout the ultrasound image. Food particles can take on a variable appearance based on their composition and may range from hypoechoic to hyperechoic. Food does not normally cause significant acoustic shadowing, although there are exceptions (Fig. 4d). Faeces are generally accompanied by acoustic shadowing.

a

b

c

d

Figure 4. Intraluminal patterns of the gastrointestinal tract. (a) Longitudinal view of a loop of the small intestine. The intestinal lumen contains a small amount of mucus that appears as a hyperechoic line with no associated artefacts. (b) Longitudinal view of the body of the stomach. On the medial side (left-hand side of the image), a small quantity of gas can be seen producing a dirty shadow, a comet tail and reverberation artefacts. The reverberation artefacts are visible on the left of the image and generate several parallel hyperechoic lines spaced at regular intervals in the far field. The comet tail (arrows) is located between the reverberation artefact and acoustic shadowing. The rest of the gastric lumen presents a mucous pattern. (c) Transverse view of the gastric fundus. The lumen is moderately distended with anechoic fluid. This allows the visualisation of the gastric wall in the far field and creates acoustic enhancement. (d) Transverse view of the fundus with gastric contents. Hyperechoic fluid is visible in the near-field lumen, while food can be observed in the rest of the stomach with a moderate acoustic shadow associated.

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Diagnostic ultrasound in cats

Part of the distal oesophagus can be seen passing through the diaphragm at the level of the oesophageal hiatus (Fig. 5a, Video 1). The cardia can be identified at the level of the gastro-oesophageal junction as a small section with a prominent muscular layer (Fig. 5b, Video 2).

The stomach is easily recognised due to its left cranial position and the presence of gastric folds projecting towards the lumen.

Cats have fewer and thinner gastric folds compared with dogs.

The thickness of the gastric wall varies significantly depending on the degree of gastric distension. Additionally, differences between the measurements of the thickness of the rugal folds and the space between them may be seen. The thickness of the gastric wall should normally be less than 2 mm between rugal folds, and the rugal folds may measure up to 4.4 mm (Newell et al., 1999). When the stomach is empty, its wall is characterised by closely arranged rugal folds, which are best visualised in a sagittal view of the stomach (perpendicular to the axis of the stomach). In a transverse plane, the stomach may have a wagonwheel appearance (Fig. 6a). Evaluating the stomach with a longitudinal view can be complicated as oblique sections through the rugal folds give a false impression of a thickened gastric wall with loss of normal layering (Fig. 6b). Rugal folds are most prominent in the gastric fundus, while the antrum has a smoother wall (Fig. 4b).

KEY POINTS

!

Echogenicity of different intraluminal patterns observed in the gastrointestinal tract of cats An echogenic line without acoustic shadowing is observed in the mucous pattern.

A hyperechoic surface associated to acoustic shadowing and reverberations is seen in the gas pattern.

Food does not tend to cause significant acoustic shadowing.

Faeces are normally accompanied by acoustic shadowing.

a

b Figure 5. Abdominal portion of the oesophagus and the cardia. (a) Longitudinal view of the oesophageal hiatus area. The oesophagus is visible passing through the oesophageal hiatus (arrows). The interface between the diaphragm and the lung can be observed cranial and caudal to the oesophagus, appearing as a hyperechoic line with associated acoustic shadowing. The liver is found in the cranial near field and the stomach in the caudal near field. (b) Longitudinal view of the cardia. The prominent muscularis of the cardia is highlighted between the callipers. Part of the gastric fundus can be seen caudal to the cardia (on the right of the image).

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See video in electronic version Video 2. Cardia (sagittal view of the cranial abdomen)

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Ultrasound of the gastrointestinal tract

a

b

Figure 6. Normal stomach. (a) Transverse view of an empty stomach. The rugal folds protrude towards the lumen of the stomach, creating a wagon-wheel appearance. (b) Longitudinal view of the stomach. Notice that in the middle portion of the stomach the oblique view of the folds hinders the measurement of the actual wall thickness.

Some cats present an accumulation of adipose tissue in the submucosa of the stomach. While it is more easily detected with X-rays or computed tomography (Figs. 7a and 7b) (Heng et al., 2005), in some patients this accumulation can also be detected by ultrasound as a thicker submucosa (Fig. 7c).

b

a

c

Figure 7. Adipose tissue in the gastric submucosa. (a) Ventrodorsal X-ray of the abdomen of a male adult cat. An opaque band of intramural fat is observed on the stomach wall (arrow). (b) Contrast CT of the cranial abdomen. There is a hypoattenuating band (arrow) representing fat between the mucosa (presenting contrast uptake), and the muscular layer and the serosa. (c) Ultrasound of the fundus of the same cat as in (a). The lumen of the stomach contains a moderate amount of gas.

A thick hypoechoic layer can be seen in the submucosa (between callipers).

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Diagnostic ultrasound in cats

The pylorus is also visible between the pyloric antrum and the duodenum, presenting a prominent muscularis (Fig. 8).

In small animals the normal number of peristaltic contractions at the level of the stomach is 4–5 contractions per minute.

In order to locate the duodenum it is important to take into account its anatomical relationships; it can be followed caudally to the pylorus. The major duodenal papilla is typically located close to the pylorus and is a small nodular area situated on the mesenteric margin of the wall (Fig. 9a). No distinct layering or thickness characteristics allow the duodenum (Fig. 9b) to be differentiated from the jejunum. It is important to remember that in obese cats a large portion of the small intestine may be located to the right of the midline. The terminal ileum is situated medial to the descending duodenum and the ileocolic junction is found at its end (Fig. 10a, Video 3). The terminal ileum is further characterised by the presence of a prominent submucosa and muscularis, giving rise to its wagon-wheel appearance (Fig. 10b).

Figure 8. Longitudinal view of the pylorus. The pyloric antrum is on the right of the image and the duodenum on the left. The pylorus (arrows) is found between them, with a prominent muscularis and a somewhat less prominent mucosa.

Figure 9. Duodenum and duodenal papilla. (a) Short

a

b

longitudinal view of the proximal duodenum. The duodenal papilla is visible as a nodular area on the wall of the duodenum (arrow). (b) Longitudinal view of the descending duodenum caudal to the papilla. The descending duodenum is visible in close relationship with the ventral aspect of the right liver lobes, which are visible dorsal to the duodenum in the image. Note that the wall layering and thickness do not allow the duodenum to be differentiated from the jejunum (see Fig. 2b).

Figure 10. Ileum and ileocolic junction. (a) Longitudi-

a

b

nal view of the ileum near the ileocolic junction (between callipers). Note the prominence of the muscularis and submucosa compared to other segments of the small intestine. The colon, which contains gases, is seen to the left of the ileocolic junction. (b) Transverse view of the distal ileum presenting a wagon wheel appearance. Observe the prominent submucosa, thicker at the level of the folds and thinner between folds.

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See video in electronic version Video 3. Ileocolic junction

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