26: Pancreas


CHAPTER 26
Pancreas


Cintia R. Oliveira1 and Nathan C. Nelson2


1 VetsChoice Radiology, Madison, Wisconsin, USA


2 Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA


Anatomy


The pancreas consists of two lobes and a body, and is located in close apposition to a number of adjacent organs which efface its margins on radiographs (Figure 26.1). The left lobe is located caudal to the body and fundus of the stomach in the dog. In the cat, the left lobe extends further laterally, toward the hilus of the spleen. It is surrounded by fat and not in contact with other organs, and as a result is routinely seen on abdominal radiographs in cats (Figure 26.2). The remainder of the pancreas is not seen radiographically in cats or dogs when normal.


The pancreas is more readily identified on ultrasound. The body of the pancreas is immediately caudal to the proximal descending duodenum in the dog and cat. The right lobe extends caudally to the medial or dorsal aspect of the duodenum. The right lobe is proportionally longer in the dog compared to the cat, and is reliably seen adjacent to the duodenum on ultrasound, particularly when using a dorsal right intercostal approach (Figure 26.3). The echogenicity of the pancreas is similar to normal liver, and may contact the liver cranially, partially obscuring its margins on ultrasound. In the dog, the pancreaticoduodenal vein may be seen within the right lobe of the pancreas, aiding identification. The left lobe of the pancreas is not often seen in dogs, as gas within the adjacent fundus obscures it. In the cat, the left lobe is readily seen, particularly laterally by the splenic hilus (Figure 26.4). The pancreatic duct is often most evident in the left lobe and usually less than 2 mm diameter, though this diameter increases with age.


The entire pancreas is readily seen on CT images of the dog (Figure 26.5) and cat (Figure 26.6). Given its small size, thin slices (2 mm or less) aid in identification of the pancreas, particularly cranially where it contacts the stomach, colon, and liver. Its attenuation values are similar to the liver and other soft tissue structures.

An illustration of normal pancreatic anatomy showing proximity of the duodenum to the right lobe and the body and the fundus and splenic vein to the left lobe.

FIGURE 26.1 Diagram of normal pancreatic anatomy showing proximity of the duodenum to the right lobe and the body and the fundus and splenic vein to the left lobe.


Pancreatitis in Dogs and Cats


Pancreatitis refers to inflammation of the exocrine pancreas and is the most common exocrine pancreatic disorder in dogs and cats, being divided into acute or acute necrotizing, and chronic [15]. The differences between acute and chronic pancreatitis are histologic and not necessarily clinical.


Acute pancreatitis is associated with varying degrees of inflammation, necrosis, and edema, whereas chronic pancreatitis histologically demonstrates irreversible and progressive fibrosis and acinar loss [25]. Although several causes have been reported, in most cases it is considered idiopathic [24]. Histopathology is the gold‐standard method of diagnosing pancreatitis but is not commonly performed due to its invasive nature. A presumptive diagnosis is usually made by a combination of clinical signs and clinicopathologic and diagnostic imaging findings. Pancreatitis has been reported to be one of the most common causes of portal vein thrombosis in dogs and CT angiography is the gold‐standard method for the diagnosis of portal vein thrombosis [6, 7].


The major radiographic sign of pancreatitis is loss of peritoneal detail with increased soft tissue opacity in the right cranial abdomen which is a result of focal peritonitis (Figure 26.7). Other signs include a mass effect in the right cranial abdomen and a persistent gas‐filled proximal descending duodenum, termed a “sentinel loop sign.” The proximal duodenum may also be displaced ventrally or laterally, appearing to have a broader curvature, and the pylorus of the stomach may be displaced toward the left. However, none of these signs are specific for pancreatitis and radiographs may appear normal.


Ultrasound is usually the imaging modality of choice to diagnose pancreatitis in dogs and cats, but CT has been performed more often recently. Ultrasound findings in acute pancreatitis include an enlarged, possibly mass‐like pancreas with hypoechoic parenchyma, adjacent hyperechoic mesentery, and peritoneal effusion [1810] (Figures 26.826.15). With pancreatic necrosis, there may be irregular hypoechoic and hyperechoic areas and nonenhanced pancreatic tissue [11] (Figure 26.16). The hypoechoic areas within the pancreas are usually caused by inflammation, hemorrhage, necrosis or edema, and the hyperechoic areas are usually caused by fibrosis [2]. Other ultrasound findings include cystic‐like or cavitated lesions, dilation of the pancreatic duct, especially in cats, duodenal or gastric thickening with or without loss of layering and corrugation of the duodenum, and extrahepatic biliary obstruction [1, 9, 10] (Figure 26.10). It is important to remember that dilation of the pancreatic duct in cats can also be associated with aging [12, 13]. Ultrasound may also be normal in cats and dogs and may be normal in the initial stages in dogs [9, 10].


A study evaluating ultrasonographic monitoring in 38 dogs with clinically suspected pancreatitis found that approximately one‐third of the dogs did not have ultrasound findings of acute pancreatitis at the first ultrasound but did on the second examination performed 40–52 hours later [14]. The authors suggested waiting at least 52 hours after admission to perform ultrasound on a dog suspected of having acute pancreatitis [14]. In a study evaluating 25 cats with B‐mode and contrast‐enhanced power and color Doppler ultrasonography of the pancreas, vascularity and blood volume for all Doppler methods were significantly higher in cats with pancreatic disease compared to normal cats [15]. B‐mode ultrasound findings in the diseased cats included hypoechogenicity of the pancreas compared to the liver, irregular contour, presence of masses, nodules or cysts within the pancreas, inhomogeneous pancreas, hyperechoic mesentery, and free fluid. Eight cats in the study had pancreatitis, four had nodular hyperplasia and four had neoplasia. Also in this study, significantly higher values were found with postcontrast compared to precontrast color or power Doppler ultrasound [15].

Photos depict ventrodorsal views of the abdomen (A,C) and close-up images (B,D) of the normal pancreas in two different cats.

FIGURE 26.2 Ventrodorsal views of the abdomen (A,C) and close‐up images (B,D) of the normal pancreas in two different cats. The pancreas can be seen as a fusiform soft tissue opaque structure in the left cranial abdomen between the fundus of the stomach, the spleen, and the left kidney (arrowheads).

Photos depict transverse (short axis) ultrasound images of dogs with a normal pancreas (between the calipers).

FIGURE 26.3 Transverse (short axis) ultrasound images of dogs with a normal pancreas (between the calipers). (A) Using a linear transducer in a small‐breed dog. (B) A large‐breed dog imaged with a macroconvex transducer. The right lobe of the pancreas can be seen as an isoechoic to slightly hypoechoic structure medial or dorsomedial to the descending duodenum. The pancreaticoduodenal vein is seen as a round anechoic structure in the center of the pancreas. In dogs, the right lobe is easier to identify than the left lobe.


In a study evaluating contrast‐enhanced ultrasound (CEUS) of the pancreas in healthy dogs and dogs with acute pancreatitis, the mean pixel and peak intensity of the pancreatic parenchyma in dogs with pancreatitis was significantly higher than that of dogs with normal pancreas, suggesting CEUS can be useful for diagnosing canine pancreatitis and pancreatic necrosis [16]. In a similar study evaluating CEUS in 23 dogs with naturally occurring pancreatitis and 12 normal dogs, of all the parameters evaluated, a significant difference was found only for peak time, with dogs with pancreatitis having a prolonged peak time compared to control dogs [17]. The study suggests CEUS can be used in dogs for the detection of pancreatic perfusion changes as a possible sign of pancreatitis.


Computed tomographic findings are similar, including an enlarged pancreas with ill‐defined borders and homogeneous or heterogeneous enhancement, adjacent peritoneal effusion possibly with fat stranding, thickening of the adjacent duodenum and/or gastric wall, dilated gall bladder and biliary tract due to compression and obstruction by the enlarged pancreas [8, 10, 18] (Figures 26.1426.17). In a study evaluating the use of CT angiography in sedated dogs with suspected pancreatitis, an enlarged homogeneously or heterogeneously enhancing pancreas with ill‐defined margins were the main findings [18]. In addition to these findings, three out of 10 dogs had portal vein thrombi. Not surprisingly, the portal vein thrombi seen with CT was not found on US on any of the dogs (given the challenge of examining the portal vein with US in dogs). The authors also found that three out of four dogs with heterogeneous enhancement had overall poorer outcome compared to the dogs with homogeneous enhancement, concluding that the heterogeneous enhancement may correspond to necrotic or fibrotic nonenhancing regions in the pancreas. However, the overall number of dogs with heterogeneous enhancement is very small and a larger number of cases would need to be studied for meaningful conclusion of this finding [18].

Photos depict sagittal (long axis) ultrasound images of a cat with normal pancreas.

FIGURE 26.4 Sagittal (long axis) ultrasound images of a cat with normal pancreas. (B) is a close‐up of (A), (E) is a close‐up of (D). The left lobe of the pancreas (AE) can be seen as a fusiform isoechoic to slightly hypoechoic structure medial or dorsomedial to the spleen (on (B) the green line indicates the pancreas diameter). It is also caudal to the stomach and cranial to the transverse colon. In cats, the left lobe and body of the pancreas are easier to identify than the right lobe.

Photos depict transverse plane postcontrast CT images of the abdomen of a 10-year-old poodle with a normal pancreas.

FIGURE 26.5 Transverse plane postcontrast CT images of the abdomen of a 10‐year‐old poodle with a normal pancreas. (A) Left lobe of the pancreas (arrow). (B) Body of the pancreas (closed arrowheads). (C) Right lobe of the pancreas (open arrowhead).


Another study compared the use of computed tomography angiography (CTA) with ultrasound in the diagnosis of acute pancreatitis in dogs and concluded that CTA did not significantly identify pancreatitis better than ultrasound. However, it allowed visualization of the entire pancreas and detected portal vein thrombosis and biliary mineralization significantly better than ultrasound [10].


Acute pancreatitis has been associated with pulmonary complications in dogs [19, 20]. A study evaluated 26 dogs presenting with acute pancreatitis and found 21 of the 26 had clinical and radiographic signs of pulmonary disease, including alveolar and interstitial pattern, indicative of acute lung injury or pneumonia [20]. In a study evaluating the accuracy of CT for the diagnosis of feline pancreatitis, only two of the 10 cats had CT changes consistent with pancreatitis, which were described as enlarged pancreas and reduced contrast in the surrounding fat in one of the cats [21]. In this study, visualization of the pancreas was considered difficult on CT and not possible without intravenous contrast administration. In a recent study evaluating 21 cats with pancreatitis, the pancreas was seen on CT in 18 out of 19 cats, but differences in pancreatic dimensions were not seen in cats with pancreatitis compared to normal cats. Measurements included diameter, contour, enhancement, and pre‐ and postcontrast density [8]. These two studies suggest lack of support for the use of CT in the diagnosis of pancreatitis in cats [8, 21].

Photos depict tranverse CT image of the body (A), left lobe (B), and dorsal image of the left lobe (C) of a normal pancreas in a cat.

FIGURE 26.6 Tranverse CT image of the body (A), left lobe (B), and dorsal image of the left lobe (C) of a normal pancreas in a cat. The pancreas is indicated by closed arrowheads. The body of the pancreas is ventral to the portal vein (open arrowhead). The left lobe extends immediately cranial to the colon and caudal to the stomach, and is ventral to the splenic vein (arrow). The pancreatic duct is seen in the left lobe.


There are very few reports on the use of magnetic resonance imaging (MRI) for evaluation of the pancreas. With MRI, the pancreas is assessed by evaluating the intensity changes on T1‐ and T2‐weighted sequences, the contrast enhancement, the presence of pancreatic and common bile duct dilation, and by evaluating the surrounding soft tissues for the presence of fluid and inflammation indicating peritonitis. Magnetic resonance cholangiopancreatography has been used to image the biliary tract and pancreatic duct in normal cats and in cats with cholangitis and pancreatitis [22]. MRI findings in cats with pancreatitis included enlargement, pronounced signal intensity abnormalities with T1 precontrast hypointense and T2 hyperintense pancreatic parenchyma (normal pancreas in cats is T1 hyperintense and T2 hypointense), contrast enhancement, and dilated pancreatic duct [22].

Photos depict right lateral (A), left lateral (B), and ventrodorsal (C) views of the abdomen of a 10-year-old mixed-breed dog.

FIGURE 26.7 Right lateral (A), left lateral (B), and ventrodorsal (C) views of the abdomen of a 10‐year‐old mixed‐breed dog. The owners found it laterally recumbent. Septic peritonitis was diagnosed by ER service via abdominocentesis. There is generalized poor peritoneal detail with multiple small free gas bubbles (closed arrowheads). A large, poorly defined soft tissue opaque mass is present caudal to the stomach on the lateral views ((A,B) open arrowheads), and there is increased soft tissue opacity on the right cranial abdomen on the VD view ((C) arrow). Differentials include neoplasia, abscess, or granuloma possibly from spleen, pancreas, or liver. An abdominal exploratory surgery revealed an approximately 5 × 4 cm mass with purulent exudate effacing the left lobe of the pancreas and extending into the root of the mesentery with a focal area of necrosis. There was generalized peritonitis and large amounts of serosanguinous fluid. The primary differential diagnosis was necrotizing pancreatitis. The patient was euthanized, and a final histologic diagnosis was not obtained.


The diagnosis of chronic pancreatitis is very challenging, and the differentiation of acute and chronic pancreatitis may also be challenging [14]. With chronic pancreatitis, radiographs are usually normal. With ultrasound, the pancreas may be normal or decreased in size, with mixed echogenicity, nodular lesions and hyperechoic shadowing lesions corresponding to fibrosis and/or mineralization [1, 9, 10]. In cats, enlargement or irregularity of the pancreatic ducts may be seen as well as dilated common bile duct if there is partial or complete common bile duct obstruction. Pancreatitis in cats may be seen associated with hepatic lipidosis, cholangitis, diabetes mellitus or inflammatory bowel disease [3, 4].


Concurrent pancreatitis, inflammatory bowel disease, and hepatic lipidosis is a medical condition in cats called triaditis [3, 4]. Ultrasound signs associated with triaditis in addition to those seen with pancreatitis include diffuse hyperechoic liver and changes in the small intestine layering and/or thickness (see Triaditis below).


Pancreatitis cannot be reliably differentiated from pancreatic neoplasia based on imaging alone and sampling is needed for definitive diagnosis.

Photos depict transverse (short axis (A–C)) ultrasound images of a 4-year-old cockapoo presented for inappetence, vomiting, and lethargy.

FIGURE 26.8 Transverse (short axis (AC)) ultrasound images of a 4‐year‐old cockapoo presented for inappetence, vomiting, and lethargy. The left and right lobes of the pancreas are severely enlarged and hypoechoic (arrowheads (A,B)). Multiple hyperechoic regions are also present in the pancreas (C). There is a large amount of anechoic free fluid in the abdomen and the mesentery is hyperechoic (D). A fine needle aspiration of the pancreas was performed. The cytologic diagnosis was pancreatitis.

Photos depict sagittal (long axis) ultrasound images of the left lobe (A,B) and body (C) of the pancreas of a 12-year-old DSH presented for further workup of chronic vomiting.

FIGURE 26.9 Sagittal (long axis) ultrasound images of the left lobe (A,B) and body (C) of the pancreas of a 12‐year‐old DSH presented for further workup of chronic vomiting. Blood work showed abnormal fPLI. The left lobe and body of the pancreas (arrowheads) are hypoechoic and enlarged with surrounding hyperechoic mesentery. A small amount of free fluid was present. The findings are suggestive of acute pancreatitis.

Photos depict transverse (short axis (A–G)) ultrasound images of a 11-year-old mixed-breed dog presented to the emergency service for lethargy, weight loss, inappetence, and a distended abdomen.
Photos depict transverse (short axis (A–G)) ultrasound images of a 11-year-old mixed-breed dog presented to the emergency service for lethargy, weight loss, inappetence, and a distended abdomen.

FIGURE 26.10 Transverse (short axis (A–G)) ultrasound images of a 11‐year‐old mixed‐breed dog presented to the emergency service for lethargy, weight loss, inappetence, and a distended abdomen. The right (AC) and left (D–G) lobes of the pancreas are enlarged and hypoechoic (arrowheads). A small amount of free fluid is present, and the surrounding mesentery is hyperechoic. The pancreatic duct is mildly dilated, measuring 0.3 cm in diameter ((C) open arrowhead). The patient underwent exploratory surgery for biopsies due to severely elevated liver enzymes. On surgery, the pancreas was enlarged and the liver was fibrotic with multiple nodules. Histopathology of the pancreas revealed subacute pancreatitis with necrosis, edema, hemorrhage, and evidence of chronic pancreatitis with pancreatic acinar fibrosis and degeneration. No infectious organisms or neoplastic cells were visualized in the pancreas. The patient was also diagnosed with cirrhosis and Cushing disease.

Photos depict transverse (short axis (A–C)) and longitudinal (long axis (D)) ultrasound images of a 11-year-old goldendoodle presented for acute onset of vomiting, anorexia, and extreme lethargy.

FIGURE 26.11 Transverse (short axis (AC)) and longitudinal (long axis (D)) ultrasound images of a 11‐year‐old goldendoodle presented for acute onset of vomiting, anorexia, and extreme lethargy. The right lobe of the pancreas is enlarged and heterogeneously hypoechoic (arrowheads) with some hyperechoic regions. A small amount of free fluid is present, and the mesentery is hyperechoic. The findings are suggestive of acute pancreatitis, possibly with a component of chronic pancreatitis. Pancreatic neoplasia cannot be ruled out.

Photos depict transverse (short axis) ultrasound images of the body (A,B) and left lobe ((C,D) magnified) of an 8-year-old Border collie presented for persistent hypercalcemia and suspect lymphoma.

FIGURE 26.12 Transverse (short axis) ultrasound images of the body (A,B) and left lobe ((C,D) magnified) of an 8‐year‐old Border collie presented for persistent hypercalcemia and suspect lymphoma. The pancreas is mildly enlarged and hypoechoic (closed arrowheads) with multiple ill‐defined hypoechoic nodules (open arrowheads). The findings are suggestive of acute pancreatitis with concurrent nodular hyperplasia or neoplasia. A final diagnosis was not obtained.

Photos depict transverse (short axis (A–D)) ultrasound images of a 7-year-old mixed-breed dog presented with vomiting.

FIGURE 26.13 Transverse (short axis (AD)) ultrasound images of a 7‐year‐old mixed‐breed dog presented with vomiting. The right lobe of the pancreas is diffusely and moderately enlarged and hypoechoic (closed arrowheads). Some hypoechoic nodules are present ((D) open arrowheads). The surrounding mesentery is hyperechoic. The findings are suggestive of acute pancreatitis with nodular hyperplasia and steatites. Pancreatic neoplasia cannot be completely ruled out.


Triaditis


Triaditis refers to feline inflammatory gastrointestinal disease due to concurrent inflammation of the small intestines, pancreas and hepatobiliary system, and has been reported in 50–56% of cats with pancreatitis [3, 4

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Jul 15, 2023 | Posted by in ANIMAL RADIOLOGY | Comments Off on 26: Pancreas

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