Rare diseases of the exocrine pancreas
8.2.3.1 Pancreatic pseudocyst
A pancreatic pseudocyst is a complication of pancreatitis in human beings, but can also occur secondary to pancreatic trauma and pancreatic neoplasia.14 Recently, several cases of pancreatic pseudocysts in dogs and cats have been described.143,144 A pancreatic pseudocyst is a collection of sterile pancreatic juice, enclosed by a wall of fibrous or granulation tissue.14 The clinical signs are usually nonspecific and mimic those of pancreatitis.145 Vomiting was the most consistent clinical sign in both dogs and cats with a pancreatic pseudocyst.
In some cases, a mass could be palpated in the cranial abdomen. On abdominal ultrasound, a cystic structure in close proximity to the pancreas could be identified (Figure 8.14).145 In most cases described so far, the cystic structure was associated with the left lobe of the pan- creas.143 Aspiration of a pseudocyst is relatively safe and should be attempted for diagnostic and therapeutic purposes.143 In contrast to the fluid from a pancreatic abscess, the drained fluid from a pancreatic pseudocyst should be of low cellularity. If measured, amylase and lipase activity of the aspirated fluid are usually very high. Pancreatic pseudocysts can be treated medically or surgically.145 Surgical correction can involve extirpation of the pseudocyst, external drainage, or internal drainage.146 However, internal drainage is the preferred method of surgical correction and in human patients with a pancreatic pseudocyst extirpation is only recommended in cases where the pseudocyst is small. Medical management of pancreatic pseudocysts involves ultrasound-guided percutaneous aspiration and close monitoring of the size of the pseudocyst. This approach was successful in several cases described in the literature.143 However, it seems prudent to consider surgical intervention in cases in which the clinical signs persist or when the size of the pseudocyst does not decrease significantly over time.8.2.3.2 Pancreatic abscess
A pancreatic abscess is another complication of pancreatitis in human beings.14 A pancreatic abscess is a circumscribed collection of pus, usually in close proximity to the pancreas, containing little or no pancreatic necrosis.14 A bacterial infection may or may not be present. Cases of pancreatic abscesses have been described in dogs and in a single cat, and almost all the cases reported have been sterile.22-24 The clinical signs are nonspecific, but may include vomiting, depression, abdominal pain, anorexia, fever, diarrhea, and dehydration.145 In some patients, a mass in the cranial abdomen could be identified upon abdominal palpation.22 Common clinicopathological findings are neutrophilia with a left shift, elevation of serum amylase and lipase activities, elevations of hepatic enzyme activities, and hyperbilirubinemia.22,23 Abdominal ultrasound shows a hypoechoic structure that can be of variable size and may be irregular (Figure 8.15). Surgical drainage and aggressive anti-
microbial therapy are the treatment of choice in human patients with a pancreatic abscess. Dogs and cats may also respond favorably to surgical drainage.22 However, in one report only 56% of nine patients survived the immediate postsurgical period.23 Thus, given the mixed results and the risks, difficulties, and expenses associated with anesthesia, surgery, and postoperative care, one should avoid surgical intervention unless there is clear evidence of an enlarging mass and /or sepsis in a patient that is not responding well to medical therapy. Also, based on the lack of identifiable infectious organisms, the need for antimicrobial therapy in small animals is questionable unless an organism can be identified upon bacterial culture. However, more patients will need to be studied before more definitive treatment recommendations for dogs or cats with a pancreatic abscess can be made.
8.2.3.3 Pancreatic parasites
Eurytrema procyonis. Eurytrema procyonis, the pancreatic fluke of the cat, can be found in the pancreatic ductular system of foxes, raccoons, and cats.147 These parasites can lead to a thickening of the pancreatic ductular system and to pancreatic fibrosis. Even though a significant decrease of exocrine pancreatic secretion has been shown to occur, cats presenting with clinical signs of EPI secondary to E. procyonis infestation are extremely rare.101 The diagnosis can be made by the detection of the characteristic eggs in fresh feces. Fenbendazole (30 mg/ kg PO q 24 h for 6 consecutive days) has been recommended for therapy.148
Amphimerus pseudofelineus. The hepatic fluke of the cat, A. pseudofelineus can also infest the pancreas, and can lead to pancreatitis.26 Diagnosis can be made on fecal examination by formalin-ethyl acetate sedimentation.149 In one report, treatment with praziquantel (40 mg/kg PO q 24 h for three consecutive days) was successful in the management of an infestation with A. pseudofelineus, but concurrent symptomatic therapy for pancreatitis, as outlined above, also needs to be instituted in these cases.149 The dose of praziquantel recommended for the treatment of this parasite is very high, but is similar to the dose recommended for schistosomiasis in people and praziquantel is considered to have a high therapeutic margin, when administered orally.
8.2.3.4 Pancreatic bladder
A pancreatic bladder, sometimes also referred to as a pancreatic pseudobladder, is an abnormal extension of the pancreatic duct.150,151 Pancreatic bladders can be congenital or acquired. Only a few cats and no dogs with pancreatic bladders have been described in the literature.151 These patients were presented with clinical signs compatible with biliary duct obstruction. Appropriate management has not been studied, but surgical removal may be of most benefit in cases presenting with clinical signs.
8.2.3.5 Pancreatolithiasis
Stone formation within the pancreatic duct system (pancreatolithiasis) has recently been reported in a single cat.151 The cat presented with lethargy, vomiting, diarrhea, hematuria, and weight loss.151 On abdominal ultrasound, there was a suggestion of the presence of two distinct gallbladders, but during an abdominal exploratory, a pancreatic bladder secondary to the obstruction of the duct system was diagnosed.151 The stone was surgically removed and the pancreatic bladder was ex- cised.151 Initially, the patient did well, but after about 1 week the cat deteriorated significantly and was euthanized.151 Pancreatolithiasis has previously been diagnosed in humans and cattle.
8.2.3.6 Pancreatic nodular hyperplasia
Pancreatic nodular hyperplasia (Figure 8.12) occurs quite frequently in older dogs and cats.150 In a recent study, 81 of 101 dogs (80.2%) evaluated at necropsy showed nodular hyperplasia in at least one section.43 The frequency of nodular hyperplasia was correlated with age, but not with pancreatic inflammation, fibrosis, and/or atrophy.43 Disseminated small nodules can be found throughout the exocrine portion of the pancreas. These lesions may be visible during abdominal ultrasound, but differentiation from pancreatitis and pancreatic adenocarcinoma may be difficult.44 During necropsy, pancreatic nodular hyperplasia can be differentiated from pancreatic adenomas by the absence of a capsule in cases of nodular hy- perplasia.152 Nodular hyperplasia does not lead to functional changes and does not cause any clinical signs. It is, therefore, most frequently diagnosed incidentally at necropsy examination of older dogs and cats.
Key Facts
■ Pancreatitis occurs frequently in both dogs and cats and is the most common disease of the exocrine pancreas in both species.
■ Pancreatitis can range in severity and can be subclinical or severe.
Severe pancreatitis is associated with both local and systemic complications.■ When stringent criteria are applied abdominal ultrasound is highly specific for pancreatitis.
■ Serum PLI concentration (Spec cPL™ in dogs and fPLI in cats) is both highly specific and sensitive for pancreatitis in small animals.
■ Treatment of dogs and cats with pancreatitis is dependant on the severity of the disease and may include treatment of the underlying cause, if identified, supportive care, analgesia, antiemetics, nutritional support, plasma, and treatment of concurrent conditions. Also, patients with chronic pancreatitis may benefit from corticosteroid administration.
■ Serum TLI concentration (cTLI in the dog and fTLI in the cat) is the diagnostic test of choice for EPI in both dogs and cats.
■ Patients with EPI can often be successfully managed with pancreatic enzyme replacement therapy and if necessary, cobalamin supplementation, antibiotic therapy, and in some cases antacids.