Pancreatitis in Cats & Dogs Part 1: Introduction, causes, symptoms & diagnosis

The pancreas (image) is an organ in the body located next to the small intestine just after the stomach. It has two primary functions. It is an integral part of the digestion of food and it is the primary organ responsible for regulation of blood sugar in the body. When the pancreas is diseased, it can result in a very painful and debilitating condition called acute pancreatitis (Image). Disease of the pancreas may also cause diabetes mellitus (sugar diabetes) or chronic pancreatic insufficiency, EPI. (Image) EPI results in the inability of the body to digest foods properly. Pancreatitis has been documented in dogs for many years. Until recently it was not thought to exist in cats. We are now recognizing this disease more frequently in cats due to better diagnostic aids.
A recent study has shown that acute pancreatitis. is almost as frequent in cats as dogs. Chronic forms are more common than acute forms. Pancreatic insufficiency and pancreatic cancer are less common than inflammatory disease. Other forms of pancreatic disease in cats are cysts and pancreatic parasites.
Pancreatitis is inflammation of the pancreas resulting from auto digestion by prematurely activated zymogens.(1) It is the most common disorder of the canine exocrine pancreas and is being diagnosed more frequently in cats as awareness increases and diagnostic tools improve.(1,2) The disease can be classified as acute (reversible following removal of inciting cause) or chronic (irreversible changes from on-going inflammation), and mild or moderate to severe.(1) Cats tend to have more of a chronic disease than dogs.(2) The diagnosis of pancreatitis is usually presumptive, as pancreatic biopsy is not always an option. Although several diagnostic tests have been advocated for use in the diagnosis of pancreatitis, many of them are not sensitive enough to be clinically useful.
The main causes of acute pancreatitis may be caused from an on-going or long-term viral infection, poor diet, stress and from certain medications. Symptoms of acute pancreatitis are similar to chronic pancreatitis. Symptoms of chronic pancreatitis can include, but are not limited to moderate to severe abdominal pain, nausea, fever, reduced mental acuteness, abdominal swelling, weight loss and fatty stools. Symptoms of an acute pancreatitis or inflammation are abdominal pain, nausea, vomiting, weakness, anxiety, fever, abdominal gaseous fullness, abdominal indigestion, chills, fatty stools, anxiety and weight loss.
The Merck Veterinary Manual defines as causes of the disease: “Pancreatitis in dogs can be caused by a high fatty diet, eating a large fatty meal at one sitting, obesity, an underlying condition, some medications, and genetics. For example, some dogs that are fed pork products or dark chocolate develop pancreatitis as a result of the sudden amount of fats that enter the body. In some cases the cause of pancreatitis is termed ‘idiopathic’ meaning the cause of the condition remains unknown.”
Dr. Laura West, D.V.M. and Dr. Frederic Almy, D.V.M. write in their abstract “Diagnosing Pancreatitis in Dogs and Cats by Laboratory Methods”: “The underlying cause of most cases of pancreatitis is usually unknown in both dogs and cats; however, there is a considerable list of associated risk factors. Obese animals as well as animals fed a diet high in fat are more prone to developing pancreatitis.(1,3) Hyperlipidemia has been associated with pancreatitis, although it is unclear whether it is a result of the pancreatitis or part of the cause. Certain breeds of dogs are considered predisposed to developing pancreatitis, such as the miniature schnauzer or terrier breeds.(1,3) A large number of drugs and drug classes have been thought to cause pancreatitis in people, but a direct causal relationship has not been established. Drugs used in veterinary medicine that may be associated with pancreatitis are numerous and include L-asparaginase, azathioprine, estrogen, furosemide, potassium bromide, salicylates, sulfonamides, tetracyclines, thiazide diuretics and vinca alkaloids, among others.(1,3)
Additional causes or risk factors for pancreatitis include exposure to scorpion venom, zinc toxicosis, hypercalcemia, congenital anomalies of the pancreatic duct system, reflux from the duodenum into pancreatic ducts (secondary to surgical creation of a closed duodenal loop, blunt trauma, or vomiting), surgical manipulation (rare), pancreatic ischemia and endocrinopathies (hypothyroidism, diabetes mellitus, hyperadrenocorticism).(1,3)
In cats, toxoplasma gondii and Amphimerus pseudofelineus (hepatic fluke) have an established causal relationship with pancreatitis. Feline infectious peritonitis and panleukopenia have also been implicated. As in the dog, blunt trauma, surgical manipulation and ischemia can result in pancreatitis. Organophosphate intoxication and inflammatory diseases of the liver and intestines are also implicated as causes.(2,3)
In the normal pancreas, proteolytic and phospholipolytic enzymes are synthesized, stored and secreted as inactive zymogens and it is these enzymes that are utilized in the majority of diagnostic tests for pancreatitis. The pancreatic zymogens are only activated once they are cleaved, a process which does not normally occur until they reach the small intestine. Once in the small intestine, enteropeptidases from duodenal enterocytes cleave trypsinogen to make trypsin, which can then activate other zymogens.(1)
Pancreatitis is the end result of a cascade of events but is ultimately caused by the autodigestion of the pancreas.(4) Current literature suggests that this cascade of events begins with a decrease in secretion of pancreatic enzymes in response to some noxious stimulus.(4) Subsequent to the decreased secretory activity, abnormal fusion of lysosomes and zymogen granules results in premature, intrapancreatic activation of trypsinogen.(1,4)
When premature activation of trypsinogen occurs, there are mechanisms in place which limit the activation of other zymogens. First, trypsin is very effective at hydrolyzing itself. Second, pancreatic secretory trypsin inhibitor is synthesized, stored and secreted with the digestive enzymes. If significant activation of trypsin occurs within the acinar cell or duct system, this molecule will inhibit trypsin activity. Additionally, α-macroglobulin and α1-proteinase inhibitor are protease inhibitors in the plasma.1 However, once inhibitory mechanisms are overwhelmed, more zymogens become activated, inflammatory mediators and free radicals are released, and pancreatitis develops.(1)
Common clinical signs in dogs with acute pancreatitis include anorexia (91%), vomiting (90%), weakness (79%), and abdominal pain (58%).(1,5) Abdominal palpation may reveal a cranial abdominal mass.(1,3) A retrospective study of 70 cases of acute canine pancreatitis reported dehydration in 97%, icterus in 26%, fever in 32%, abdominal pain in 58%, and obesity in 43% of dogs at the time of initial examination.(5) Other systemic complications can include respiratory distress, bleeding disorders and cardiac arrhythmias.(1,3)
On the other hand, cats have extremely variable histories and clinical signs. More typical clinical signs include anorexia (97%), lethargy (100%), and dehydration (92%).(6) Vomiting and abdominal pain, while common in the dog, are less frequently reported in the cat (35% and 25%, respectively).(6) Other clinical signs reported include hypothermia, dyspnea, diarrhea, ataxia, and weight loss.(6) Pancreatitis in cats has a tendency to occur with certain other diseases, such as cholangiohepatitis/cholestasis, nephritis, diabetes mellitus, and inflammation or ulceration of the intestines.(2,3)
The cause for acute pancreatitis in most cases is not known. Several cases have been reported that were caused by trauma, abscessation of the pancreas, ingestion of certain food borne toxins, and of pancreatic duct obstruction. In cats, infectious agents such as toxoplasma, herpes virus, FIP, and feline parvo virus may cause pancreatitis. Some cases of liver disease may also cause pancreatitis, such as cholangiohepatitis and fatty liver disease in cats. Clinical signs are non-specific. Fever, rapid heart rate and vomiting, abdominal pain were observed as well as lethargy loss of appetite, and dehydration. Other signs include respiratory distress, and icterus (jaundice). Diagnosis is made by history, clinical signs, x-ray and ultrasonography. The latter is most helpful in the diagnosis. A blood test called the trypsin-like immunoreactivity (TLI) has been very helpful in the diagnosis of the disease. High blood sugar levels are also common with the disease in cats and some cats become diabetic following recovery from acute episodes of pancreatitis. Newer tests are now available, but the tests are still not one hundred percent reliable. Most of the diagnostics are performed by clinical signs. Ultrasound is proving to be invaluable in the process of ruling out other diseases.
The most common cause of pancreatic insufficiency is chronic pancreatitis. With chronic pancreatitis there is an absence of digestive enzymes. Therefore, food will pass through the digestive tract without being absorbed. Thus, a form of malabsorbtion of food occurs. This form of pancreatitis in cats is commonly accompanied by diabetes since both the digestive as well as the insulin producing cells of the pancreas are involved. Clinical signs of chronic pancreatitis include soft, pale and voluminous stools, weight loss, greasy soiling of the area around the rectum, and sometimes the entire hair coat.
Note: Treatment of animals should only be performed by a licensed veterinarian.
Sources:
Merck Veterinary Manual
Laura D. West, DVM and Frederic S. Almy, DVM, MS, Diplomate ACVP
VCA Columbia Animal Hospital
Images: Hill’s pet Food
References
1. Williams DA, Steiner JM. Canine Exocrine Pancreatic Disease. In Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine, Diseases of the Dog and Cat, 6th ed. St. Louis, Elsevier Saunders, 2005, pp. 1482-1487.
2. Steiner JM, Williams DA. Feline Exocrine Pancreatic Disease. In Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine, Diseases of the Dog and Cat, 6th ed. St. Louis, Elsevier Saunders, 2005, pp. 1489- 1491.
3. Simpson, KW. Diseases of the Pancreas. In Tams T. (ed): Handbook of Small Animal Gastroenterology, 2nd ed. St. Louis, W. B. Saunders Co, 2003, pp. 353-365.
4. Steiner JM. Diagnosis of acute pancreatitis. Vet Clin North Am Small Anim Pract 2003; 33: 1181-1195.
5. Hess RS, Saunders HM, Van Winkle TJ, et al. Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in dogs with acute pancreatitis: 70 cases (1986-1995). J Am Vet Med Assoc 1998 Sep1; 213(5): 665-70.
6. Hill RC, Van Winkle TJ. Acute necrotizing pancreatitis and acute suppurative pancreatitis in the cat. A retrospective study of 40 cases (1976-1989). J Vet Intern Med 1993; 7: 25-33.