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The pancreas is an organ that plays a vital role in digestion of fats, carbohydrates, and proteins, as well as serves to maintain normal blood glucose levels. It is a small organ that lies near the proximal end of the small intestine. The pancreas is functionally divided into two components; the endocrine and the exocrine pancreas.
The endocrine pancreas constitutes approximately 15% to 20% of the pancreas, and its function is carried out by a group of cells referred to as the islets of Langerhans. The endocrine pancreas is responsible for secreting hormones into the bloodstream that act on a variety of tissues in the body. Three cell types ( α, β, γ ) can be found within the islets.
The predominant cell type is the β cell, which is responsible for producing and secreting insulin. Insulin acts on every organ in the body, and functions to increase energy stores and regulate many important cell functions. It is secreted in response to high blood glucose, and is responsible for maintaining proper blood glucose concentrations. Diabetes mellitus is a disease that occurs due to either lack of insulin production or lack of responsiveness to insulin, and results in prolonged elevated blood glucose levels.
The α and γ cells are less numerous than the β cells, and are responsible for producing and secreting the hormones glucagon and somatostatin, respectively. Glucagon has the opposite effect of insulin, and serves to stimulate the breakdown of energy stores under conditions of low blood glucose. Somatostatin functions to inhibit both insulin and glucagon secretions, and has many other effects on the central nervous system and gastrointestinal system that are beyond the scope of this paper.
While the endocrine pancreas plays a very important role in maintaining homeostasis, it is the exocrine pancreas that will be the focus of this paper. The exocrine pancreas constitutes the majority of the pancreatic tissue and is responsible for the digestive functions of the pancreas. In contrast to the endocrine pancreas which delivers its secretions to its target organs via the bloodstream, secretions of the exocrine pancreas empty into the small intestine via a system of pancreatic ducts. The secretions function to allow for absorption of food contents entering the small intestine from the stomach, as well as maintain an optimal pH for digestive enzyme activity.
The digestive enzymes secreted by the pancreas break down fats, proteins, and carbohydrates, all of which are a normal component of the cells in the body. In order to prevent auto-digestion of the pancreas, these enzymes are secreted in the form of inactive precursors, which then become activated once inside the intestine. Furthermore, present within the pancreas are inhibitors of these enzymes, which serve as an additional safeguard against pancreatic auto-digestion. When circumstances are such that these protective mechanisms fail, damage to the pancreatic cells and subsequent pancreatitis may result (1).
Pancreatitis has been well characterized in the dog, and was historically considered an uncommon feline disease. However, a recent study that was conducted on both healthy and diseased cats suggests that feline pancreatitis may be much more common than previously described (2). It is becoming increasingly recognized in the feline patient, and it is important that both cat owners and veterinary professionals have knowledge of this disease process. The aim of this paper is to highlight the clinical implications of feline pancreatitis.
Pancreatitis is generally classified as being either acute or chronic in nature. Acute pancreatitis implies that the disease process has been going on for a relatively brief period of time, generally days; whereas chronic pancreatitis indicates that the disease process has been going on for a longer time duration. Acute pancreatitis is characterized by necrosis (death) of pancreatic cells without the presence of fibrosis (scar tissue), while chronic pancreatitis is characterized by significant pancreatic fibrosis and atrophy (reduction in functional pancreatic tissue). In the geriatric patient, chronic pancreatitis is the more common form of disease, and will often present as recurring bouts of mild to moderate illness. A third form of the disease is often termed "acute on chronic" and occurs as chronic pancreatitis with evidence of acute inflammation, as well. (1).
In the feline patient, these two disease forms often cannot be differentiated on the basis of clinical signs/symptoms and routine diagnostic testing. However, studies indicate that chronic pancreatitis is the more common form of pancreatitis that occurs in the feline population, representing 65% to 89% of all feline cases (3).
The cause of both acute and chronic pancreatitis is often unknown. Damage to the pancreas can occur due to damage from the pancreatic ducts (for example obstruction or an ascending infection), blood-borne delivery of infectious agents or toxins, or direct traumatic injury (1). Infectious agents such as Toxoplasma gondii and Eurytrema procyonis (pancreatic fluke), toxic agents such as organophosphates, disease conditions such as hypotension and hypercalcemia, and pancreatic cancer have all been implicated in the pathogenesis of pancreatitis. Domestic short hair and Siamese breeds have been postulated to be more susceptible to pancreatitis, and old age is considered to be a significant risk factor. However, the disease process with the greatest association to feline pancreatitis is a syndrome termed "triaditis" (4).
Triaditis is characterized by 3 concurrent disease processes: pancreatitis, biliary tract disease, and inflammatory bowel disease (IBD). In the cat, the pancreatic duct drains into the small intestine in very close proximity to the drainage site for the common bile duct. This is in contrast to the majority of other species, who have a greater degree of separation between the bile and pancreatic ducts. The unique anatomy of the feline pancreatic duct system makes cats susceptible to acquiring pancreatic disease secondary to diseases of the intestine and biliary system. Feline patients will commonly present with varying degrees of all three disease processes (4).
The signs of pancreatitis are often vague and non-specific; furthermore, the feline patient is often very good at disguising illness and pain, making it difficult for the clinician to pinpoint pancreatitis as a suspect disease. The most common signs include lethargy and inappetance. Other signs that may be seen include vomiting, weight loss, diarrhea, and abdominal pain. The most common physical examination findings include dehydration, hypothermia, pale mucous membranes, icterus, and a painful abdomen upon palpation (3,4). If the veterinarian suspects pancreatitis, a number of different diagnostic tests may be performed to aid in diagnosis.
One of the great challenges in a case of feline pancreatitis is reaching/confirming a diagnosis. The tests for pancreatitis are often not very sensitive, meaning that a great number of patients with pancreatitis will have false negative results. They are also often non-specific and can be seen with various other feline diseases.
A complete blood count (CBC), a biochemistry profile, and electrolytes are often the first steps in working up a case of pancreatitis. However, the results of these laboratory analyses are often non-specific and can be found with a number of other feline diseases. Some of these findings may include a non-regenerative anemia (decrease in red blood cells), an increase or decrease in white blood cells (leukocytosis or leucopenia), hypocalcemia (low Calcium), hypokalemia (low potassium), azotemia (elevation in BUN and Creatinine), and elevated liver values. Often, elevated liver values reflect concurrent biliary disease, as is seen with triaditis (4).
Diagnostic imaging of the feline pancreas may be a helpful tool, however, these tests often have low sensitivity and specificity; though diagnostic imaging has proven to be useful in detecting concurrent disease states, such as cholangitis or hepatic lipidosis. Radiography and ultrasonography may be of use in the work-up of a patient with pancreatitis, but a definitive diagnosis is not possible with use of these imaging modalities alone (3).
Laboratory tests specific for pancreatitis or pancreas enzymes have been developed. Currently the most useful of these tests in the feline patient is the feline pancreatic lipase immunoreactivity test (fPLI). This test measures levels of pancreatic lipase, a digestive enzyme that breaks down fat. Patients with pancreatitis often have elevated serum value, as lipase is leaking from the pancreas into the serum. The fPLI is considered to be the most sensitive and specific test for feline pancreatitis, however, it is currently only available through Texas A&M. Other pancreas specific tests that have been used in the past include measurement of serum amylase, lipase, and trypsinogen-like immunoreactivity (TLI); however, these tests have been shown to offer low sensitivity and specificity (4).
Histopathology is the only means of obtaining a definitive diagnosis of pancreatitis, and can be used to differentiate acute from chronic pancreatitis. There are limitations to using this as a diagnostic tool, however, including potential danger to the patient due to invasiveness of the procedure. The clinician should use great caution in determining whether the benefits of obtaining a biopsy outweigh the potential risks to the patient(3,4).
Treatment of the feline patient is aimed toward supportive care, including fluid therapy, proper nutrition, and pain control. The goal of fluid therapy is to restore hydration status and correct electrolyte imbalances. In moderate to severe forms of pancreatitis, the patient will be administered IV fluid therapy. In mild cases, dehydration may be corrected with subcutaneous fluids. Proper nutrition in the feline patient is also imperative, as cats are prone to developing hepatic lipidosis when they become anorexic. At the discretion of the veterinarian, the patient may be offered oral or parenteral (IV) nutrition, depending on whether the cat has had a history of vomiting. Antiemetics are commonly used to control vomiting. Pancreatitis can be very painful for the feline patient, and analgesics, such as buprenorphine, butorophanol, and fentanyl, are commonly used to control pain. Unless bacterial infection is highly suspected to play a role in the pathogenesis of the patient, antibiotics are generally not indicated.
The prognosis of pancreatitis varies greatly for the feline patient. This is due in part to the wide range of severity that can be seen in the feline patient, but also in part due to the difficulty of differentiating acute from chronic pancreatitis. Mild forms of pancreatitis generally carry a good prognosis, while severe forms have a more guarded prognosis. Patients that have concurrent disease such as hepatic lipidosis or severe IBD may also have a poorer prognosis.
Previously, pancreatitis was considered to be primarily a canine disease; however, recent research has allowed us to recognize pancreatitis as a disease of the feline patient, as well. As with any newly discovered disease, the intricacies of the disease process in the cat have not yet been fully characterized. As the scientific and veterinary communities continue to gather more information on the causes and pathogenesis of pancreatitis, we will hopefully obtain more sensitive diagnostic techniques and advanced treatment options that will help us to care for our feline patients.
1. Mcgavin, MD and Zachary, JF. Pathologic Basis of Veterinary Disease. Mosby, Inc. 2007
2. deCook HEV, Forman MA, Farver TB, et al. Prevalence and histopathologic characteristics of pancreatitis in cats. Veterinary Pathology. 44: 39-49. 2007.
3. Warman, S and Harvey,A. Feline Pancreatitis: current concepts and treatment guidelines. Companion Animal Practice. 29:470-477. 2007.
4. Panagiotis, XG and Steiner, JM. Current Concepts in Feline Pancreatits. Topics in Companion Animal Medicine. 23: 185-192. 2008.