Canine,Feline
Exocrine pancreatic insufficiency, EPI
Both cats and dogs can be affected by EPI, although it is more common in dogs. Young adult dogs, especially German shepherds, are most likely to be affected with PAA-associated exocrine pancreatic insufficiency. Older dogs and cats affected by EPI will usually develop the disease as a consequence of end-stage chronic pancreatitis.
Exocrine pancreatic insufficiency, or EPI, refers to failure of the pancreas to secrete digestive enzymes normally. This results in a syndrome characterized by diarrhea and weight loss, often despite the presence of a normal or increased appetite. Although EPI can occur in both dogs and cats, the most common cause is different in each species. EPI in dogs is usually due to a condition called pancreatic acinar atrophy, or PAA, but in cats it is most commonly due to end-stage pancreatitis.
Exocrine pancreatic insufficiency is diagnosed on the basis of a blood test. It is treated with pancreatic enzyme replacements, which usually result in improvement of the symptoms. However, if EPI is due to chronic pancreatitis, and is accompanied by diabetes mellitus or other conditions, it can be more difficult to treat successfully.
Clinical signs associated with exocrine pancreatic insufficiency include weight loss, polyphagia, coprophagia, pica, diarrhea, increased borborygmus, and flatulence.
Animals with exocrine pancreatic insufficiency often show weight loss despite having a normal or increased appetite. Many dogs with EPI will have excessive appetites, even for things they normally would not eat, including their own feces. Diarrhea is often present, but will vary in consistency and frequency. Grey colored, oily appearing stools are the classic finding for EPI in young dogs. Increased rumbling sounds are often heard from the abdomen, and many affected animals will pass increased amounts of gas. Occasionally, a long history of intermittent gastrointestinal signs like vomiting, diarrhea, and reduced appetite will be present if EPI is due to recurrent bouts of pancreatitis.
The pancreas serves two major functions. One of these, the endocrine function, is to secrete hormones, particularly insulin. The second major function of the pancreas is to secrete digestive enzymes; this is known as its exocrine function. As the name implies, exocrine pancreatic insufficiency involves abnormalities in the secretion of digestive enzymes. Since enzymes are not available to help digest nutrients, the nutrients cannot be used normally by the body. In addition to the lack of proper digestion of nutrients, exocrine pancreatic insufficiency is accompanied by structural and functional changes in the tissue lining of the small intestine that further impair nutrient absorption.
The most common causes of exocrine pancreatic insufficiency are pancreatic acinar atrophy, or PAA, and chronic pancreatitis. PAA is a disorder that usually affects young adult dogs, particularly German shepherds. Common symptoms include diarrhea and weight loss despite a normal or increased appetite. PAA is not known to occur in cats. Chronic pancreatitis is more commonly a cause of EPI in cats and older dogs. Animals with EPI due to chronic pancreatitis often have diabetes mellitus, since the endocrine portion of the pancreas may also be affected. The symptoms of EPI due to chronic pancreatitis are the same as those caused by pancreatic acinar atrophy. However, additional symptoms like intermittent vomiting and decreased appetite due to pancreatitis, or increased thirst and urination associated with diabetes mellitus, are present as well.
At the present time, the most important diagnostic test for EPI is the measurement of trypsin-like immunoreactivity, or TLI, on a blood sample drawn after a 12-hour fast. Once the diagnosis is confirmed, the main treatment is the oral administration of enzyme replacements, which are usually taken with each meal. Additional treatments, discussed in the treatment section, may be appropriate.
The key diagnostic test for exocrine pancreatic insufficiency is called the serum trypsin-like immunoreactivity test, or TLI. The affected animal's blood sample for this test should be drawn after at least a twelve-hour fast. A low value on this test, accompanied by symptoms consistent with EPI, virtually confirms the diagnosis.
Routine bloodwork and other laboratory tests may help establish the diagnosis of concurrent diseases, but are generally not helpful in diagnosing exocrine pancreatic insufficiency per se. Mild liver enzyme changes, and low serum cholesterol levels may be seen with EPI, but other significant test findings indicate clinical processes other than, or in addition to, EPI.
Treatment of exocrine pancreatic insufficiency is usually necessary for life. Most dogs with EPI due to pancreatic acinar atrophy respond well to enzyme replacement alone, and have a good long-term prognosis. Although affected dogs do not always regain the weight they lost, most of them develop normal stools and no longer continue to lose weight. Animals requiring additional medications to boost the effectiveness of enzyme therapy generally do well.
In cats and in older dogs with EPI due to chronic pancreatitis, the outcome is much less predictable. If other conditions are present, particularly diabetes mellitus, then the prognosis may depend more on the ability to treat these complicating factors successfully.
Less is known about the prognosis of cats with EPI because it occurs much less frequently in felines.
Pancreatic acinar atrophy, or PAA, is the most common cause of exocrine pancreatic insufficiency in dogs. This is common in young adult dogs, but it is not recognized in cats. The underlying cause for PAA is unknown. Nutritional imbalances, pancreatic duct obstruction, toxins, interruption of blood flow to the pancreas, viral infection, immune system abnormalities, and defects in pancreatic development or enzyme secretion have all been suggested as possible causes. PAA can occur in dogs of all breeds and ages; however, due to its relatively higher incidence in young German shepherds, there may be a hereditary contribution to its development in dogs of this breed.
End-stage inflammation of the pancreas, or pancreatitis, may also result in EPI. When this is the case, diabetes mellitus may also be seen due to damage to the endocrine portion of the pancreas. Pancreatitis is more commonly the cause of EPI in cats and older dogs.
The main treatment for exocrine pancreatic insufficiency is the administration of enzyme replacements that are given with each meal. If the diagnosis of EPI is correct, and if sufficient enzyme supplement is provided, diarrhea will begin to resolve in a few days, followed by gradual weight gain in most dogs. It is very important to establish the diagnosis of EPI before starting pancreatic enzyme replacement therapy. Enzyme replacement can be expensive, and usually must be given for the rest of the patient's life. Some animals with diarrhea and a provisional diagnosis of EPI are treated with pancreatic enzyme replacements even when the diagnosis of EPI has not been confirmed. These animals may have resolution of their diarrhea for reasons other than enzyme replacement. If their response to treatment is incorrectly interpreted as confirming the existence of pancreatic insufficiency, they may be kept on an expensive and potentially unnecessary treatment for a long time.
Once an appropriate dose is found that controls the symptoms, the enzyme dose can be reduced until the lowest dose that maintains control is identified. The powder form of enzymes is generally more effective than tablets, although the latter are easier to administer.
Some animals do not respond appropriately to enzyme replacement alone. These patients may benefit from medications that augment enzyme replacement therapy. Certain drugs that block H-2 receptors in the stomach may increase enzyme replacement effectiveness by preventing breakdown of the enzymes in the stomach.
Some dogs seem to do better when they are fed a low fat, low fiber, highly digestible diet, but most dogs do not need specific dietary treatment for EPI. Oral vitamin E supplementation or intramuscular injections of vitamin B-12 may be administered to restore serum concentrations of these substances in dogs with EPI. Although such deficiencies have been documented in EPI, it is not known if they are significant. Rarely, dogs with these vitamin deficiencies that do not respond to enzyme replacement alone will do better when these deficiencies are corrected. Antibiotics may be helpful in some dogs if excessive bacterial growth in the intestines has occurred.
Although cats are treated less often for EPI, similar dietary and vitamin supplementation may be appropriately attempted in certain cats.
There is no known means of prevention of exocrine pancreatic insufficiency. Affected German shepherd dogs should not be bred since EPI may be inherited in that breed.
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