What the Pancreas Normally Does:

The pancreas is a small light pink glandular organ nestled under the stomach and along side the duodenum (upper small intestine). The "endocrine" pancreas is the part of the pancreas that secretes hormones such as insulin and glucagon which regulate blood sugar. The "exocrine" pancreas produces enzymes we use to digest our food. These two parts of the pancreas are not in separate areas but instead these two different types of pancreatic tissues are all mixed together throughout the entire pancreas.

Digestive enzymes include amylase to digest starches, lipases to digest fats, and  trypsin and proteases to digest protein.  They are stored in inactive forms inside special granules in the exocrine pancreatic tissue (the “acinar cells” ) and are secreted into the duodenum (the first part of the small intestine after the stomach) when ground up food begins its passage out of the stomach.  Once nutrients are broken down into smaller molecules (i.e. they are digested), they can be absorbed down the entire length of the GI tract.  Without adequate productive of these enzymes, we cannot digest our food. If we cannot digest the food, we cannot absorb the food. We get skinny, have especially nasty rather greasy diarrhea, or both. Often, a dog will develop a dry, dandruffy coat from inability to absorb dietary fats.

Exocrine Pancreatic Insufficiency (also called “Maldigestion”)

The most common cause of digestive enzyme deficiency in dogs is “pancreatic acinar atrophy,” where the pancreas simply is shriveled and useless. This condition seems to have a genetic basis but is not congenital and may develop at any age (though usually shows up before age 4 years). The German Shepherd Dog and Rough-Coated Collie are particularly at risk and the mode of inheretance appears to be autosomal recessive and involves immune-mediated destruction of the pancreas. About 70% of dogs with exocrine pancreatic insufficiency are German Shepherd dogs and 20% are Rough Collies.

In the cat, chronic pancreatitis is the usually cause of exocrine pancreatic insufficiency. There does not appear to be a genetic concern.

Diagnosis Requires Specific Tests

The biggest breakthrough in the diagnosis of Exocrine Pancreatic Insufficiency was the development of the Serum Trypsin-like Immunoreactivity test, a blood test. Prior to this, an assortment of inaccurate fecal tests were utilized. The TLI test looks for a normal level of trypsin-like enzymes in the bloodstream. In the normal animals, trypsin, an enzyme of protein digestion, is stored in the pancreas in an inactive form so as to avoid digestion of one’s own body. Still, trace amounts of active enzyme make it into the bloodstream. This is harmless, normal, and detectable. A dog or cat with EPI will have almost no Serum Trypsin-like Immunoreactivity in the bloodstream. The patient must be fasted for the test to be accurate but only a single blood sample is needed to make the diagnosis. The feline version of this test often requires that the sample be sent to a university laboratory and generally a week or so is needed to get results but the canine test can be run in just a few days.

Another popular test is the Fecal Protease Test, where a stool sample is tested for protein digesting enzymes. Fasting is not necessary and any fecal sample will do; however, 3 consecutive samples are needed to get a consistent result as there is tremendous variability in fecal enzyme activity over the day. Sometimes soybeans are given to dogs to help stimulate release of pancreatic protein digestion enzymes and get a more accurate test.

The Fecal Elastase test (elastase being another digestive enzyme) is the newest test and it is only available for dogs. A single fecal sample is needed but the problem is that some times normal dogs will test negative for Elastase. This means that EPI can be ruled out when the Elastase test is positive but not confirmed when the Elastase test is negative.

Treatment

Dietary supplementation with digestive enzymes is an effective therapy for EPI even though most of the supplement given is digested in the stomach along with other dietary proteins. The little bit that survives the acid bath of the stomach and its own protein-digesting chemicals turns out to be enough to stop the diarrhea and enable the patient to actually gain some weight. Powdered enzymes (Viokase-V, Pancreazyme) seem to work the best though tablets are also available and some like to give raw chopped beef, or lamb pancreas. In the past, it was suggested that incubating the enzymes in the patient’s food would help initiate the digestion process in the food bowl but this has not been found to be true; the enzymes can be fed immediately mixed with the patient’s regular pet food. Some patients respond best when an H2 blocker-type antacid (such as famotidine) is given concurrently with the enzymes.

Generally a high digestibility diet is the best choice for an EPI patient. These foods are low in fiber and fat and may be especially helpful for patients with trouble gaining weight. Many animals simply use enzymes mixed with their regular food.

EPI patients commonly have an overgrowth of bacteria in their intestines which means that the unabsorbed nutrients in the tract have fed the bacteria living there (instead of the patient) and an overpopulation has occurred. This results in a vitamin B-12 deficiency as the bacteria consume the vitamin (instead of the patient getting some). A course of antibiotics is helpful to correct this problem especially early in the course of treatment. Periodic injections of vitamin B-12 have been recommended for patients with EPI.

Treatment is for life and without enzyme supplementation, all the unpleasant symptoms will recur. The good news is that a response to therapy is generally seen within a week of beginning therapy. Response can be excellent but approximately one dog in 5 will simply not respond well. Many do not ever regain a normal amount of weight.