What is the pancreas?
The pancreas is an organ located close to the liver, stomach, and the small intestines. The pancreas has two separate and distinct functions. Its endocrine function is associated with production of the hormones insulin and glucagon to control blood sugar levels. Its exocrine function is to aid in digestion by producing and secreting amylase, lipase, and other digestive enzymes into the gastrointestinal tract.
What types of pancreatic disease may occur?
Functionally, pancreatic diseases are broadly classified into diseases related to the exocrine portion of the pancreas (that is, diseases related to the digestive functions of the pancreas) and diseases related to the endocrine portion of the pancreas (that is, diseases related to the control of blood glucose).
Pancreatitis is a generalized inflammation of the pancreas. Depending on the degree of inflammation, long-term effects can occur to either the exocrine or endocrine pancreatic functions. The underlying cause of pancreatitis is often not known, but it may be related to the recent consumption of a fatty meal, the administration of corticosteroids, inflammatory conditions of the bowel, or direct trauma to the pancreas.
Exocrine pancreatic insufficiency (EPI) is a disorder in which the pancreas fails to produce adequate enzymes for the digestion of fats, carbohydrates, and proteins. This condition can occur in dogs because of previous episodes of pancreatitis, or it may be a congenital or inherited condition. Certain breeds of dogs seem predisposed to developing this problem.
The most common disorder of the endocrine pancreas is diabetes mellitus. This disorder is due to inadequate production of insulin by the beta cells of the pancreas, resulting in high blood sugar.
Rarely, tumors of the pancreas occur. These tumors usually involve the pancreatic beta cells, but other tumors of the pancreas may also occur. See handout “Pancreatic Tumors” for details.
How is exocrine pancreatic disease diagnosed?
The clinical signs a pet exhibits give us the first clue that exocrine pancreatic insufficiency might be present. The lack of enzymes results in poor digestion. A pet with this problem usually produces large quantities of fatty, tan-colored feces and shows gradual weight loss, despite a good appetite.
"A pet with this problem usually produces large quantities of fatty, tan-colored feces and shows gradual weight loss, despite a good appetite."
The most sensitive and specific test for diagnosing exocrine pancreatic insufficiency is trypsin-like immunoreactivity (TLI). This involves taking a single, fasting blood sample that is sent to a veterinary referral laboratory for TLI testing (see handout “Trypsin-like Immunoreactivity” for more information).
Trypsinogen is a proenzyme (a non-activated enzyme) that is secreted by the pancreas into the small intestine, along with other pancreatic digestive enzymes. Upon reaching the small intestine, trypsinogen is converted to trypsin, an enzyme that is involved in the digestion of proteins. A small amount of trypsinogen escapes from the pancreas into the blood circulation and can be measured in a blood sample as trypsin-like immunoreactivity.
Dogs with exocrine pancreatic insufficiency have less trypsinogen being produced because of decreased pancreatic function, and therefore less trypsinogen escapes into the circulation. Trypsin-like immunoreactivity in serum from a dog with exocrine pancreatic insufficiency is often below normal limits. However, if a dog has concurrent pancreatitis or if a sample is taken shortly after a meal, the amount of trypsin-like immunoreactivity may be temporarily increased into the normal range. For this reason, the pet must be fasted prior to testing.
Are there any other tests that may be used to diagnose exocrine pancreatic insufficiency?
There are other tests, but they have been largely replaced by the trypsin-like immunoreactivity test.
Determination of B12 (cobalamin) and folate concentrations in a serum sample may provide supportive evidence of exocrine pancreatic insufficiency.
Both B12 and folate are vitamins that are readily available in most commercial diets, so dietary deficiency is unlikely. Because pancreatic digestive enzymes are required for the proper absorption of B12 from the digestive tract, exocrine pancreatic insufficiency may result in decreased serum concentrations of B12. Folate concentrations may be increased in serum samples from dogs with exocrine pancreatic insufficiency because intestinal bacterial overgrowth accompanying the insufficiency results in increased bacterial production of folate.
How is endocrine pancreatic disease diagnosed?
The endocrine portion of the pancreas is involved in the regulation of blood sugar, accomplished primarily through the effects of the hormones insulin and glucagon. A deficiency in insulin results in diabetes mellitus (sugar diabetes).
Testing for diabetes mellitus is discussed in the handouts "Diabetes in Dogs: Testing and Monitoring" and "Diabetes in Cats: Testing and Monitoring”.
Conversely, too much insulin may be produced if there is a tumor present on the pancreas called an insulinoma. Low blood sugar paired with high insulin levels in the blood, as well as imaging of the pancreas with an ultrasound or CT scan, can diagnose this tumor.
How is pancreatitis diagnosed?
Inflammation of the pancreas (pancreatitis) may occur due to many factors. Certain characteristic laboratory changes support a diagnosis of pancreatitis, in addition to clinical signs that may include vomiting, fever, and abdominal pain.
The complete blood count (CBC) may reveal an increase in the number of white blood cells due to inflammation within the gland. In addition, the packed cell volume (PCV), which is an indication of the total mass that red blood cells are occupying in circulation, may be increased because of dehydration.
The serum biochemistry profile may reveal increases in the pancreatic enzymes amylase and lipase. Amylase and lipase are enzymes involved in the digestion of starches and fats, respectively. Normally, these enzymes are not active until they are secreted into the digestive tract, but with pancreatitis they become prematurely activated and cause damage to the gland and surrounding tissues.
This premature enzyme activation and leakage also results in increased amylase and lipase concentrations in the serum. The increases in amylase and lipase can be variable, however, and other conditions can cause a mild increase (e.g., kidney disease, cancer, gastrointestinal disease, and liver disease). Some animals, especially cats, will not have significant increases in lipase or amylase enzymes in a serum sample, despite having strong clinical evidence of pancreatitis.
The remainder of the serum biochemistry panel may provide additional information regarding the function of other organs, and help identify concurrent conditions.
Are there any other tests that may be used for the diagnosis of pancreatitis?
There is a more specific test for lipase originating from the pancreas in dogs and cats. This test measures the amount of canine pancreatic specific lipase immunoreactivity (cPLI) or feline pancreatic specific lipase immunoreactivity (fPLI) within a serum sample. This test may help distinguish increases in serum lipase values due to pancreatitis from increases due to other causes.
This testing is typically done at a reference laboratory, though there are patient-side tests which can provide a “normal” versus “abnormal” result. For further information, see the handouts "Pancreatitis in Dogs: Pancreas-Specific Lipase" and "Pancreatitis in Cats: Pancreas-Specific Lipase".
Are there any other tests that may be used to assess the pancreas?
Imaging with X-rays does not show the pancreas directly, but there may be changes in the area where it is located. X-rays can also help rule out other causes of clinical signs associated with pancreatic disease (e.g., vomiting and inappetence associated with a bowel obstruction can mimic signs of pancreatitis).
Evaluation of the abdomen with an ultrasound is more helpful in the diagnosis of pancreatitis, especially when laboratory testing fails to provide a definitive answer. Ultrasound can also look for masses, including tumors, cysts, granulomas, or abscesses on the pancreas. A mass on the pancreas, combined with low blood sugar, is indicative of insulinoma.
Surgical or laparoscopic biopsy can be considered if a mass is present, or to definitively diagnose pancreatitis if other testing is inconclusive.
