The exocrine pancreas is a portion of this organ that contains clusters of ducts (acini) producing bicarbonate anion, a mild alkali, as well as an array of digestive enzymes that together empty by way of the interlobular and main pancreatic ducts into the duodenum (upper small intestine). The hormones gastrin, cholecystokinin and secretin are secreted by the stomach and duodenum in response to distension and the presence of food, and in turn stimulate the production of digestive enzymes by the exocrine pancreas. The alkalization of the duodenum neutralizes the acidic chyme produced by the stomach that is passing into it; the digestive enzymes serve to catalyze the breakdown of complex foodstuffs into smaller molecules for absorption and integration into metabolic pathways. The enzymes include proteases (trypsinogen and chymotrypsinogen) and hydrolytic enzymes that cleave lipids (the lipasesphospholipase A2 and lysophospholipase, and cholesterol esterase). EPI results from progressive failure in the exocrine function of the pancreas to provide its digestive enzymes, often in response to a genetic condition or other disease state, resulting in the inability of the animal involved to properly digest food (maldigestion) and to subsequent malabsorption of nutrients.
In humans, the most common causes of EPI are chronic pancreatitis and cystic fibrosis, the former a longstanding inflammation of the pancreas altering the organ's normal structure and function that can arise as a result of malnutrition, heredity, or (in the western world especially), behaviour (alcohol use, smoking), and the latter a recessive hereditary disease most common in Europeans and Ashkenazi Jews where the molecular culprit is an altered, CFTR-encoded chloride channel. In children, another common cause is Shwachman-Bodian-Diamond syndrome, a rare autosomal recessive genetic disorder resulting from mutation in the SBDS gene.
EPI is often treated with pancreatic enzyme replacement products (PERPs) such as pancrelipase, that are used to break down fats (via a lipase), proteins (via a protease), and carbohydrates (via amylase) into units that can be digested by those with EPI.
In animals, signs of EPI are not present until 85 to 90 percent of the pancreas is unable to secrete its enzymes. In dogs, symptoms include weight loss, poor hair coat, flatulence, increased appetite, coprophagia, and diarrhea. Feces are often yellow-gray in color with an oily texture. There are many concurrent diseases that mimic EPI and severe pancreatitis is one that if allowed to continue unabated can lead to EPI.
The most reliable test for EPI in dogs and cats is serum trypsin-like immunoreactivity (TLI). A low value indicates EPI. Fecal elastase levels may also be used for diagnosis in dogs.
In dogs, the best treatment is to supplement its food with dried pancreatic extracts. There are commercial preparations available, but chopped bovine pancreas from the butcher can also be used (pork pancreas should not be used because of the rare transmission of pseudorabies). Symptoms usually improve within a few days, but lifelong treatment is required to manage the condition. A rare side-effect of use of dried pancreatic extracts is oral ulceration and bleeding.
Because of malabsorption, serum levels of cyanocobalamin (vitamin B12) and tocopherol (vitamin E) may be low. These may be supplemented, although since cyanocobalamin contains the toxic chemical cyanide, dogs that have serious cobalamin issues should instead be treated with hydroxocobalamin or methylcobalamin. Cyanocobalamin deficiency is very common in cats with EPI because about 99 percent of intrinsic factor (which is required for cyanocobalamin absorption from the intestine) is secreted by the pancreas. In dogs, this figure is about 90 percent, and only about 50 percent of dogs have this deficiency. Cats may suffer from Vitamin K deficiencies. If there is bacterial overgrowth in the intestine, antibiotics should be used, especially if treatment is not working. In dogs failing to gain weight or continuing to show symptoms, modifying the diet to make it low-fiber and highly digestible may help. Despite previous belief that low-fat diets are beneficial in dogs with EPI, more recent studies have shown that a high-fat diet may increase absorption of nutrients and better manage the disease. However, it has been shown that different dogs respond to different dietary modifications, so the best diet must be determined on a case-by-case basis.
One possible sequela, volvulus (mesenteric torsion) is a rare consequence of EPI in dogs.
^Clark L, Wahl J, Steiner J, Zhou W, Ji W, Famula T, Williams D, Murphy K (2005). "Linkage analysis and gene expression profile of pancreatic acinar atrophy in the German Shepherd Dog". Mamm Genome16 (12): 955–62. doi:10.1007/s00335-005-0076-1. PMID16341675.
^Wiberg M, Saari S, Westermarck E (1999). "Exocrine pancreatic atrophy in German Shepherd Dogs and Rough-coated Collies: an end result of lymphocytic pancreatitis". Vet Pathol36 (6): 530–41. doi:10.1354/vp.36-6-530. PMID10568434.
^Kim J, Jung D, Kang B, Kim H, Park C, Park E, Lim C, Park H (2005). "Canine exocrine pancreatic insufficiency treated with porcine pancreatic extract". J Vet Sci6 (3): 263–6. PMID16131834.
^Steiner J, Rutz G, Williams D (2006). "Serum lipase activities and pancreatic lipase immunoreactivity concentrations in dogs with exocrine pancreatic insufficiency". Am J Vet Res67 (1): 84–7. doi:10.2460/ajvr.67.1.84. PMID16426216.