by Chick Newman PhD, DVM
The pancreas is a multifunctional glandular V-shaped organ located near the stomach and duodenum. The anatomical and functional juxtapositions of the duodenum, stomach, gall bladder (from the liver) and pancreas are shown below:
In addition to its digestive enzyme synthesis and secretion, the pancreas is also an endocrine gland, secreting hormones such as insulin and glucagon for the regulation of blood sugar (see Diabetes). The endocrine functionality of the pancreas will not be addressed on this page.
The most common problems related to the pancreas is pancreatitis (inflammation of the pancreas) and, to a much lesser extent, exocrine pancreatic insufficiency (EPI). Both of these topics will be addressed, though succinctly, on this page.
Pancreatitis, by definition, means inflammation of the pancreas. The types of inflammation have been characterized as 1) edematous/interstitial, 2) hemorrhagic/necrotizing and 3) fibrotic; these represent significant differences in the severity of the disease, from mildest to end-stage (the replacement of inflamed, damaged pancreatic tissue with non-functional connective tissue). All forms of pancreatitis are potentially life-threatening as a result of primary disease and in many cases, the secondary metabolic derangements, including DIC (disseminated intravascular coagulopathy) and shock.
Pancreatitis occurs in response to various insults; these include introduction of a single high-fat meal, hypercalcemia (elevated blood calcium levels), exposure to unusual (for the dog) foods, table scaps, getting into garbage, drugs (azathioprine, L-asparaginase, phenobarbital, bromide, sulfa-containing drugs, tetracycline [rare]), intoxicants (e.g. zinc, organophosphates), confounding medical conditions (e.g. Gastric-dilatation-volvulus, bile reflux disease, hyperlipidemia, pancreatic abcess, pancreatic neoplasia (with duct obstruction)). Stress, obesity and trauma are also risk factors and there are probably other environmental and physiologic factors we do not yet appreciate. Other risk factors include breed (small breeds more at risk than large breeds), previous gastrointestinal disease (non-specific), endocrine disease, such as diabetes mellitus , hyperadrenocorticism, hypothyroidism and surgery. Note: administration of exogenous corticosteroids, heretofor believed to predispose an animal to pancreatitis, is NOT a risk factor as once thought. The pathophysiology of each of these known inciting factors is complex and well beyond the scope of this treatise. It is enough to know that these risk factors and associations to pancreatitis exist.
Signs of pancreatitis in dogs include the following: relatively acute onset of vomiting, diarrhea (possibly bloody), anorexia, abdominal pain, dehydration, and potentially one or more of the following complications: abdominal (fluid) distension, respiratory distress (thoracic fluid accumulation), fever, sepsis (systemic bacterial infection), cardiac arrhythmias and poor circulation/perfusion leading to shock. The appearance of these confounding clinical signs results from the ensuing onset of cardio-vascular collapse from DIC, sepsis, dehydration or all of these.
The diagnosis of pancreatitis in dogs is based in large part upon the results of clinical-pathology data, the physical exam and history, imaging techniques in some instances and if necessary, exploratory surgery with pancreatic biopsy and histopathologic assessment. Other causes of acute vomiting and diarrhea must be ruled out, including infectious and parasitical disease(s), metabolic disease(s) (e.g. liver-gall bladder, kidney, thyroid, adrenal, toxic, peritonitis), anatomical (e.g. foreign body obstruction, gastric dilatation-volvulus, gastrointestinal or splenic torsion, intussception or perforation), trauma.
Some clinical pathology abnormalities thought to be associated with pancreatitis in the dog are:
Fine Needle Aspirate
The treatment goals are to control pain and inflammation, correct fluid deficits and electrolyte imbalances while promoting perfusion (and healing) of the pancreas, gastrointestinal tract and kidneys, assess for and treat DIC ("disseminated intravascular coagulopathy") if present. The treatment of pancreatitis must be tailored to the severity of disease and the ever-changing status of the animal.
Pancreatitis in the cat can present as acute onset of diarrhea, vomiting, inappetance or more commonly, as an insidious, recurring or chronic, intermittent diarrhea, vomiting or both. Either form can be mild or severe. There are several types of acute or chronic pancreatitis in the cat: necrotizing, hemorrhagic with multiple organ involvement, infiltrative (lymphocytic-plasmocytic type of inflammation). In some cats, a suppurative form, involving infectious organisms is seen. In cats with recurrence or persistance, there is often some degree of pancreatic fibosis (end-stage). Additionally, in many cats, there is concurrent inflammation of liver and upper gastrointestinal tissues, a syndrome euphemistically referred to as "triaditis". In the cat, the pancreatic duct, common bile duct and duodenum share the duodenal papilla (see above illustration); the co-involvement of upper intestinal, pancreatic and liver disease is, somehow, believed to be a result of that close association.
Pancreatitis is sometimes seen with diabetes mellitus, vitamin-K-responsive coagulopathy, hepatic (liver) cholangitis-cholangiohepatitis syndrome and what is descriptively termed "inflammatory bowel disease" (IBD). Approximately 38% of cats with Idiopathic Hepatic Lipidosis have concurrent pancreatitis.
Causes of pancreatitis in cats are less well appreciated, compared with dogs. About 90% are "idiopathic", meaning we do not know the underlying cause. However, some known associations predisposing to pancreatitis in the cat include: trauma or ischemia (tissue oxygen deprivation), exposure to organophosphates, infections (FIP, toxoplasmosis,herpes virus, feline distemper (parvo) virus, and liver fluke infestation), hypotension. Unlike the dog, pancreatitis in the cat is not associated with fat intake nor with the exposure to corticosteroids. In cats, pancreatitis can be focal (just specific area(s)) and also chronic-recurring. The latter is an insidious, smoldering form of the disease, an triggers of these episodes are unknown, Owners do not always realize that their cats are having an episode because clinical signs are non-specific. In cats, this form may in some instances be accompanied by hepatitis and/or upper intestinal inflammatory bowel disease (IBD). Remember that the pancreatic duct and common bile duct share a common duodenal papilla (i.e. they may communicate/affect delivery of the other fluid to the intestine). With chronic recurrence of inflammation, there is progressive loss of functional pancreatic tissue (replaced with scar tissue) and eventually some cats become diabetic and, sometimes develop exocrine pancreatic insufficiency (EPI)...where there is insufficient pancreatic proteolytic and lipolytic enzymes to digest complex protein and fat.
The clinical signs of acute pancreatitis in cats may include diarrhea and/or vomiting, lethargy, inappetance, abdominal pain, weakness, hyPOthermia (low body temperature) or hyPERthermia (elevated body temperature). Potential complications and resulting clinical signs in the acute form of the disease are similar to those described for the dog. If acute pancreatitis is severe, the prognosis is guarded. The chronic/recurring form of the disease is most often associated (in order of decreasing frequency) with lethargy, anorexia, dehydration, hypothermia, pain (difficult to discern in many cats), vomting, dyspnea (labored respiration), and lastly, diarrhea.
Diagnosis of pancreatitis in the cat is not easy.
Treatment of feline pancreatitis is similar to that of the dog. However, it is acceptable and useful to give small doses of corticosteroids in some cases of feline pancreatitis (not complicated by diabetes mellitus), in order to quel the intensity of the inflammatory process. Unlike the dog, corticosteroid exposure in cats is not considered a risk factor for the initiation or exacerbation of ongoing pancreatitis. Additionally, in cats it is important to initiate feeding relatively early in the course of the disease, compared to dogs, even in the face of persistent clinical signs. Prolonged anorexia is associated with increased mortality from complications of hepatic lipidosis. Various techniques for feeding anorexic and even vomiting cats are described in the literature including "trickle feeding", syringe feeding, placement of stomach tubes, nasogastric tubes, esophageal tubes, j-tubes, etc, TPN (total parenteral nutrition), PPN (partial parenteral nutrition). These will not be discussed here.
Goals of therapy for acute disease is supportive:
Goal of therapy for chronic recurring disease
Exocrine Pancreatic Insufficiency (EPI) refers to the inadequate production (in the pancreatic acinar cells) and release (via pancreatic duct system) of exocrine pancreatic digestive enzymes. Pancreatic acinar atrophy is the most common cause of EPI in the dog; chronic recurring pancreatitis with resulting scarring of pancreatic tissue is the most common cause in the cat. In some instances of chronic pancreatitis in cats, concurrent diabetes mellitus occurs, due to simultaneous destruction of Islet cells (which synthesize insulin). Other causes of EPI include pancreatic neoplasia, and, rarely, congenital aplasia or hypoplasia of pancreatic acinar cells. Additionally, in German Shepherds and Border Collies a form of immune-mediated pancreatitis, usually subclinical, has been identified that leads to irreversible loss of pancreatic acinar function. Interestingly, the exocrine acinar system normally has a great functional reserve (about 10 fold greater functional ability than is physiologically required for normal digestive needs); this means that greater than 90% of the exocrine pancreas' functionality must be lost before clinical signs are manifest.
In the presence of EPI, the intestine lacks trophic factors...substances required to maintain integrity and absorptive capability. Thus, animals suffer in two ways: 1) inability to digest many foodstuffs due to lack of pancreatic digestive enzymes, and 2) inability to absorb predigested or partially digested nutrients. Nutrients remain in the intestine to feed bacteria, leading to diarrhea and steatorrhea. Malassimilation of nutrients leads to weight loss...sometimes emaciation...with accompanying vitamin deficiencies.
Most affected animals present with polyphagia, severe weight loss and diarrhea. In cats, affected animals may also be seen to vomit and, on occasion, be inappetant. Feces are generally pale, loose, voluminous, greasy and markedly maloderous (due to steatorrhea).
Routine bloodwork is generally not diagnostic; diagnostic imaging is also not particularly useful for diagnosing EPI. Fecal proteolytic active (FPA) can be used; however, samples of frozen feces must be obtained on 3 consecutive days and evaluated for the presence or absence (as with EPI) of proteolytic enzyme activity. If samples are not handled correctly, false positive results (absence of proteolytic activity) suggesting EPI may be obtained.
TLI (trypsin-like immunoreactivity) has suggested as a reliable, specific and sensitive test for EPI in dogs and cats (ACVIM Proceedings 2002, Williams & Steiner). A commercially available elisa test for canine TLI (c-TLI) is available from Diagnostic Products Corporation, 5700 West 96th Street, Los Angeles, CA 90045. Dogs with small intestinal disease other than EPI have normal levels of trypsin-like immunoreactivity whereas, dogs with EPI have little or no detectable activity. According to the paper, this simple test will be positive in cases of EPI even before dramatic clinical signs are apparent. A feline specific TLI (f-TLI) has also been developed and is available at Texas A&M Gastrointestinal Function Test Laboratory. Both canine and feline TLI tests are performed on blood samples obtained from fasted animals. These samples are stable and can be shipped to the testing laboratory via conventional methods.
Usually, supplementing the diet with commercially available pancreatic enzymes is all that is required. Enzymes are mixed with food; preincubation prior to feeding is usually not necessary or beneficial. The enzyme preparations are somewhat expensive and substitution with chopped, raw pancreases of pig, ox or similar species may be economically more acceptable.
One problem faced by a number of patients is that exogenously suppied pancreatic-derived lipase enzymes (which digest fat) may be inactivated when contacted with stomach acid/juices. Preincubation of food with enzymes required for digestion does not improve fat digestion, probably because the optimal conditions for lipase activity occur within the environment of the proximal small intestine, where bile and bile acids, warm temperature and appropriate pH are present. No improvements in lipase activity is seen when gastric acid inhibitors or neutralizers (antacids) were included in the diets of some affected EPI patients. It may be possible to formulate pancreatic enzyme preparations as extended or sustained release preparations, permitting some of the enzyme to reach the small intestine where more optimal conditions exist for fat digestion to occur. No such preparation is yet available, however. Additionally, evidence suggests that high-fiber in the diet may further inhibit pancreatic enzyme activity, suggesting that dietary fiber should be minimal.
Current recommendations are therefore to feed a highly digestible low fiber diet, low in fats. In some instances supplementation with medium chain triglycerides may be beneficial. It has been thought that these can be hydrolyzed by naturally occuring gastic (stomach) lipases and/or can be absorbed intact without the action of pancreatic lipase. There is, however, evidence that even medium-chain triglycerides may require at least some pancreatic lipase activity; therefore, some patients with EPI still might not tolerate this form of dietary supplement.
Vitamin supplementation is also recommended, at least for the intial few weeks (except B12) after diagnosis, as most animals are deficient in B12, vitamins D, E, A and K. In animals in which small intestinal bacterial overgrowth remains a component of continued diarrhea, a short course of appropriate antibiotics may also be warranted. Even in animals supplemented with pancreatic enzymes, injectable vitamin B12 is required for the long term, because the absorption of oral B12 is dependent on species-specific "intrinsic factor" from the pancreas, which is non-functional in these animals.
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