Features November 2008 Issue

Canine Pancreatitis

Chronic pancreatitis

Chronic pancreatitis

Chronic pancreatitis refers to a continuing, smoldering, low-grade inflammation of the pancreas. Symptoms such as vomiting and discomfort after eating may occur intermittently, sometimes accompanied by depression, loss of appetite, and weight loss. In some cases, signs may be as subtle and nonspecific as a dog not wanting to play normally, being a picky eater, or skipping a meal from time to time. Chronic pancreatitis may periodically flare up, resulting in acute pancreatitis.

Dogs with chronic pancreatitis often respond favorably to a low-fat diet. Pain medication can be helpful in relieving the symptoms of chronic pancreatitis and may speed recovery.

Chronic pancreatitis is often subclinical and may be more common than is generally realized, with symptoms blamed on other diseases. It may also occur concurrently with conditions such as IBD (inflammatory bowel disease) and diabetes mellitus.

Pancreatic functions In addition to digestive enzymes (exocrine function), the pancreas also produces insulin (endocrine function). Dogs who are diabetic may have an increased risk for pancreatitis. Conversely, a dog whose pancreas is damaged due to pancreatitis may develop diabetes, which can be either temporary or permanent; 30 percent of diabetes in dogs may be due to damage from chronic pancreatitis.

Exocrine pancreatic insufficiency (EPI), when the pancreas is no longer able to produce digestive enzymes, can also result from chronic pancreatitis, leading to weight loss despite consuming large amounts of food. When the pancreas is damaged, diabetes is likely to show up several months before EPI.

Causes of pancreatitis

Pancreatitis is often blamed on high-fat diets, though there is little scientific evidence to support this. Active, working dogs, such as sled dogs, can eat as much as 60 percent fat in their diets without developing pancreatitis, but too much fat may cause trouble for middle-aged, overweight, relatively inactive dogs, who are the ones most commonly affected by pancreatitis. Too much fat can also cause problems for some dogs with chronic pancreatitis.

Dietary indiscretion, such as eating rancid fatty scraps from the garbage, can also lead to pancreatitis, particularly when a dog accustomed to a low- or normal-fat diet ingests high-fat foods. That’s why pancreatitis incidents are thought to increase after Thanksgiving, when people may feed their dogs a meal of turkey skin and drippings.

Low-protein diets have also been shown to predispose dogs to pancreatitis, especially when combined with high fat intake. Some prescription diets may be a concern, such as those prescribed to dissolve struvite bladder stones; to prevent calcium oxalate, urate, or cystine stones; and to treat kidney disease; especially for breeds prone to pancreatitis.

Several medications have been associated with pancreatitis, most recently the combination of potassium bromide and phenobarbital used to control epilepsy. This combination has a much higher risk of causing pancreatitis than phenobarbital alone (no studies have been done on the use of potassium bromide by itself).

Many other medications have been linked to pancreatitis, though the relationship is not always clear. These include certain antibiotics (sulfa drugs, tetracycline, metronidazole, nitrofurantoin); chemotherapy agents (azathioprine, L-asparaginase, vinca alkaloids); diuretics (thiazides, furosemide); other antiepileptic drugs (valproic acid, carbamazepine); hormones (estrogen); long-acting antacids (cimetidine, ranitidine); Tylenol (acetaminophen); and aspirin (salicylates).

Corticosteroids, such as prednisone, are especially controversial: while veterinarians have long considered them to be the most common drug to cause pancreatitis, recent human studies have discounted this link. Based on anecdotal evidence, however, I believe the association does exist in dogs. I personally know dogs who developed pancreatitis within days of being given corticosteroids.

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Toxins, particularly organophosphates (insecticides used in some flea control products), as well as scorpion stings and toxic levels of zinc, may also lead to pancreatitis.

Certain conditions may predispose a dog to pancreatitis. These include diabetes mellitus (though it is not clear whether pancreatitis precedes diabetes); acute hypercalcemia (high levels of calcium in the blood, usually from a calcium infusion or poisoning rather than diet or supplements); hyperlipidemia (high fat content in the blood, again usually due to metabolic disorder rather than diet); hypothyroidism; and Cushing’s disease (hyperadrenocorticism).

Both diabetes and hypothyroidism can affect fat metabolism and lead to hyperlipidemia, which may predispose a dog to pancreatitis. Miniature Schnauzers are prone to developing hyperlipidemia and thus may have an increased risk of pancreatitis. Obesity predisposes dogs to pancreatitis, and the disease is often more severe in dogs who are overweight.

Pancreatitis can occur in dogs of any age, breed, or sex. That said, most dogs with pancreatitis are middle-aged or older, overweight, and relatively inactive. Cavalier King Charles Spaniels, Collies, and Boxers have been shown to have an increased relative risk of chronic pancreatitis, and Cocker Spaniels an increased relative risk of acute and chronic pancreatitis combined. Dachshunds have been reported to be predisposed to acute pancreatitis.

Other breeds mentioned as having an increased risk for pancreatitis include the Briard, Shetland Sheepdog, Miniature Poodle, German Shepherd Dog, terriers (especially Yorkies and Silkies), and other non-sporting breeds.

People sometimes develop autoimmune chronic pancreatitis, and it is theorized that dogs may as well. German Shepherd Dogs have been shown to develop immune-mediated lymphocytic pancreatitis, which predisposes them to pancreatic atrophy.

Pancreatitis has been associated with immune-mediated diseases, which may include IBD, though the cause-and-effect relationship is not understood. While there is no scientific evidence to support this, some doctors have suggested that food allergies could be a rare cause of recurrent or chronic pancreatitis. I think IBD could possibly be both a cause and an effect of pancreatitis, or that both could be caused by an underlying autoimmune disease or food allergy.

Dogs with immune-mediated pancreatitis may respond well to corticosteroids such as prednisone, which suppress the immune system, even though this drug has also been thought to cause acute pancreatitis.

Trauma to the pancreas, such as a result of the dog being hit by a car, can lead to inflammation and pancreatitis. Surgery has also been linked to pancreatitis, probably due to low blood pressure or low blood volume caused by anesthesia. Gallstones (choleliths) can block the bile duct, and thus the flow of digestive enzymes from the pancreas and can lead to pancreatitis in people; it is likely that the same would be true for both species (pancreatitis can also block the flow of bile from the gall bladder).

Other theoretical causes include bacterial or viral infections; vaccinations; obstruction of the pancreatic duct; reflux of intestinal contents up the pancreatic duct; impaired blood supply to the pancreas due to shock, gastric-dilatation volvulus (bloat), or other causes; and hereditary factors. In rare cases, pancreatitis can be caused by a tumor in the pancreas.

In most cases with dogs, the cause is never found. In people, pancreatitis is most commonly caused by alcohol abuse.

Next: Confirming the diagnosis

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