Originally published in the August 2015 issue of Veterinary Practice News. Loved this article? Then subscribe today!
Pancreatic lipase immunoreactivity, or PLI, is the most accurate laboratory test for diagnosing pancreatitis in dogs and cats, experts say.
Accurately identifying this gastrointestinal malady has long baffled practitioners. Pancreatic biopsy is considered the gold standard diagnostic test for pancreatitis, but it is uncommonly performed due to the invasiveness and expense of the surgery.
Most clinical cases can be diagnosed with a combination of a compatible history and clinical signs, and with the serum PLI and abdominal ultrasound, said Steve Hill, DVM, MS, of Veterinary Specialty Hospital of San Diego.
“Routine serum amylase and lipase levels, which are commonly part of general chemistry panels, have limited utility in diagnosing pancreatitis due to their low sensitivity and specificity in both dogs and cats,” said Dr. Hill, a diplomate of the American College of Veterinary Internal Medicine, small animal, and the immediate past president of the Comparative Gastroenterology Society.
“The most accurate laboratory diagnostic test is the pancreatic lipase immunoreactivity, which measures pancreas-specific lipase and has very good sensitivity and specificity for acute and chronic pancreatitis,” he said.
The PLI test for dogs and cats is commercially available through Idexx Laboratories Inc. as an in-house SNAP test and as a Spec PL, which gives a quantitative value and is run as a send-out test to Idexx.
“The SNAP PL is a point-of-care test that is highly accurate when negative, but when positive, should be confirmed with the send-out Spec PL,” Hill said. “The Spec PL gives a quantitative value.”
Andrew Hanzlicek, DVM, MS, small animal professor at Oklahoma State University’s Center for Veterinary Health Sciences, said diagnosing pancreatitis is inherently frustrating because, “The clinical signs are not specific. They overlap with other gastrointestinal diseases. In addition, there is no perfect diagnostic test. The diagnosis is a combination of clinical findings.”
Pancreatitis is an inflammatory condition of the exocrine pancreas which occurs frequently in both dogs and cats, according to an article by Jorg Steiner, Dr. med. vet., Ph.D., Dipl. ACVIM, and director of the Gastrointestinal Laboratory at Texas A&M University’s College of Veterinary Medicine and Biological Sciences.
In a study of 70 dogs with fatal pancreatitis, clinical signs in descending order of frequency included anorexia, vomiting, weakness, abdominal pain, dehydration and diarrhea.
Cats presented with less specific signs, Steiner wrote, citing a separate study of a “large number” with symptoms that included anorexia, lethargy, dehydration, weight loss, vomiting, hypothermia, icterus, fever, abdominal pain, diarrhea or a palpable abdominal mass.
“Most cases of pancreatitis in dogs and cats are idiopathic — cause unknown — and the most common association found in dogs is dietary indiscretion or ingestion of a high-fat meal,” Hill said. “Pancreatitis can also occur post-abdominal surgery; with trauma; with pancreatic hypoperfusion; and in patients with hypertriglyceridemia, common in miniature schnauzers.”
The disease also can occur secondarily to such endocrine conditions as diabetes mellitus and Cushing’s disease, which cause hypertriglyceridemia; and due to certain drugs, including azathioprine, potassium bromide with phenobarbital, organophosphates, asparaginase, sulphonamides, zinc and clomipramine. Pancreatitis is rarely caused by infectious agents, Hill said.
Certain Dog Breeds at Higher Risk
In the United States, dog breeds appearing at highest risk for chronic pancreatitis are those classed by the American Kennel Club in the toy and non-sporting groups, according to Penny Watson, MA, VMD, writing in January’s Journal of Small Animal Practice. In the United Kingdom, terriers appear to be at increased risk for acute disease, while Cavalier King Charles spaniels, boxers, cocker spaniels and border collies are prone to chronic disease, she wrote.
Pancreatitis is a recognized complication of canine babesiosis, possibly due to hemolysis, Dr. Watson noted. In English cocker spaniels, chronic pancreatitis shows similarities to human type I autoimmune chronic pancreatitis, she added.
Hill said both acute and chronic pancreatitis are relatively commonly diagnosed in cats.
“Cats with pancreatitis commonly have co-morbidities, with inflammatory bowel disease and inflammatory liver disease being the most common,” he said. “This combination of pancreatitis, IBD and ILD is called ‘triaditis’ in cats.”
Hill said a clinical diagnosis of pancreatitis is determined by putting together the puzzle pieces: an appropriate patient history, compatible clinical signs, ruling out other disease processes, a positive pancreatic lipase immunoreactivity test and “typical” ultrasound findings.
Oklahoma State’s Dr. Hanzlicek said, “There is no question that the PLI is a very useful test for pancreatitis. No test is perfect, and this is also true for abdominal ultrasound. In some cases, these tests complement each other.”
In some instances, a practitioner without ultrasound access or competency could be at a disadvantage, he said.
First described for pancreatitis diagnosis in the mid-1980s, ultrasound technology and expertise of veterinary radiologists have improved, according to Steiner’s article on Texas A&M’s website. Hallmark changes attributable to pancreatitis include pancreatic enlargement, changes in echogenicity of the pancreas and of peripancreatic fat, fluid accumulation around the pancreas, a mass effect in the area, a dilated pancreatic duct and a swollen major duodenal papilla.
While the symptoms of pancreatitis may mimic other kinds of gastroenteritis, getting the diagnosis right can affect the patient’s treatment plan.
“The treatments are similar, but there are important differences,” Hanzlicek said. “In mild cases, treating one (disease) as the other, or vice versa, is probably fine. In more severely affected dogs or cats, early aggressive disease-specific treatment is ideal. In that situation, a definitive diagnosis is important.
“It’s always somewhat of a clinical judgment on the part of the veterinarian to decide between symptomatic empiric treatment or advanced diagnostics to pursue a more definitive treatment.
“Conditions such as acute gastroenteritis and acute pancreatitis are treated similarly with supportive and symptomatic care, while many other causes of acute vomiting have specific treatments, so it is important to have an accurate diagnosis,” Hill said.
“Metabolic and endocrine disorders, such as diabetic ketoacidosis, Addison’s disease and renal failure, can also have similar presentations, but can usually be ruled out with simple blood tests.”