A Review for Vet Students - If you’ve spent any time working in a small animal practice, you have probably treated a dog (or seen a dog treated) for “pancreatitis.”
Did the dog actually have pancreatitis, though? It turns out Diagnosing Acute Pancreatitis in Dogs is not that simple.
The pathophysiology of pancreatitis is not fully understood. Pancreatitis is currently attributed to the premature activation of zymogens within the pancreas. Under normal circumstances, zymogens are stored in the pancreas in an inactive form; they are are activated once they are excreted and reach the duodenum. When zymogens are activated within the pancreas, however, they can have a number of harmful effects, including pancreatic autodigestion, inflammation, and free radical production.
Pancreatitis is often idiopathic in nature. Some cases have predisposing risk factors, such as dietary indiscretion, hyperlipidemia, obesity, biliary disease, inflammatory bowel disease, or genetic predisposition (in Miniature Schnauzers).(1) In many cases, however, no predisposing factors can be identified and there is no clear explanation for why the pet developed pancreatitis.
When a pet presents with an acute onset of vomiting and diarrhea, the first step is typically to perform a CBC and serum biochemistry. Typical findings in a dog with pancreatitis include red blood cell count changes (anemia or polycythemia), neutrophilia, thrombocytopenia, hypoalbuminemia, hypocalcemia, and elevated liver values. Amylase and lipase may or may not be elevated; these tests lack sensitivity and specificity, so they cannot be relied upon to diagnose or rule out pancreatitis.
In many practices, the in-house IDEXX SNAP® cPL test is used as an aid in the diagnosis of pancreatitis. This test, however, also has significant limitations. In one study of dogs presenting for acute gastrointestinal signs and abdominal disease, the SNAP® cPL was determined to have a sensitivity of 82% and a specificity of only 59%.(2) This means that if you rely upon the SNAP® cPL test alone to diagnose pancreatitis, you will miss nearly 20% of cases and over 40% of the dogs you diagnose with pancreatitis will be misdiagnosed!
Another commonly utilized test is the Spec cPL, which is performed by reference laboratories. In the study reported above, the Spec cPL was found to have a higher specificity than the SNAP® cPL, with a specificity of 77%, but a slightly lower sensitivity at 66%.(2) These numbers illustrate that the Spec CPL also has significant limitations in diagnosing pancreatitis. Combining these two tests can give a better picture of a pet’s true diagnosis, but it’s still difficult to make a diagnosis based solely on the results of laboratory testing.
Radiographs can have significant value in working up a case of suspected pancreatitis. The primarily role of radiographs lies in ruling out other causes of a dog’s gastrointestinal signs. In some cases, characteristic findings such as decreased abdominal detail or a mass effect in the right cranial abdomen may be observed, but abdominal radiographs are often normal in dogs with pancreatitis.
Abdominal ultrasound can also be beneficial in determining whether a dog has pancreatitis. Characteristic findings of acute pancreatitis on abdominal ultrasound include the presence of an enlarged pancreas, surrounded by fluid, with a heterogenous or hypoechoic appearance. A hypoechoic pancreas with hyperechoic peripancreatic fat may also be observed, especially in the presence of hepatic necrosis.
Although it is rarely performed, histopathology is considered the most accurate method of diagnosing pancreatitis. Biopsies may be taken surgically or laparoscopically, although either method carries the risk of contributing to worsening pancreatitis.
Even histopathology, however, is not 100% sensitive! Recent studies have found that a lack of inflammation on a given biopsy sample does not rule out pancreatitis, because there may be focal inflammation in other areas of the pancreas.(3)
In reality, diagnosing pancreatitis relies on the simultaneous interpretation of a variety of diagnostics… and requires you to become comfortable with a little bit of uncertainty!
In most cases, a diagnosis of pancreatitis is made based upon the following:
Fortunately, the treatment for pancreatitis is supportive in nature. As long as other serious conditions (foreign bodies, metabolic disease, etc.) are ruled out with blood tests and radiographs, supportive measures such as IV fluids, pain medications, and antiemetics will be beneficial for most patients with acute abdominal signs.
Still, it is important to understand the limitations of common diagnostic tests, so that you can think through these cases more effectively. Remember, an elevated amylase/lipase or a positive IDEXX SNAP® cPL does not always mean pancreatitis!
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