Pancreatitis
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Pancreatitis
Acute pancreatitis is recognized commonly. Predisposing causes in dogs include hyperlipidemia, fatty meals, or obesity. Pancreatitis can occur in any dog, but middle-aged obese female dogs, schnauzers, and Yorkshire terriers seem to be most commonly affected. Vomiting may or may not be associated with eating, abdominal pain, fasting hyperlipidemia, bloody diarrhea, and rarely, diffuse subcutaneous fat necrosis. On radiographic examination, a mass or indistinctness (as the result of localized peritonitis) may be visible in the cranial right abdominal quadrant. Serum amylase and lipase activities can be measured, but false-negative and false-positive results are common, necessitating reliance on other findings. Leukocytosis with or without a left shift and with or without WBC toxicity (as the result of the sterile inflammation) and increased ALT and SAP concentrations (as the result of the proximity of the pancreas to the liver and obstruction of the biliary duct) are common. The latter occasionally causes extrahepatic biliary tract obstruction and subsequent icterus. Mild to moderate hypocalcemia may occur. Abdominal ultrasonography seems to be an excellent test for canine pancreatitis, and it usually reveals abnormalities in the pancreatic region. If a pancreatic mass is discovered during surgery, it must be biopsied; this is because chronic pancreatitis is grossly indistinguishable from pancreatic neoplasia, and both may be associated with normal or increased serum amylase and lipase values. Recently an assay for immunoreactive canine pancreatic lipase has been developed and validated (GI Laboratory at Texas A&M University); this test seems to hold promise for being a sensitive, specific test for acute pancreatitis.
Once considered rare in cats, pancreatitis is being recognized with increasing frequency in cats. Feline pancreatitis is more difficult to diagnose. Chronic pancreatitis is not uncommon in older cats, occurring in conjunction with cholangiohepatitis and sometimes with inflammatory bowel disease. The presence of the three diseases together has been referred to as “triaditis syndrome.” Vomiting is not as prominent as in dogs. Amylase and lipase values are usually in the normal reference range; feline trypsin-like immunoreactivity (fTLI) concentrations are increased in some patients. Abdominal ultrasonography may be useful if an obvious abnormality is found, but the sensitivity of ultrasonography is uncertain. A pancreatic biopsy may be required for a definitive diagnosis. Feline pancreatitis occasionally is due to toxoplasmosis or to feline infectious peritonitis (FIP) (see Chapter 15).
Gastritis, Enteritis, and Colitis
Chronic enteritis, colitis, or gastritis can cause various degrees of vomiting and may require mucosal biopsy for diagnosis. Abdominal imaging may delineate infiltrative or inflammatory intestinal patterns. If gastritis or enteritis is suspected or if the other major causes of chronic vomiting have been ruled out, gastric and intestinal mucosal biopsies via endoscopy or laparotomy are indicated. Inflammatory bowel disease is a significant cause of feline chronic vomiting. Duodenitis is also a significant cause of vomiting without diarrhea in dogs; therefore, both gastric and intestinal biopsies should be performed. Finally, because 10% to 20% of patients with colitis vomit, it is useful to perform endoscopy routinely on both the upper and lower intestinal tracts in patients (especially cats) with chronic vomiting. It is critical that mucosal tissue samples be taken and handled properly to avoid artifacts, which can render them nondiagnostic.
Hematemesis
Hematemesis is the vomiting of blood. It suggests gastric ulceration. The character of the vomitus may be either bright-red blood or digested blood that resembles coffee grounds. Administration of nonsteroidal anti-inflammatory drugs (especially concurrently with corticosteroids) is a major reason for canine ulceration. Renal and hepatic failure, mast cell tumor, shock with poor mucosal perfusion, and coagulopathy must be considered. After these have been ruled out, endoscopy is indicated and allows diagnosis of ulceration (especially because of a foreign object, inflammatory disease, or neoplasia). Alternatively, one may treat symptomatically for ulceration; however, such treatment may allow progression of underlying disease.
Abdominal Inflammation
Septic or nonseptic peritonitis (or inflammation of any abdominal organ) may cause vomiting. Abdominocentesis or abdominal lavage (see Chapter 10) may be needed, especially if physical examination or abdominal imaging suggests abdominal fluid. Occult cases may require exploratory surgery for diagnosis.
Gastrinoma
Gastrinoma (e.g., Zollinger-Ellison syndrome) is a gastrin-secreting tumor of the pancreatic islet cells; it increases gastric acid production and produces duodenal ulceration. Gastrinoma is rare but has been diagnosed more commonly since the advent of reliable serum gastrin assays. No other typical, unique clinicopathologic tests exist that suggest this disease. Any chronically vomiting middle-aged or older dog with weight loss or diarrhea is a reasonable suspect. Duodenal ulceration and reflux esophagitis are common. Resting gastrin concentrations are usually increased, but in rare cases one must measure gastrin concentrations after administering food or secretin.
AMYLASE
Controversial Indications
Patients (especially obese) with vomiting, abdominal pain, nonseptic inflammatory abdominal exudate, icterus, or a prior history of pancreatitis.
Disadvantages
Poor sensitivity and poor specificity. Serum amylase activity does not correlate with the severity of pancreatitis.
Analysis
Measured in serum, heparinized plasma, or body fluid by spectrophotometric methods via amyloclastic, saccharogenic, and chromogenic techniques. Turbidimetric, nephelometric, and “dry reagent” methods may also be used.
NOTE:
Different methods can give substantially different values. Some saccharogenic methods are affected by normal canine serum maltase concentrations and should not be used in dogs. Serum amylase activity is stable at room temperature for up to 7 days and at 4°C for as long as 1 month.
Normal Values
As with other enzymes, these vary among laboratories, depending on the technique and units used.
Danger Values
None.
Artifacts
See Introduction to Serum Chemistries.
Drug Therapy That May Cause Hyperamylasemia
Some drugs may occasionally cause pancreatitis (Table 9-3 ). Corticosteroids do not reliably increase serum amylase concentrations.
TABLE 9-3
Drugs That May Cause Acute Pancreatitis
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NOTE: These drugs do not reliably cause pancreatitis, and a history of administration of one of these drugs plus signs of pancreatitis cannot be assumed to be cause and effect. A patient with acute pancreatitis that is receiving one of these drugs, however, should undergo drug withdrawal, if possible.
Causes of Hypoamylasemia
Insignificant. This finding does not support a diagnosis of pancreatic insufficiency.
Causes of Hyperamylasemia
Decreased glomerular filtration (i.e., azotemia) and pancreatitis are two causes. Hyperamylasemia as the result of renal dysfunction usually is less than two to three times the upper limit of normal. Patients with pancreatitis may have normal to markedly increased values. Intestinal disease, ruptured intestines, and hepatic disease have been suspected of causing increased serum amylase because of amylase present in these tissues. Serum amylase level is an unreliable indicator of pancreatitis in cats. Hyperamylasemia in a vomiting or anorexic animal is an indication to search for pancreatitis by CBC, serum chemistry profile (including ALT and SAP), abdominal imaging, serum trypsin-like immunoreactivity (TLI), or a combination thereof.
Causes of Increased Fluid Amylase
When abdominal fluid amylase is greater than serum amylase, a nonseptic exudate caused by pancreatic disease is possible. Bowel rupture may also be possible.
LIPASE
Controversial Indications
Same as for amylase.
Disadvantages
Questionable sensitivity and specificity; some dogs with duodenal foreign objects, chronic gastritis, and abdominal carcinomas have very increased serum lipase activity without evidence of pancreatitis. Serum lipase activity does not correlate with the severity of pancreatitis.
Analysis
Measured in serum or body fluids via dry reagent analysis. Turbidimetric and titrimetric techniques are rarely used.
Normal Values
As for other enzymes, these vary from laboratory to laboratory, depending on the technique and units used.
Danger Values
None.
Artifacts
See Introduction to Serum Chemistries.
Drug Therapy That May Cause Hyperlipasemia
Same as for amylase (see Table 9-3) plus heparin. Corticosteroids (dexamethasone) may increase serum lipase activity up to fivefold over baseline without histologic evidence of acute pancreatitis; however, the lipase activity is usually only slightly greater than the reference range.
Causes of Hypolipasemia
Not significant. This finding does not support a diagnosis of pancreatic insufficiency.
Causes of Hyperlipasemia
These are similar to the causes of hyperamylasemia. Renal dysfunction increases serum lipase, usually less than two to three times normal, although it may rarely be more than four times normal. Not all patients with acute pancreatitis have increased serum lipase, and the increase in serum lipase activity is not proportional to the severity of the pancreatitis. Extremely increased lipase values have been associated with pancreatic carcinomas. Abdominal ultrasonography and increases in serum fTLI appear to be more useful than serum amylase or lipase in the diagnosis of feline pancreatitis. In addition to serum TLI, trypsin-activating peptide (TAP) and phospholipase A2 have been investigated as tests for pancreatitis in dogs; however, none have become accepted as valued clinical tests.
CANINE IMMUNOREACTIVE PANCREATIC LIPASE
Common Indications
Patients (especially obese) with vomiting, abdominal pain, nonseptic inflammatory abdominal exudate, icterus, or a prior history of pancreatitis.
Advantages
Appears to be sensitive and specific and only requires a serum sample.
Disadvantages
Currently the only laboratory offering this test for dogs is GI Laboratory, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4474.
Analysis
Measured in serum by enzyme-linked immunosorbent assay (ELISA). See Appendix I for availability.
Normal Values
2.2 to 102.1 μg/L.
Artifacts
Uncertain.
Causes of Decreased Values
Exocrine pancreatic insufficiency (EPI) or isolated pancreatic lipase deficiency. However, slightly more overlap exists between normal dogs and dogs with EPI than for serum TLI concentration. Thus serum TLI remains the test of choice for EPI.
Causes of Increased Values
Pancreatic inflammation is currently the only recognized cause of an increase. Further experience with this test may change the indications and interpretation of this test.
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