According to the American College of Gastroenterology's guidelines, there are three criteria that must be present to diagnose acute pancreatitis, including:
- Severe abdominal pain
- Amylase or lipase levels that are three times higher than the upper limit of normal
- "Characteristic" abdominal imaging results
Chronic pancreatitis may also be diagnosed using these tests as well as others.
More about the tests used for both types of pancreatitis:
- Amylase is the pancreatic and salivary gland enzyme responsible for digesting carbohydrates. The level will increase 2 to 12 hours after the beginning of symptoms of acute pancreatitis and peaks at 12 to 72 hours afterward. It may rise 5 to 10 times the normal level and will usually return to normal within a week. Pancreatitis is likely if the level reaches 3 times above the upper limit of normal. Amylase also may be monitored in people with chronic pancreatitis; it will often be moderately elevated until the cells that produce it are destroyed (as a result of the pancreatitis), at which point blood levels of amylase may be decreased. It should be noted that amylase is an enzyme that has different forms called isoenzymes: P-amylase refers to the form made by the pancreas and S-amylase refers to the form made by the salivary glands. Normally, a total amylase test is requested. Sometimes, the isoenzyme tests are requested individually to distinguish pancreatic and non-pancreatic causes of increased amylase.
- Lipase is the pancreatic enzyme that, along with bile from the liver, digests fats. It is another test commonly used to diangose pancreatitis. Its level increases in the blood within 4 to 8 hours of the beginning of an acute attack and peaks at 24 hours afterward. Lipase is both more sensitive and more specific than amylase for the diagnosis of acute pancreatitis. However, there are other sources of lipase in the digestive tract. In some assays that detect non-pancreatic lipase, milder elevations may occur as a result of non-pancreatic disorders. In people with pancreatitis, lipase may rise to several times its normal level and remain elevated longer than amylase. Like with the amylase test, pancreatitis is diagnosed if the lipase level reaches 3 times above the upper limit of normal. As cells are destroyed with chronic pancreatitis and as lipase production drops to less than 10% of the normal level, steatorrhea (fatty, foul-smelling stools) will form. As chronic pancreatitis progresses, amylase and lipase may be normal or decreased, even during acute attacks.
- Trypsin is the pancreatic enzyme that digests proteins. Measurement of serum trypsin is thought to be the most sensitive blood test for pancreatitis, particularly chronic pancreatitis, but is not widely available and is not routinely used. The available test is variably identified as trypsinogen, trypsin-like immunoreactivity, or immunoreactive trypsin.
Tests that may be used to check for complications of acute pancreatitis include:
- Complete blood count (including white blood cell count)
- Comprehensive metabolic panel (including bilirubin, liver enzymes)
- C-reactive protein (a measure of inflammation)
Other tests that may be used to help diagnose and evaluate chronic pancreatitis include:
- Fecal fat
- Fecal pancreatic elastase
- Sweat (chloride) test for diagnosis of cystic fibrosis
- Molecular biology tests for genetic mutations such as those associated with cystic fibrosis
Non-laboratory tests used to diagnose pancreatitis may include:
- Abdominal ultrasound
- Endoscopic retrograde cholangiopancreatography (ERCP): a test that uses a flexible scope inserted through the mouth and threaded through the esophagus to see and document damage to the pancreas and/or bile ducts
- Magnetic resonance cholangiopancreatography (MRCP): a type of magnetic resonance imaging (MRI) used to image the pancreas and bile ducts; often used before or instead of ERCP because it is faster and non-invasive; also useful in distinguiding pancreatitis from pancreatic cancer
- Computed tomography (CT) scan
- Secretin testing (not widely available) in which a tube is positioned in the duodenum to collect pancreatic secretions stimulated by intravenous (IV) administration of secretin. Secretin is a hormone that causes the pancreas to release fluid containing digestive enzymes. The amount of enzymes, such as lipase and trypsin, and bicarbonate in the pancreatic secretion is measured and compared to normal values.
For more information on imaging studies, visit RadiologyInfo.org.