Tests
1st tests to order
serum lipase (or amylase if lipase is unavailable)
Test
Use serum lipase in preference to serum amylase, if available, due to its higher sensitivity and larger diagnostic window.[8][28][54] Amylase can be normal in patients with acute pancreatitis caused by long-term alcohol misuse; in these patients, serum lipase is more sensitive. Serum lipase is more sensitive than amylase in patients with lipemic serum (e.g., in hypertriglyceridemia-induced pancreatitis).
Serum lipase and/or amylase can be used to establish the diagnosis of acute pancreatitis when greater than 3 times normal in a patient with severe acute epigastric pain.[8]
Serum amylase levels usually peak at around 48 hours, and decrease to normal or near normal over the next 3-7 days. Serum lipase may remain elevated for up to 14 days.[28]
In patients with a slightly elevated lipase, the diagnosis of acute pancreatitis should be questioned.
Result
>3 times the upper limit of the normal range
liver function tests
Test
Elevation of aspartate aminotransferase/alanine aminotransferase (AST/ALT) is specific, but not sensitive, for gallstone pancreatitis. If alkaline phosphatase and bilirubin are raised, the possibility of a retained common bile duct stone (choledocholithiasis) must be considered.[57]
Result
elevated; if AST/ALT >3 times the upper normal limit, predicts gallstone disease as etiology in 95% of cases. Bilirubin rising or over 5 mg/dL in the setting of cholangitis (leukocytosis, fever, SIRS) signifies a need for early ERCP
CBC and differential
Test
Mild leukocytosis with left shift and elevated hematocrit as a result of dehydration or low hematocrit as a result of hemorrhage can be seen. The development of hemoconcentration is associated with an increased risk of developing necrotizing pancreatitis and organ failure.[56]
Result
leukocytosis
hematocrit
BUN and serum electrolytes
Test
Elevated levels suggest dehydration/hypovolemia and an increased risk for development of severe disease.[8] Serial measurements can aid monitoring of the patient's response to therapy; BUN should be repeated 6 hours after admission.[47] Elevated or rising BUN indicates reduced renal perfusion, and hence reduced pancreatic perfusion and a need for more aggressive hydration.[8][28]
Result
elevated in severe cases; BUN rising or over 20 mg/dL indicates reduced pancreatic perfusion (urea >20 mg/dL is an independent predictor of mortality), elevated creatinine (≥2 mg/dL) indicates the patient may develop severe disease with renal failure
arterial blood gas
Test
It is important to monitor the arterial oxygenation since patients may be hypoxemic, requiring supplemental oxygen. During the initial management, consider arterial blood gases every 12 hours for the first 3 days to assess both oxygenation and acid-base status.[5]
Result
hypoxemia and disturbances in acid-base balance
CRP
Test
Early and serial CRP testing is used in acute pancreatitis as an indicator of severity and progression of inflammation.[28][58]
The accuracy of CRP for the diagnosis of pancreatic necrosis in people with acute pancreatitis has not been reliably determined.[59]
Result
if >15 mg/dL, is associated with pancreatic necrosis (measured on day 3)
transabdominal ultrasound
Test
Not needed for diagnosis of acute pancreatitis, but should be performed in all patients following diagnosis to rule out gallstones.
Result
dilated common bile duct on US raises the suspicion of a retained stone
chest x-ray
Test
Radiographic studies are not used for diagnosis of acute pancreatitis, but may determine possible causative factors and exclude other diagnoses.
Result
may show atelectasis and pleural effusion (especially in the left side)
ratio of serum lipase:amylase
Test
Based on multiples of upper limit of normal. High ratio favors alcoholic pancreatitis.[68]
Result
>5
serum triglycerides
Test
Should be checked as part of investigation into causative factors.
Result
>1000 mg/dL and as high as 9000 mg/dL for true hypertriglyceridemia-induced acute pancreatitis (elevated levels of a few hundred mg/dL often seen in patients with acute pancreatitis due to other causes)
Tests to consider
abdominal CT scan
Test
CT scan of the abdomen is not needed in the majority of patients. CT is useful in patients in whom the diagnosis of acute pancreatitis is difficult to establish. American College of Gastroenterology guidelines recommend CT or MRI after 48 hours in patients who do not improve or whose symptoms worsen.[8] Other guidelines recommend a delay of 72–96 hours after symptom onset before contrast-enhanced CT or MRI to assess for necrosis.[28][47] Do not order unenhanced CT alongside intravenous contrast-enhanced CT because the addition of unenhanced CT does not provide additional diagnostic information and exposes patients to unnecessary radiation.[61][62]
Result
CT with intravenous contrast later in the the disease course may show nonenhancing regions indicating the presence of necrosis, or pseudocysts (after approximately 4 weeks)
magnetic resonance imaging/magnetic resonance cholangiopancreatography (MRI/MRCP)
Test
Preferred to ERCP for the evaluation of the CBD in low risk patients when a retained CBD stone is suspected. MRI employing MRCP has the advantage of not requiring intravenous contrast or radiation, although intravenous gadolinium enhances images as compared with noncontrast MRI.
In addition, MRCP allows better visualization of common bile duct stones and the pancreatic duct compared to CT. It can more readily distinguish solid from cystic in dealing with peripancreatic collections.[62]
Result
findings may include stones, tumors, diffuse or segmental enlargement of the pancreas with irregular contour and obliteration of the peripancreatic fat, necrosis, or pseudocysts
endoscopic ultrasound (EUS)
Test
EUS can be useful as an alternative to MRCP to identify choledocholithiasis and tumors.[8] EUS also allows fine needle aspiration of tumors for diagnosis.
Result
findings may include stones, biliary sludge, pancreatic divisum, and other abnormalities of the pancreatobiliary ducts
Emerging tests
procalcitonin
Test
Procalcitonin appears to be sensitive for detection of pancreatic infection, with low serum levels a strong negative predictor of infected necrosis.[66] Its use is supported by some international guidelines.[28]
Result
elevated; normal levels make the diagnosis of infected pancreatic necrosis unlikely
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