How do I diagnose and initially manage acute pancreatitis?

Diagnosis and Initial Management of Acute Pancreatitis

Diagnose acute pancreatitis when any two of the following three criteria are present: characteristic epigastric abdominal pain radiating to the back, serum lipase ≥3 times the upper limit of normal, or imaging findings consistent with pancreatitis on contrast-enhanced CT or MRI. 1, 2

Diagnostic Testing

Biochemical Confirmation

• Serum lipase is the preferred first-line test over amylase because of higher specificity, longer diagnostic window (remains elevated longer), and superior performance in alcohol-induced pancreatitis and delayed presentations. 1, 2, 3
• A diagnostic threshold of ≥3 times the upper limit of normal is required for lipase to confirm the diagnosis. 1, 2
• If lipase is unavailable, serum amylase may be used, but requires a higher threshold of ≥4 times the upper limit of normal due to lower specificity. 4, 1
• Critical pitfall: Enzyme elevations <3 times the upper limit of normal have low specificity and should not be considered diagnostic on their own. 1
• The magnitude of enzyme elevation does not correlate with disease severity—patients can have severe pancreatitis with modest enzyme rises, and vice versa. 1, 2
• Daily measurement of pancreatic enzymes provides no useful information for monitoring progress and should be avoided. 1, 2

Etiologic Work-up (Obtain at Admission)

• Liver chemistries (bilirubin, AST, ALT, alkaline phosphatase) to assess for gallstone-related pancreatitis—early elevation suggests biliary etiology. 1, 2
• Serum triglycerides: levels >1000 mg/dL indicate hypertriglyceridemia-induced pancreatitis. 1, 2
• Serum calcium to identify hypercalcemia as a precipitating factor. 1, 2

Imaging Strategy

• Abdominal ultrasound should be performed in all patients at admission to detect gallstones, bile duct dilation, and free peritoneal fluid—essential for deciding whether urgent ERCP is needed. 1, 2, 3

• However, the pancreas is poorly visualized in approximately 25-50% of ultrasound examinations, limiting its ability to exclude pancreatitis. 1, 3

• Chest and abdominal X-rays should be obtained routinely to exclude alternative life-threatening conditions such as perforated viscus, intestinal obstruction, or leaking abdominal aortic aneurysm. 4, 1, 2

• Contrast-enhanced CT is NOT routinely indicated in the first 72 hours unless there is genuine diagnostic uncertainty after clinical and biochemical assessment. 1, 2

• When CT is indicated, perform it 72-96 hours after symptom onset to avoid underestimating pancreatic necrosis—sensitivity for detecting necrosis approaches 100% at this interval. 1, 2

• Specific indications for contrast-enhanced CT include:

  • Predicted severe disease (APACHE II score >8)
  • Evidence of organ failure within the first 72 hours
  • C-reactive protein >150 mg/L at 48 hours
  • Persistent diagnostic uncertainty
  • Signs of sepsis or clinical deterioration 6-10 days after admission 1, 2

Severity Assessment (Perform Within First 48 Hours)

Immediate Assessment (At Presentation)

• APACHE II score ≥8 predicts severe acute pancreatitis and should be calculated on admission and repeated to capture worst values in the first 24 hours. 4, 1, 2
• Document the presence of organ failure (respiratory, circulatory, or renal)—this defines a severe attack. 4, 1, 2
• Assess body mass index (BMI >30 is a risk factor), pleural effusion on chest X-ray, and cardiovascular/respiratory/renal compromise. 4

At 48 Hours After Admission

• C-reactive protein >150 mg/L at 48 hours is the most reliable laboratory marker for severe disease. 4, 1, 2, 3
• Glasgow score ≥3 or persistent organ failure after 48 hours also indicates severe disease. 2
• Procalcitonin is the most sensitive test for detecting pancreatic infection—low procalcitonin values strongly predict the absence of infected necrosis. 1, 2

Initial Management

Fundamental Medical Treatment (Start Immediately)

• Aggressive intravenous fluid resuscitation to correct the major fluid deficit that occurs early in acute pancreatitis—modern aggressive fluid replacement has reduced early-phase deaths. 4
• Pain control with intravenous opiates (safe if used judiciously). 5
• Bowel rest initially, but advance to oral diet as tolerated in mild cases. 2
• Close monitoring of vital signs, hematocrit, blood urea nitrogen, and creatinine. 2

Management by Severity

Mild Acute Pancreatitis:

• Advance to regular oral diet as tolerated
• Oral analgesics for pain control
• Routine vital-sign monitoring 2

Moderately Severe Acute Pancreatitis:

• Initiate enteral nutrition (oral, nasogastric, or naso-enteric); if not tolerated, use parenteral nutrition
• Intravenous analgesia
• Intravenous fluid resuscitation
• Monitor hematocrit, blood urea nitrogen, and creatinine
• Continuous vital-sign monitoring 2

Severe Acute Pancreatitis:

• Prefer early enteral nutrition over parenteral nutrition—enteral feeding is associated with lower rates of death, multiorgan failure, local complications, and systemic infections. 2, 6
• Intravenous analgesia
• Early aggressive fluid resuscitation
• Mechanical ventilation when indicated
• Admit to intensive care unit whenever possible 2

Antibiotic Therapy

• Routine prophylactic antibiotics are NOT recommended—they do not significantly reduce mortality or morbidity. 2
• Antibiotics are indicated only for infected necrotizing pancreatitis or when infection is suspected based on elevated procalcitonin or positive fine-needle aspiration. 2
• In severe cases with >30% necrosis and confirmed infection, empiric therapy with imipenem/cilastatin, meropenem, or doripenem (extended infusion) is recommended. 2, 6

Endoscopic Intervention

• Urgent therapeutic ERCP should be performed as soon as possible in patients with biliary pancreatitis and common bile duct obstruction or acute cholangitis. 2

Special Situations and Follow-up

• In patients >40 years with unexplained pancreatitis, perform CT or endoscopic ultrasound (EUS) to exclude underlying pancreatic malignancy, even after a single episode. 1, 2
• EUS is the preferred test for idiopathic pancreatitis when performed 2-6 weeks after resolution—it identifies an etiology in 29-88% of cases. 1, 2
• Before labeling pancreatitis as "idiopathic," obtain at least two high-quality abdominal ultrasounds to search for occult gallstones. 2
• The correct diagnosis should be established within 48 hours of admission to avoid missing alternative life-threatening intra-abdominal catastrophes. 1