Diagnosis of Acute Pancreatitis

Laboratory Studies in Acute Pancreatitis

1. Serum Pancreatic Enzymes

• Lipase: Elevated ≥ 3× ULN is highly indicative of acute pancreatitis (more sensitive and specific than amylase).
• Amylase: Elevated ≥ 3× ULN but less reliable compared to lipase.

2. Complete Blood Count (CBC)

• Hematocrit (Hct):
  • Elevated Hct indicates hemoconcentration, guiding IV fluid therapy to normalize levels.
  • Persistently high Hct may suggest third-spacing and inadequate fluid resuscitation.
  • Sudden Hct drop may indicate rare pancreatic hemorrhage.
• White Blood Cell (WBC) Count:
  • Elevated WBCs early in pancreatitis suggest severity.
  • Worsening leukocytosis during serial evaluation is a marker for infected necrosis.

3. Basic Metabolic Panel (BMP)

• Volume and Perfusion Markers:
  • Elevated blood urea nitrogen (BUN), creatinine, and lactate levels indicate volume depletion and tissue hypoperfusion.
• Blood Glucose: Elevated levels due to impaired insulin secretion.
• Calcium:
  • Hypocalcemia: Indicates fatty acid saponification (a hallmark of severe pancreatitis).
  • Hypercalcemia: May be a cause of acute pancreatitis.

4. Inflammatory Markers

• C-Reactive Protein (CRP): Levels > 150 mg/L after 3 days suggest severe or necrotizing pancreatitis.
• Procalcitonin: Elevated levels are sensitive for infected necrosis.
• Interleukin-6 (IL-6): A marker for infected necrosis and remote organ failure.

5. Liver Chemistries

• Indicative of biliary pancreatitis:
  • Aminotransferases: ALT > 150 U/L, AST > 3× ULN.
  • Cholestasis Markers: Increased bilirubin, alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT).

6. Lactate Dehydrogenase (LDH)

• Elevated levels suggest severity and necrotizing pancreatitis.

7. Serum Triglycerides

• Levels > 1,000 mg/dL indicate hypertriglyceridemia-induced pancreatitis.
• Prompt measurement is essential, as levels decrease rapidly with fasting.

Clinical Notes

• The degree of enzyme elevation (lipase/amylase) does not correlate with the severity or prognosis of pancreatitis.
• Determination of serum calcium is critical due to its dual role:
  • Hypercalcemia as a potential cause of pancreatitis.
  • Hypocalcemia resulting from the disease process itself.

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Imaging in Acute Pancreatitis

1. Ultrasound Abdomen

Indications: First-line imaging modality for all patients.

• Primarily used to identify biliary etiology (e.g., gallstones), as features of acute pancreatitis are visible in only ~20% of cases.

Findings:

1. Acute Pancreatitis (seen in some cases):
   • Enlarged, hypoechoic pancreas (indicating pancreatic edema).
   • Presence of peripancreatic fluid or ascites.
2. Biliary Pancreatitis:
   • Cholelithiasis and/or gallbladder sludge.
   • Dilated biliary tree.
3. Complications:
   • Pancreatic pseudocysts.
   • Walled-off necrosis (typically >4 weeks after symptom onset).

2. CT Abdomen and Pelvis with IV Contrast

Indications:

• Diagnostic uncertainty (e.g., atypical clinical features with mildly elevated pancreatic enzymes).
• Acute clinical deterioration or lack of improvement within 48–72 hours.
• Severe pancreatitis, particularly to assess for complications (best performed >5–7 days after symptom onset).
• Evaluation of underlying etiology when routine studies are inconclusive.

Findings:

1. Acute Pancreatitis:
   • Enlarged pancreatic parenchyma with edema.
   • Indistinct pancreatic margins and surrounding fat stranding.
   • Peripancreatic free fluid.
2. Complications:
   • Necrotizing Pancreatitis: Nonenhancing pancreatic tissue.
   • Acute Necrotic Collections: Ill-defined, heterogeneous collections with varying densities.
   • Walled-off Necrosis: Encapsulated necrotic material (develops >4 weeks after onset).
   • Infection: Presence of air within pancreatic or peripancreatic tissues.

Key Considerations

• Ultrasound is preferred initially to identify gallstones or biliary sludge as a cause of pancreatitis.
• CT is not routinely required for diagnosis but is essential in assessing complications or confirming severe necrotic pancreatitis.
• Optimal timing for contrast-enhanced CT is 5–7 days after symptom onset to allow clear differentiation between viable and necrotic tissue.
• In patients over 40 with idiopathic pancreatitis, consider the possibility of an underlying pancreatic tumor.

3. X-ray Chest and Abdomen

Indications: Not routinely indicated but may be performed as part of the initial workup in cases of undifferentiated abdominal pain.

Findings:

• Abdominal X-ray:
  • Sentinel Loop Sign: Dilatation of a small intestinal loop (typically the duodenum or jejunum) in the left upper abdomen.
  • Colon Cut-off Sign: Gaseous distention of the ascending and transverse colon, abruptly terminating at the splenic flexure.
  • Calcified Gallstones or Pancreatic Stones.
• Chest X-ray:
  • Pleural Effusion and Pulmonary Edema, indicating possible ARDS (acute respiratory distress syndrome).

4. MRI Abdomen

Indications:

• Used in conjunction with MRCP for suspected choledocholithiasis.
• An alternative to CT, especially in patients with contraindications to contrast or when detailed pancreatic imaging is needed.

Findings:

• Enlarged, Edematous Pancreas.
• Pancreatic Necrosis.
• Complications:
  • Walled-off necrosis.
  • Pseudocysts.

5. Magnetic Resonance Cholangiopancreatography (MRCP)

Indications:

• Performed prior to therapeutic ERCP in suspected biliary pancreatitis.

Findings:

• Choledocholithiasis (gallstones in the common bile duct).
• Identification of pancreatic ductal anomalies that may contribute to acute pancreatitis.
• Cholelithiasis and Choledocholithiasis.

6. Endoscopic Retrograde Cholangiopancreatography (ERCP)

Indications:

• Suspected choledocholithiasis when MRCP or MRI is not feasible.
• Evaluation for sphincter of Oddi dysfunction in patients with recurrent pancreatitis where other imaging (e.g., MRCP, EUS) is inconclusive.

7. Endoscopic Ultrasound (EUS)

Indications:

• Evaluation of the underlying cause when routine initial workup fails to establish the etiology.

Findings:

• Occult Microlithiasis (small gallstones).
• Pancreatic Neoplasms.
• Chronic Pancreatitis.
• Identification of other pancreatic parenchymal, ductal, and ampullary disorders.

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Severity Grading and Prognostic Scores for Acute Pancreatitis:

Severity grading and prognostic scores are critical for assessing the clinical course, predicting outcomes, and guiding treatment strategies in acute pancreatitis

1. Revised Atlanta Classification

• Purpose: Classifies the severity of pancreatitis based on organ failure and complications.
• Severity Classification:
  • Mild: No organ failure, no local or systemic complications.
  • Moderately Severe: Transient organ failure (<48 hours) and/or local or systemic complications.
  • Severe: Persistent organ failure (>48 hours).
  • Note: Organ failure is assessed using the modified Marshall scoring system.

2. CT Severity Index (CTSI) and Modified CTSI (MCTSI) for Acute Pancreatitis

CT Severity Index (CTSI)

• Purpose: Estimates the severity, morbidity, and mortality of acute pancreatitis based on CT findings, particularly the extent of pancreatic inflammation and necrosis. It is ideally performed 72 hours or later after symptom onset.
• Components:
  • Degree of Pancreatic Inflammation
  • Degree of Parenchymal Necrosis

Modified CT Severity Index (MCTSI)

• Purpose: A modified version of the CTSI, this index adds extrapancreatic complications as a factor to provide a more comprehensive severity assessment. It helps evaluate the extent of systemic involvement.
• Components:
  • Degree of Pancreatic Inflammation
  • Degree of Parenchymal Necrosis
  • Presence of Extrapancreatic Complications

Comparison Table:

Parameter	CTSI	MCTSI
Degree of Inflammation	– Normal pancreas: 0 – Localized or diffuse enlargement: 1 – Peripancreatic inflammation: 2	– Normal pancreas: 0 – Localized or diffuse enlargement: 2 – Peripancreatic inflammation: 2
Parenchymal Necrosis	– None: 0 – < 30% necrosis: 2 – 30–50% necrosis: 4 – > 50% necrosis: 6	– None: 0 – < 30% necrosis: 2 – 30–50% necrosis: 4 – > 50% necrosis: 6
Extrapancreatic Complications	Not included.	Adds 2 points for extrapancreatic complications (e.g., pleural effusion, ascites, or organ failure).
Severity Classification	– Mild: 0–3 points – Moderate: 4–6 points – Severe: 7–10 points	– Mild: 0–2 points – Moderate: 4–6 points – Severe: 8–12 points
Clinical Utility	Focuses on pancreatic inflammation, necrosis, and fluid collections.	Incorporates both pancreatic and extrapancreatic complications for a more comprehensive severity assessment.

Summary of Key Differences Between CTSI and MCTSI:

1. CTSI focuses solely on pancreatic inflammation and necrosis, offering a simpler, straightforward score based on the pancreatic region affected.
2. MCTSI introduces an additional component for extrapancreatic complications, which helps assess the impact of the disease beyond the pancreas itself, providing a more holistic view of severity.
   • Both systems are widely used and have similar prognostic capabilities, but MCTSI may be more comprehensive, especially when evaluating systemic complications of acute pancreatitis.

Clinical Application:

• CTSI is generally more useful for immediate assessment of pancreatic changes on imaging.
• MCTSI can be more beneficial for long-term monitoring and evaluating extrapancreatic consequences, especially in severe cases with associated complications.

3. Ranson Criteria for Acute Pancreatitis

• Purpose: Used to assess the severity and prognosis of biliary and nonbiliary pancreatitis. Full assessment occurs after 48 hours.
• Scoring: Each parameter is worth 1 point. A composite score of ≥ 3 points indicates a high risk for severe pancreatitis.

On Admission:

Parameter	Nonbiliary Pancreatitis	Biliary Pancreatitis
Age	> 55 years	> 70 years
White Blood Cell Count (WBC)	> 16,000/mm³	> 18,000/mm³
Blood Glucose	> 200 mg/dL	> 220 mg/dL
Serum LDH	> 350 U/L	> 400 U/L
Serum AST	> 250 U/L	> 250 U/L

After 48 Hours:

Parameter	Nonbiliary Pancreatitis	Biliary Pancreatitis
Hematocrit (Hct) decrease	> 10%	> 10%
Blood Urea Nitrogen (BUN) increase	> 5 mg/dL	> 2 mg/dL
Serum Calcium	< 8 mg/dL	< 8 mg/dL
Arterial pO2	< 60 mm Hg	N/A
Fluid Sequestration	> 6 L	> 4 L
Serum Base Deficit	> 4 mmol/L	> 5 mmol/L

• Interpretation: A score ≥ 3 points indicates a high risk for severe acute pancreatitis.

4. APACHE II Score

• Purpose: Primarily used in the ICU setting to assess the severity of acute pancreatitis.
• Interpretation: APACHE II score ≥ 8 indicates severe pancreatitis with a guarded prognosis.

5. BISAP Score (Bedside Index of Severity of Acute Pancreatitis)

• Purpose: Estimates in-hospital mortality due to acute pancreatitis.
• Scoring: Each criterion is worth 1 point. A BISAP score ≥ 2 indicates severe pancreatitis.

Criterion	Score
BUN > 8.9 mmol/L	1
Altered mental status	1
Presence of SIRS (Systemic Inflammatory Response Syndrome)	1
Age > 60 years	1
Pleural effusion on chest x-ray	1