CT Grading of Acute Pancreatitis: Balthazar CT Severity Index
The Balthazar CT Severity Index is the recommended grading system for acute pancreatitis, combining CT grade (0-4 points) with extent of pancreatic necrosis (0-6 points) to yield a total score of 0-10 that directly predicts complications and mortality. 1
The Balthazar CT Severity Index Components
CT Grade (0-4 points):
- Grade A (0 points): Normal pancreas
- Grade B (1 point): Edematous pancreatitis
- Grade C (2 points): Grade B plus mild extrapancreatic changes
- Grade D (3 points): Severe extrapancreatic changes including one fluid collection
- Grade E (4 points): Multiple or extensive extrapancreatic collections 1
Necrosis Score (0-6 points):
- None: 0 points
- Less than one-third: 2 points
- One-third to one-half: 4 points
- Greater than one-half: 6 points 1
Total CT Severity Index = CT Grade + Necrosis Score (0-10)
Prognostic Correlation with Outcomes
The index directly correlates with morbidity and mortality:
Complications:
- Score 0-3: 8% complication rate
- Score 4-6: 35% complication rate
- Score 7-10: 92% complication rate
Mortality:
- Score 0-3: 3% mortality
- Score 4-6: 6% mortality
- Score 7-10: 17% mortality 1
Critical Timing Considerations
Do not perform CT before 72 hours of symptom onset unless a specific management decision requires it (such as determining need for intervention). Early CT significantly underestimates the extent of pancreatic necrosis because the full necrotic process takes at least 4 days to develop. 2, 1
When to Obtain CT:
- After 72 hours in patients with predicted severe disease (APACHE II score >8)
- After 72 hours in patients with evidence of organ failure during initial 72 hours
- Selectively based on clinical features in patients not meeting these criteria 2, 1
Proper CT Technique for Accurate Grading
Contrast-enhanced CT is mandatory for accurate assessment. Non-contrast CT provides suboptimal information and should be avoided when staging severity. 1
Technical Protocol:
- Spiral or multislice CT required
- 500 ml oral contrast via mouth or nasogastric tube
- Initial non-contrast scan to identify pancreatic levels
- Bolus IV contrast: 100 ml non-ionic contrast at 3 ml/s via power injector
- Pancreatic phase imaging: Thin collimation (≤5 mm) starting 40 seconds after injection
- Portal venous phase: Second series at 65 seconds for vascular patency assessment 1
Defining Necrosis on CT:
Non-opacification of at least one-third of the pancreas, or an area >3 cm diameter, indicates necrosis. 1
Follow-Up CT Strategy
CT Severity Index 0-2 (mild pancreatitis):
- Further CT only if clinical status changes suggesting new complication
CT Severity Index 3-10:
- Additional scans only if patient deteriorates or fails to show continued improvement
- Consider single scan before discharge in apparently uncomplicated recovery to detect asymptomatic complications (pseudocyst, arterial pseudoaneurysm) 1
Clinical Context and Pitfalls
The Balthazar score demonstrates superior accuracy for predicting overall acute pancreatitis severity and pancreatic necrosis compared to clinical scoring systems like APACHE II and Ranson criteria. 3 However, CT on admission solely for severity assessment is not recommended because its predictive accuracy is similar to clinical scoring systems, and early imaging underestimates disease severity. 4
Common pitfall: Ordering CT too early (<72 hours) leads to underestimation of necrosis and may result in inappropriate triage or treatment decisions. The exception is when immediate intervention is being considered based on clinical deterioration.
The index remains highly relevant in modern practice, with recent studies confirming its prognostic value when combined with laboratory markers for comprehensive risk stratification. 5