5-variable severity score for acute pancreatitis (AUC 0.82). Assessed within 24h of admission — no 48h wait required. Score ≥ 3 = ICU-level care.
Within 24 Hours of Presentation
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Rapid severity assessment of acute pancreatitis within 24 hours of presentation.
Single time-point assessment — overcomes the 48h limitation of Ranson Criteria.
Identifying patients at high risk for organ failure and in-hospital mortality.
Guides triage decisions regarding ICU admission for acute pancreatitis.
Advantage Over Ranson
BISAP requires only 5 variables available within 24h (vs Ranson's 48h assessment), with comparable AUC of 0.82 for mortality prediction.
Section 2
Formula & Logic
Scoring Variables (1 point each)
BUN > 25 mg/dL (> 8.9 mmol/L)
Impaired mental status (GCS < 15, disorientation, lethargy, or stupor)
SIRS — ≥ 2 of: temp < 36°C or > 38°C, pulse > 90 bpm, RR > 20 or PaCO₂ < 32 mmHg, WBC < 4k or > 12k or > 10% bands
Age > 60 years
Pleural effusion on imaging
Mortality by Score
BISAP Score
In-Hospital Mortality
0
< 1%
1
1.9%
2
3.6%
3
7.4%
4
12.7%
5
22.5%
Section 3
Pearls/Pitfalls
Clinical Pearls
Score ≥ 3: High risk for severe AP — arrange ICU, specialist GI/HPB review, early imaging (CT at 48–72h).
BUN > 25 at 24h is the single strongest individual predictor of mortality in BISAP.
Pleural effusion on CXR or CT confers significantly worse prognosis — actively look for it.
BISAP can be applied when Ranson criteria cannot be completed (e.g., 48h labs unavailable).
Section 4
Next Steps
Clinical Actions
01
BISAP 0–2: Moderate severity → IV fluids (Lactated Ringer's preferred), analgesia, NBM initially, monitor response at 12–24h.
02
BISAP ≥ 3: Severe AP → ICU admission, aggressive fluid resuscitation, early surgical/HPB consultation, ERCP if gallstone aetiology and cholangitis.
03
All: Identify aetiology (gallstones, alcohol, hypertriglyceridaemia, drugs); arrange CT at 72h if no clinical improvement.
04
Nutrition: Enteral nutrition via NG/NJ tube preferred over parenteral if tolerated; dietitian input.
Section 5
Evidence Appraisal
Validation Metrics
Metric
Value
AUC (in-hospital mortality)
0.82
BISAP vs Ranson AUC
Comparable
Time to assessment
24 hours from admission
Primary Reference
The early prediction of mortality in acute pancreatitis: a large population-based study
Wu BU et al. • Gut. 2008;57(12): 1698–1703
Section 6
Literature
Development
Developed by Bechien Wu and colleagues at Massachusetts General Hospital, Boston, published in Gut in 2008. The score was derived from a population-based retrospective analysis of 17,992 episodes of acute pancreatitis from a US claims database. The goal was to create a simple, single time-point (24-hour) alternative to Ranson Criteria that did not require a 48-hour assessment window.
Comparative Performance
Multiple validation studies have confirmed BISAP's AUC of approximately 0.82 for mortality, comparable to Ranson Criteria and APACHE II but with the practical advantage of single-time-point assessment requiring only routine clinical and laboratory data. The BUN component has been independently validated as the single strongest early predictor of pancreatitis mortality. BISAP is now included in ACG, AGA, and ESGE pancreatitis guidelines.
