BISAP Score Calculator for Acute Pancreatitis

Estimate Acute Pancreatitis Severity with the BISAP Score

BISAP Score Formula

Formula

\[ \text{BISAP} = [\text{BUN} > 25\ \text{mg/dL}] + [\text{impaired mental status}] + [\text{SIRS} \ge 2] + [\text{age} > 55] + [\text{pleural effusion}] \]

Where:

\(\text{BUN}\) — blood urea nitrogen measured on admission (mg/dL); the criterion is met when BUN > 25 mg/dL
Impaired mental status — any acute alteration of consciousness (confusion, drowsiness, obtundation)
SIRS — systemic inflammatory response syndrome; at least 2 of: temperature < 36 °C or > 38 °C, heart rate > 90/min, respiratory rate > 20/min or PaCO₂ < 32 mmHg, WBC < 4 or > 12 × 10⁹/L (or > 10% bands)
Age — the criterion is met when age > 55 years
Pleural effusion — present on admission chest imaging (typically left-sided)

Each bracketed criterion counts as 1 point if met and 0 if not, so the total BISAP score ranges from 0 to 5. The score was developed by Wu et al. (2008) as a simple bedside tool to predict mortality in acute pancreatitis within the first 24 hours of admission.

BISAP Score – Calculation Example

Example: a 62-year-old patient is admitted with acute pancreatitis. BUN on admission is 32 mg/dL, the patient is alert and oriented, two SIRS criteria are present, and the chest X-ray shows no pleural effusion.

\[ \begin{aligned} \text{B} &= [32 > 25] = 1 \\ \text{I} &= [\text{alert}] = 0 \\ \text{S} &= [\text{SIRS} \ge 2] = 1 \\ \text{A} &= [62 > 55] = 1 \\ \text{P} &= [\text{no effusion}] = 0 \end{aligned} \]

\[ \text{BISAP} = 1 + 0 + 1 + 1 + 0 = 3 \text{ points} \]

Result: BISAP score = 3 points — high risk (3–5). This corresponds to a roughly 3–8% risk of in-hospital mortality in the original validation study and warrants intensive monitoring.

How to Use the BISAP Score Calculator

Enter the Blood urea nitrogen (BUN) value in mg/dL from the admission blood panel. The criterion is met only when BUN exceeds 25 mg/dL.
Select the Mental status that best describes the patient at presentation: “Alert and oriented” or “Impaired (confused, drowsy or obtunded)”.
Choose whether SIRS is present. Count the criteria listed in the field description (temperature, heart rate, respiratory rate or PaCO₂, white blood cell count); select “Present (2 or more criteria)” if at least two are met.
Enter the patient’s Age in years. The criterion is met when age is above 55.
Select whether a Pleural effusion is visible on admission chest imaging.
Read the results: the total BISAP score (0–5), the risk category, and an interpretation with a breakdown of which criteria were met.

What Is the BISAP Score?

BISAP (Blood urea nitrogen, Impaired mental status, Systemic inflammatory response syndrome, Age, Pleural effusion) is a five-point clinical scoring system used to stratify the severity of acute pancreatitis early in the hospital course. It was designed as a simpler alternative to older systems such as Ranson’s criteria and APACHE II, which require many laboratory values or repeated measurements over 48 hours. Because all five BISAP variables are available within 24 hours of admission — often immediately at the bedside — the score allows rapid triage decisions.

The score matters because acute pancreatitis has a highly variable course: most patients recover with supportive care, but a minority progress to severe disease with organ failure, pancreatic necrosis, sepsis or death. Early identification of high-risk patients allows clinicians to escalate monitoring, initiate aggressive fluid resuscitation, consider ICU admission and involve specialists sooner, which is why BISAP has been incorporated into international pancreatitis guidelines.

Interpretation is straightforward. Scores of 0–1 indicate low risk (mortality well under 1% in the original study), a score of 2 is intermediate (roughly 1–2% mortality) with risk rising per point, and scores of 3–5 mark a high-risk group, with mortality around 3–8% at a score of 3 and about 11% or higher at 4–5. Higher scores also predict increased rates of organ failure, ICU admission and pancreatic necrosis. The score should be viewed as a continuous gradient of risk rather than a single cutoff — each additional point worsens the prognosis.

Assumptions, Limitations and Practical Tips

Timing: BISAP was validated using data collected within 24 hours of admission. Applying it later, after treatment has begun, reduces its accuracy.
Units: BUN must be entered in mg/dL. If your laboratory reports urea in mmol/L or µmol/L, convert first (urea in mmol/L × 2.14 ≈ BUN in mg/dL for urea; divide µmol/L values by 2.14 to get mg/dL equivalents).
Not a diagnostic tool: BISAP estimates the probability of complications; it does not diagnose pancreatitis or its severity by itself. The diagnosis of acute pancreatitis rests on characteristic abdominal pain plus lipase/amylase elevation or imaging findings.
Etiology and comorbidities are not included: factors such as obesity, etiology (e.g. hypertriglyceridemia), renal function baseline and comorbid diseases also influence outcome and are not captured by the five criteria.
Dynamic reassessment: a persistently rising BUN over the first 48 hours despite fluids is itself an adverse prognostic sign; repeat clinical evaluation remains essential.
Clinical judgment prevails: any tool, including BISAP, should supplement — never replace — the judgment of the treating clinician.

For related bedside risk scores, see our qSOFA Score Calculator for sepsis screening, the CURB-65 Score Calculator for pneumonia severity, or the Glasgow Coma Scale Calculator if you need a structured assessment of mental status. The BISAP score is provided for informational purposes only and is not a substitute for professional medical advice.

Frequently Asked Questions

How do I calculate the BISAP score by hand?

Assign 1 point for each of five yes/no findings from the first 24 hours after admission: BUN above 25 mg/dL, any new impairment of consciousness (confusion, drowsiness, obtundation), at least 2 SIRS criteria, age over 55 years, and a pleural effusion on chest imaging. Add the points for a total between 0 and 5. No complex formula or repeated measurements are needed — every variable is binary.

What is a good or dangerous BISAP score?

0–1 is considered low risk, with in-hospital mortality well under 1% in the original study. A score of 2 is intermediate (roughly 1–2%). Scores of 3–5 are high risk: about 3–8% mortality at 3 and roughly 11% or more at 4–5, along with higher rates of organ failure and necrosis. Treat the score as a gradient — each additional point worsens the prognosis rather than crossing a single sharp cutoff.

How do I convert urea from mmol/L to the BUN mg/dL the BISAP calculator needs?

Many European and other labs report serum urea instead of BUN. Multiply urea in mmol/L by 2.14 to get the approximate BUN value in mg/dL; for values in µmol/L, divide by 2.14 (or multiply mmol/L values by 214). For example, urea of 10 mmol/L ≈ 21.4 mg/dL, which does not meet the >25 mg/dL criterion. Note that some countries use different conversion factors, so check your laboratory's reference method if the value is near the threshold.

What happens if BUN is exactly 25 mg/dL or age is exactly 55?

Both criteria use strict thresholds: the point is awarded only when BUN is greater than 25 mg/dL and age is greater than 55 years. A BUN of exactly 25 or an age of exactly 55 scores 0 for that criterion, as defined in Wu et al.'s original study and implemented in this calculator. If a value sits right at the cutoff, double-check the lab report and consider rechecking, since borderline values are also where unit-conversion errors matter most.

How does BISAP compare with Ranson's criteria and APACHE II?

BISAP was designed to be simpler and faster. Ranson's criteria require up to 11 variables collected over the first 48 hours, and APACHE II involves more than a dozen physiological measurements, so neither is practical for immediate bedside triage. BISAP uses just 5 variables available at admission, yet performs comparably in predicting mortality. Its trade-off is less granularity — it captures less detail about organ function, comorbidities and pancreatitis etiology.

Can BISAP be used in children or pregnant patients?

BISAP was developed and validated in adults with acute pancreatitis, so it should not be applied to children — the age criterion and physiological thresholds (heart rate, respiratory rate, WBC) differ in pediatric populations. Evidence in pregnancy is also limited, and elevated BUN or imaging findings may be interpreted differently. For these groups, use disease-specific pediatric obstetric assessment tools and specialist judgment rather than the BISAP score.

What are the most common mistakes when using the BISAP score?

Frequent errors include entering urea in mmol/L without converting to mg/dL, scoring SIRS as present when only one criterion is met (two are required), counting chronic confusion or dementia as impaired mental status (only acute alterations count), applying the score after 24 hours of treatment when BUN and vitals have already changed, and treating the result as a diagnosis. Always pair the score with clinical judgment and repeat assessment over the first 48 hours.

BISAP Score Calculator