Balthazar Score (CTSI) Calculator

Balthazar Score (CTSI) Calculator for Gastroenterology. Scores are grouped into mild (0 to 3), moderate (4 to 6), and severe (7 to 10). In the original 88-patient derivation, patients with a high index had roughly 92% morbidity and 17% mortality, whereas those with a low index had about 2% morbidity and no deaths. Higher scores predict longer hospital stay, greater need for percutaneous or surgical intervention, and higher rates of infection and organ failure. The score describes anatomic severity and drives surveillance intensity and readiness to escalate care; it does not by itself mandate a specific procedure, since intervention decisions hinge on infected necrosis and clinical trajectory.

How this calculator works

The CT Severity Index sums two contrast-enhanced CT findings measured at least 72 hours after symptom onset: the Balthazar grade of pancreatic and peripancreatic inflammation (grade A normal = 0, B focal/diffuse enlargement = 1, C intrinsic gland changes with peripancreatic fat stranding = 2, D single ill-defined fluid collection = 3, E two or more collections or gas = 4) plus a necrosis subscore (none = 0, up to one-third of the gland = 2, one-third to one-half = 4, over one-half = 6). The total runs 0 to 10. Necrosis is scored as the failure of the parenchyma to enhance after intravenous contrast, which is why the scan is timed after the initial 72-hour window when necrosis has declared itself.

When to use this calculator

Apply the CTSI in adults with acute pancreatitis when a contrast-enhanced CT has been obtained to grade morphologic severity and estimate the risk of local complications. It is most informative on a scan performed 72 hours or more after symptom onset, since earlier imaging underestimates necrosis. It should not be used as an admission triage tool: current guidance (revised Atlanta 2012; ACG 2013) does not recommend early CT solely for severity scoring in the first 24 hours, because clinical scores perform comparably and contrast may be withheld in dehydrated or renally impaired patients. It does not replace organ-failure assessment for defining severe disease.

Inputs used

  • CT inflammatory grade
  • Pancreatic necrosis percentage

Clinical interpretation

Scores are grouped into mild (0 to 3), moderate (4 to 6), and severe (7 to 10). In the original 88-patient derivation, patients with a high index had roughly 92% morbidity and 17% mortality, whereas those with a low index had about 2% morbidity and no deaths. Higher scores predict longer hospital stay, greater need for percutaneous or surgical intervention, and higher rates of infection and organ failure. The score describes anatomic severity and drives surveillance intensity and readiness to escalate care; it does not by itself mandate a specific procedure, since intervention decisions hinge on infected necrosis and clinical trajectory.

Worked example

A 58-year-old with gallstone pancreatitis has a day-4 contrast CT showing two separate peripancreatic fluid collections (Balthazar E = 4 points) with roughly 40% of the gland failing to enhance (necrosis one-third to one-half = 4 points). Total CTSI = 8, placing the patient in the severe band (7 to 10). This predicts a markedly elevated risk of morbidity and mortality and flags a patient who warrants close monitoring for infected necrosis and consideration of step-up intervention if clinical deterioration occurs.

Limitations and safety notes

The necrosis subscore requires intravenous contrast, so the index cannot be fully computed on unenhanced scans and is unreliable if imaging is done too early, before necrosis is radiographically evident. It weights parenchymal necrosis heavily but captures extrapancreatic complications such as vascular, gastrointestinal, or pleural involvement poorly, which is the specific gap the modified CTSI (Mortele, 10-point) was designed to close. Comparative data (Bollen 2011) show CT scoring is no more accurate than clinical scores like BISAP or APACHE-II for predicting clinically severe disease on admission, and interobserver variability in grading collections and estimating necrosis percentage is a recognized weakness.

Frequently asked questions

How is the CTSI different from the modified (Mortele) CTSI?

The original CTSI (0 to 10) combines the Balthazar grade (0 to 4) with a necrosis subscore (0, 2, 4, or 6). The modified CTSI is also 0 to 10 but simplifies inflammation to 0/2/4, compresses necrosis to 0/2/4, and adds up to 2 points for extrapancreatic complications (effusion, ascites, vascular or GI involvement). The modified version correlates more closely with hospital stay, infection, and organ failure and has lower interobserver variability.

When should the CT be done to score the CTSI accurately?

At least 72 hours after symptom onset. Necrosis is scored as non-enhancing parenchyma, and it often is not yet visible within the first day or two, so early scanning underestimates the necrosis subscore and the total index.

Does a high CTSI define severe acute pancreatitis?

No. Under the revised Atlanta classification, severity is defined clinically by persistent organ failure (over 48 hours) and local or systemic complications, not by the CT score. A high CTSI identifies extensive morphologic disease and elevated complication risk but is a complement to, not a substitute for, organ-failure assessment.

Should every patient with acute pancreatitis get a CT to calculate this score?

No. Guidelines advise against routine early CT purely for severity grading. CT is reserved for diagnostic uncertainty, failure to improve after 48 to 72 hours, or suspected complications, since clinical scores predict severity comparably and contrast carries risk in dehydrated or renally impaired patients.

References

  • Balthazar EJ, Robinson DL, Megibow AJ, Ranson JH. Acute pancreatitis: value of CT in establishing prognosis. Radiology. 1990. PMID: 2296641.
  • Mortele KJ, Wiesner W, Intriere L, et al. A modified CT severity index for evaluating acute pancreatitis: improved correlation with patient outcome. AJR Am J Roentgenol. 2004. PMID: 15505289.
  • Bollen TL, Singh VK, Maurer R, et al. A comparative evaluation of radiologic and clinical scoring systems in the early prediction of severity in acute pancreatitis. Am J Gastroenterol. 2011. PMID: 22186977.

Editorial review and citation methodology

Reviewed by the Quick Medical Calculator Editorial Team. Last reviewed: April 27, 2026. The review checks calculator inputs, intended population, interpretation, limitations, and source alignment.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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