The CT severity index for acute pancreatitis is a tool used to assess the condition's severity by examining two key inputs: the findings on a CT scan and the extent of pancreatic necrosis. These factors are each assigned specific scores that contribute to an overall severity score.

For the CT findings, evaluations are categorized and scored as follows:
- Normal pancreas: 0 points
- Focal or diffuse pancreatic enlargement: 1 point
- Pancreatic inflammation and/or peripancreatic fat: 2 points
- Single peripancreatic fluid collection: 3 points
- Two or more fluid collections and/or presence of retroperitoneal air: 4 points

The extent of necrosis is assessed similarly:
- No necrosis: 0 points
- Necrosis of one-third of the pancreas: 2 points
- Necrosis of half of the pancreas: 4 points
- Necrosis of 50% or more of the pancreas: 6 points

Each selected input reflects specific clinical observations and is converted into a corresponding numerical score. These scores are then summed to determine an overall score, which can range from 0 to 10.

The interpretation of the total score provides crucial insights into the patient's prognosis:
- Scores between 0 and 3 suggest a low risk, with associated morbidity at 8% and mortality at 3%.
- Scores from 4 to 6 indicate a moderate risk, where morbidity increases to 35% and mortality to 6%.
- Scores of 7 or above signify a high risk, with substantial morbidity at 92% and mortality at 17%.

This scoring system offers a quantitative method to infer the severity of acute pancreatitis, guiding clinicians in their decision-making process for patient management.

The CT Severity Index (CTSI) for Acute Pancreatitis is a clinical calculator used to assess the severity of acute pancreatitis in patients. It is based on computed tomography (CT) findings and is used to predict the clinical outcome of the disease. The CTSI is particularly useful in stratifying patients into different risk categories, which can guide management and treatment decisions. It takes into account factors such as the presence and extent of pancreatic inflammation, pancreatic necrosis, and extrapancreatic complications. The score ranges from 0 to 10, with higher scores indicating more severe disease. There are no specific exclusion criteria for its use, but it should be noted that the CTSI is most useful in the setting of acute pancreatitis and may not be as relevant in chronic pancreatitis or other pancreatic diseases.