The modified CT severity index is an extension of the original CT severity index (CTSI) which was developed by Balthazar and colleagues in 1990 for distinguishing mild, moderate and severe forms of acute pancreatitis.

The original CT severity index has been followed internationally and has been very useful. However, it has a number of limitations:

• it has been found that complications like organ failure, do not correlate well with the score given by original CTSI
• interobserver variability with original CTSI can result in different scores for the same patient
• it has been observed that patients with >30% necrosis have similar morbidity and mortality, thus including an additional 50% in the score was not practically useful

These limitations have resulted in the creation of the modified CTSI which correlates more closely with patient outcome in terms of duration of hospital stay and development of organ failure.

Modified CTSI

Scores are generated by estimating pancreatic inflammation and necrosis to give a score out of 10.

Pancreatic inflammation

• 0: normal pancreas
• 2: intrinsic pancreatic abnormalities with or without inflammatory changes in peripancreatic fat
• 4: pancreatic or peripancreatic fluid collection or peripancreatic fat necrosis

Pancreatic necrosis

• 0: none
• 2: 30% or less
• 4: more than 30%

Extrapancreatic complications

• 2: one or more of pleural effusion, ascites, vascular complications, parenchymal complications and/or gastrointestinal involvement

Total score

Total points are given out of 10 to determine the grade of pancreatitis and aid treatment:

• 0-2: mild
• 4-6: moderate
• 8-10: severe