Fat-modified computed tomography severity index (CTSI) is a better predictor of severity and outcome in patients with acute pancreatitis compared with modified CTSI

The amount of intra-abdominal fat on CT correlates positively with the severity of acute pancreatitis (AP). The objective of the study was to evaluate a fat-modified CT severity index (FMCTSI) and compare its performance with MCTSI. For this retrospective study, 99 patients with AP who underwent contrast-enhanced CT between 3 and 7 days after pain onset were divided into a training cohort (n = 75) and a validation cohort (n = 24). MCTSI was calculated. The total adipose tissue (TAT), visceral adipose tissue (VAT), and total to visceral fat ratio (TVFR) were computed using semi-automatic software. These parameters were given a score of 1–3. FMCTSI was calculated by adding the fat score to MCTSI. Concordance for diagnosing the severity of AP was assessed. Areas under receiver operating characteristic curves (AUC) for predicting clinical outcomes were compared between FMCTSI and MCTSI. The diagnostic performance of the FMCTSI in the validation cohort was also evaluated. In the training cohort, our proposed FMCTSI performed better than MCTSI for all the outcome parameters. The highest concordance for the severity of AP was achieved for VAT-MCTSI. For all outcome parameters, the highest AUC was seen for TVFR-MCTSI. In the validation cohort, the FMCTSI achieved diagnostic performance similar to the training cohort with the highest AUC for TVFR-MCTSI. FMCTSI is a better CT index than MCTSI for predicting the severity and clinical outcomes of AP. Among the various FMCTSI parameters, TVFR-MCTSI is the best performer.