Abstract: Objective To investigate the CT characteristics of acute pancreatitis (AP) in the context of preexisting fatty liver (FL) and to assess the influence of FL on AP severity and the persistence of systemic inflammatory response syndrome (SIRS).Methods Between January 2019 and March 2022, 102 patients diagnosed with AP were hospitalized and categorized into two distinct cohorts based on the presence or absence of fatty liver. Concurrently, these patients were stratified into groups experiencing either persistent SIRS or non-persistent SIRS. Comparative analyses were conducted to evaluate variations in clinical characteristics, AP severity, and the incidence of persistent SIRS between the cohorts. Employing multivariate analysis techniques, we identified salient risk factors associated with the onset persistent SIRS. Furthermore the predictive validity of fatty liver presence, APACHE II scores and MCTSI scores in forecasting persistent SIRS was rigorously examined. Results Our comparative analyses revealed significant differences in the clinical characteristics beween the fatty liver group and non-fatty liver cohorts. The fatty liver group exhibited higher incidences of alcoholism(9.4% vs. 0.04%), hyperlipidemia(39.6% vs. 18.4%), pancreatic necrosis(24.5% vs. 8.2%), and local complications(49.1% vs. 28.6%), all of which were statistically significant(P<0.05). Conversely, the incidence of idiopathic pancreatitis was considerably lower in the fatty liver group(20.8% vs. 46.9%, P<0.05). In terms of AP severity, the fatty liver group demonstrated significantly elevated rates of moderate and severe AP at 34.0% and 22.6%, respectively, compared to 26.5% and 8.2% in the non-fatty liver group(P<0.05). Similarly, the incidence of persistent SIRS was notably higher in the fatty liver group at 58.5%, as opposed to 26.5% in the non-fatty liver group(P<0.05). Additionally, mean APACHE II scores(6.26±3.84 vs. 5.0±3.0) and MCTSI scores(4.93±1.98 vs. 4.0±2.2) were significantly higher in the fatty liver cohort(P<0.05). Conversely, the proportion of mild AP cases was significantly 43.4% as opposed to 65.3% in the non-fatty liver group(P<0.05). Patients in the persistent SIRS cohort exhibited markedly elevated incidences of hyperlipidemia(42.2% vs. 15.8%), C-reactive protein level(91.2 [1.8, 357.0] mg/dL vs. 26.9 [0.2, 308.2]mg/dL), TG levels(5.2±0.8mg/dL vs. 2.2±0.7 mg/dL), pancreatic necrosis(33.3% vs. 3.5%), and local complications(64.4%, vs. 17.5%), all of which were statistically significant(P<0.05). The incidence of cholelithiasis was significantly lower in th persistent SIRS group, measured at 24.4% in contrast to 49.% in the non-persistent SIRS cohort(P<0.05). In comparing the severity of AP between the persistent SIRS group and non-persistent SIRS group, the persistent SIRS group exhibited a higher proportion of moderate(40.0% ) and severe AP(33.3%), along with elevated APACHE II scores(7.1±3.7) and MCTSI scores(5.7±1.9). These metrics were significantly higher than those in the non-persistent SIRS group, where the proportions of moderate and sever AP were 22.8% and 1.8%, and APACHE II and MCTSL scores were 4.5±2.7 and 3.5±1.8, respectively. Conversely, the proportion of mild AP cases in the persistent SIRS group was 26.7%, significantly lower than the 75.4% observed in the non-persistent SIRS group(P<0.05). Multivariate analysis identified fatty liver, an APACHE II score≥6 and an MCTSI score≥4 as independent risk factors for persistent SIRS in patients with AP. Upon evaluating the predictive value of theses factors for persistent SIRS, the flollowing results were obtained: For fatty liver, the AUC was 0.663, with a sensitivity of 0.673 and a specificity of 0.644. For an APACHE II score ≥6, the AUC was 0.701, with a sensitivity of 0.503 and a tspecificity of 0.781. For an MCTSI score ≥4,the AUC was 0.782, with a sensitivity of 0.676 and a specificity of 0.792. Conclusion Patients with preexisting FL are found to be more susceptible to developing necrosis and local complications, as evidence by CT scans. Additionally, these patients were more likely to exhibit severe AP and persistent SIRS. Importantly, preexisting FL is identified as an independent risk factor in predicting the presence of persistent SIRS in individuals with AP.

Key words: Acute pancreatitis, Fatty liver, Systemic inflammatory response syndrome