CT characteristics of recurrent acute pancreatitis and acute pancreatitis in different stages-a retrospective cross-sectional study

Background: Acute pancreatitis (AP), recurrent acute pancreatitis (RAP), and chronic pancreatitis (CP) are a continuum of the same disease. The course of RAP and AP is a dynamic process. Previous studies are contradictory regarding the severity of RAP and AP. We conducted this study to investigate the computed tomography (CT) characteristics of RAP and AP in the early and late stages; respectively. Methods: Patients who underwent contrast-enhanced computed tomography for symptoms during RAP or AP episodes were retrospectively collected from three tertiary hospitals in Sichuan Province, China from January 2015 to December 2019. The patients were categorized into RAP and AP groups based on recurrence and initial events. Both the RAP and AP groups were divided into early (first week) and late stages (after the first week) based on the 2012 revised Atlanta classification (RAC). Patient demographic data, RAC, CT findings, CT severity index (CTSI) scores, and extrapancreatic inflammation on CT scores in the early and late phases were analyzed between the two groups. The Wilcoxon signed-rank test, chi(2) test, and Fisher's exact test were used to compare continuous and categorical variables between the two groups respectively. Results: In 683 RAP and 1,829 AP patients, the most common etiologies were hypertriglyceridemia and cholelithiasis, respectively. The RAP group had lower extrapancreatic inflammation on CT scores and Acute Physiology and Chronic Health Evaluation. scores than the AP group in the early stage (both P<0.001). The RAP group had higher CTSI scores than the AP group in the late stage (P=0.022). Conclusions: Compared with AP patients, the most common cause of RAP patients was hypertriglyceridemia in China, and the severity of RAP was lower than that of initial AP in the early stage and higher than that of initial AP in the late stage.