Exclusion criteria were AP in pregnancy, malignancy, traumatic AP, and acute-on-chronic pancreatitis. Three hundred and twenty-five AP patients who were referred to CT on admission at our hospital were identified by the hospital information system. Of these 325 patients, 117 were excluded for the following reasons: 99 received CT examination longer than 24 hours after AP onset or admission, 8 underwent only MRI examination and 10 had only an ultrasound examination. Consequently, 208 patients with available imaging and clinical data were included in this study (Fig. 1). Of these patients, 166 had an unenhanced CT scan and 42 had the enhanced CT scan. One hundred and twenty-one of the enrolled patients were male (58.2%), 87 were female (41.8%), and the median age was 45 years (range: 18–83 years).