F2 and Cholecystitis: To achieve the prediction of severe cholecystitis, multiple clinical variables (Gallbladder wall thickness, indexes of blood routine examination, including white blood cell, alkaline phosphatase, the percentage of neutrophil, alanine transaminase, aspartate aminotransferase, fibrinogen, gamma-glutamyl transferase, prothrombin time and total bilirubin) were incorporated18.