A high-degree of heterogeneity was noted in the meta-analysis of cholangitis (I2 = 80%) with a low-degree of heterogeneity noted in the choledocholithiasis (I2 = 45%) and malignancy (I2 = 30%) meta-analyses and no significant heterogeneity noted in the SOD (I2 = 0%) and acute pancreatitis (I2 = 0%) analyses. Here, SOD1 is linked to cholangitis.