Six studies [22, 26, 37, 46, 47, 53] reported BUN found that the activation of CB2 group could no significantly change BUN in renal dysfunction animals compared with the control group (Fig. 5A, 6 items, n = 104; SMD,− 1.09; 95% CI − 2.36 to 0.17; P = 0.09; I2 = 77%). Here, CNR2 is linked to Abnormal renal physiology.