Abstract： Objective:To evaluate the MRI characteristics of breast edema in idiopathic granulomatous mastitis and the associated clinical and radiological factors.Materials and Methods:This retrospective study included 129 patients with idiopathic granulomatous mastitis(IGM)from January 2021 to December 2022 in our hospital.All patients were proved by biopsy or surgical pathology and underwent breast MRI before biopsy.The course of disease,serum prolactin(PRL)and vascular endothelial growth factor(VEGF)were collected.The presence or absence of retroareola involvement,the depth of breast involvement,the number of quadrants and the extent of involvement were analyzed from breast magnetic resonance images.Then the appearance of breast edema on T2WI images and breast edema score(BES)were evaluated.The differences in these clinical and radiological characteristics between with and without breast edema groups,and between no or slight breast edema and moderate to severe edema groups were compared with χ2 test and t test.The logistic regression was used for multivariable analysis of significant variables.Results:Among the 129 patients with IGM,124 cases involved unilateral breast and 5 cases involved bilateral breasts.And totally 139 breasts were analyzed.There were 127 breasts with breast edema(91.4%)and 12 breasts with no breast edema(8.6%).For BES estimation,there were 12 breasts with BES 1(8.6%),15 breasts with BES 2(10.8%),68 breasts with BES 3(48.9%)and 44 breasts with BES 4(31.7%).On multivariate analysis,the significant independent predictors for MRI breast edema features was extension of the lesion[P=0.003,odds ratio(OR)=1.091,95%confidence interval(CI):1.035-1.150],the significant independent predictors for the moderate to severe breast edema features were serum PRL,VEGF and extension of the lesion(P＜0.05),OR=22.807(95%CI:2.281-228.008),24.140(95%CI:2.937-198.409),1.102(95%CI:1.035-1.174),respectively.Conclusions:The incidence of breast edema on MRI is high in IGM,and the degree of breast edema is related to the levels of serum PRL and VEGF and the extent of the lesion.