Localized ductal dilatation in both breasts refers to the manifestation of dilatation of breast ducts in both breasts, which can be divided into physiologic and pathologic, as follows. 1. Physiological: Considering the thickening and expansion of breast ducts during breastfeeding, the milk secreted by the breast can be smoothly discharged out of the body through the breast ducts, and localized ductal dilatation of both breasts may appear in ultrasonography at this time. 2. Pathological: commonly seen in ductal dilatation, which is a kind of breast disease with a long course and easy to be repeated, and may be related to obstruction of milk ducts, bacterial infection, abnormal blood hormone level and other factors; mainly manifested as localized lumps in the breast, breast pain, nipple inversion and nipple overflow. There are many reasons for localized ductal dilatation in both breasts, so patients are advised to further clarify the reasons and follow the doctor’s instructions to standardize the treatment if necessary.