Large lumps at the root of thigh after surgery may be caused by lymphadenitis, sebaceous cysts and other reasons. 1. Lymphadenitis: lymphadenitis may be caused by postoperative infection spreading to the root of the thigh, which will appear as a lump at the root of the thigh, with localized redness, swelling and pressure pain, and can be treated with medicines such as cefuroxime and ceftriaxone under the guidance of the doctor. 2. Sebaceous cysts: It may be that the secretion of sebaceous glands located in the epidermis cannot be discharged in time, and accumulate in the glands, which leads to sebaceous cysts, and there will be a large lump at the root of thighs, which can be surgically excised from the sebaceous cysts. Therefore, patients with large lumps at the root of the thigh after surgery should go to the hospital as soon as possible to clarify the cause of the disease, and carry out standardized treatment under the guidance of the doctor. Usually, you should also avoid staying up late and eat regularly.