Polyacrylamide hydrogel (PAAG) is a colorless, transparent, non-absorbable soft tissue filling material that was introduced to China in 1997 and is mainly used for rhinoplasty, breast augmentation and other surgeries. But because it can cause foreign body reaction, cysts, abscesses, skin rashes, ulcers, breasts and deformation and many other complications, it is now explicitly prohibited from clinical application. 1.Injectable breast augmentation Because injectable breast augmentation is convenient, fast, easy to operate and has small postoperative scar, it has been popular in Asia in the past few decades. PAAG contains 2.5% polyvinyl amide and 97.5% water. Water and polyvinyl amide are combined with the carboxyl end of polyvinyl amide through hydrogen bonding. From the chemical structure of PAAG, PAAG is considered to be a relatively stable, non-toxic, non-allergenic and non-absorbable substance. However, it has a high incidence of complications after injection into the human body and is difficult to extract. The occurrence of its complications is thought to be related to various factors such as the wandering nature of PAAG itself, triggering local inflammation, and the operator’s lack of knowledge about the level of injection. Although scholars at home and abroad have different views on the use of PAAG, it has not been possible to provide sufficient evidence on the safety of PAAG, and in 2006, the Chinese Drug and Food Administration issued a document banning the production and sale of PAAG and its similar products. The pathological mechanism of milk stagnation and internal fistula during breastfeeding after breast augmentation injection has not been clarified. It has been reported in the literature that in the pathological histological observation after PAAG injection augmentation, PAAG can be seen in the breast tissue, and in some cases, the destruction of breast tissue structure can be observed. During the operation of injectable augmentation mammaplasty, it is extremely important for the operator to master the level of the puncture structure, and it is especially critical to inject PAAG accurately into the posterior breast space. It is now widely believed that the obstruction of the breast ducts caused by PAAG entering the breast tissue due to misplacement of the puncture needle or damage to the breast ducts during puncture is the main cause of breast cysts. Wen-Chiung Lin et al. also suggested that the foreign body reaction to PAAG causes tissue fibrosis, which can also lead to the obstruction of breast ducts. In addition, Gavin Chun-Wui also mentioned in his article that proper breastfeeding practices are an effective measure to avoid this complication. In all cases, milk was found in the extracted purulent material and the bacterial culture was negative. In the author’s opinion, in lactating women, milk secretion is vigorous, and the obstruction of the milk ducts, the accumulation of secretions and the high pressure in the lumen trigger aseptic inflammation. If the inflammation is not controlled in time and continues to develop, the compressed milk ducts will be destroyed or dissolved, eventually leading to milk penetration from the destroyed milk duct walls into the posterior mammary space, thus forming an internal milk fistula. 3, the effect of combined drug treatment in our treatment of these three patients are in the intravenous drug anti-inflammatory based on the combined application of other drugs symptomatic treatment, which mainly include: ① magnesium sulfate, mannitol alternate external: magnesium sulfate can regulate the distribution of Ca2+ inside and outside the cell, with the role of cell protection, inhibit smooth muscle contraction, vasodilatation, etc., so as to reduce the high pressure in the mammary duct, promote blood flow, play The role of antispasmodic and pain relief, local swelling. It is salty, bitter and cold, and can be used externally to clear heat and detoxify the blood, break blood flow, disperse knots and swelling, and inhibit milk secretion; ② ethylene estradiol: ethylene estradiol can inhibit the secretion of prolactin by regulating the function of the pituitary gland, which has the effect of returning milk. The function of reducing the secretion of milk. 4. The main surgical procedures for removing hydrogel are incisional hydrogel removal and drainage, and syringe aspiration hydrogel removal. The former has the advantages of thorough cleaning of the cystic cavity and fewer operations, but there are still some shortcomings, such as the possibility of increasing the spread of pus during the cleaning of the cystic cavity, large damage to the tissue, easy infection at the incision or drainage tube after the operation, more difficult to care for, more obvious scars and slower recovery, etc.; the latter has the advantages of less trauma, faster recovery and less obvious postoperative scar, but this procedure is mostly suitable for patients in the early stage of the disease. The latter procedure has the advantages of less trauma, quicker recovery, and more obvious postoperative scarring, but this procedure is mostly suitable for patients with early stage disease, and to remove the hydrogel with high efficiency, it also depends on the accurate positioning of ultrasound and the operator’s high operational ability. 5, assessment of the disease and choice of treatment method The choice of treatment method is based on the assessment of the disease. In the early stage of the disease, local swelling, pain and other inflammatory manifestations are mild, and the fluid component of the aspiration from the punctured cyst is mainly milk. As the disease progresses, the local inflammatory manifestations gradually increase, the breast tissue is severely damaged, and the destroyed cells become necrotic and turn into pus cells, which are mixed with milk into the posterior space of the breast to form an abscess. For patients in the early stage of the disease, such as case 3, oral medication to reduce milk, magnesium sulfate and mannitol applied externally to reduce swelling and pain are more effective, and with improvement of local inflammation, hydrogel removal by syringe puncture and aspiration can be used to achieve a cure; while for patients in the late stage, incision and drainage of water and gel removal should be performed as soon as possible to thoroughly clean the abscess cavity. In the treatment of case 1, it was also found that the healing of the abscess cavity was slow after surgery, and the condition was improved quickly after switching to high-dose intramuscular injection of ethylene estradiol to enhance milk withdrawal. The main reason for this may be the persistence of the endoluminal fistula due to the severe destruction of the milk ducts and the lack of adequate milk withdrawal measures. Our treatment experience is that for patients with severe destruction of breast tissue, the treatment of milk withdrawal is particularly important, and oral treatment with ethylene estradiol and fried malt often does not achieve the desired effect, but requires high-dose intramuscular injection of ethylene estradiol with fried malt to achieve complete milk withdrawal. The prerequisite for the cure of this disease is the removal of hydrogel from the body. The combination of surgical and adjuvant treatment methods is not uniform, but should be adjusted at any time according to different situations to optimize the treatment method in order to improve the efficiency of treatment.