Objective To summarize the anatomical types of the concomitant veins of deep inferior epigastric artery and the corresponding choice of anastomosis methods, and to evaluate the indications and safety of various methods. MethodsBetween October 2015 and June 2021, 296 female patients received breast reconstruction with autologous free lower abdominal flap, including 154 cases of immediate breast reconstruction and 142 cases of delayed breast reconstruction. The average age of the patients was 36.5 years, ranged from 26 to 62 years. Unilateral free deep inferior epigastric artery perforator flap transplantation was performed in 172 cases, and unilateral free muscle-sparing rectus abdominis myocutaneous flap transplantation was performed in 124 cases. The internal thoracic vessels were selected as the recipient vessels in all cases. The length of vascular pedicle ranged from 9.5 to 13.0 cm, with an average of 11.2 cm. The concomitant veins of deep inferior epigastric artery included three anatomical types: one-branch type in 26 cases (8.8%), two-branch type in 180 cases (60.8%), and Y-shaped structure in 90 cases (30.4%). Anastomosis of inferior epigastric artery was performed with the proximal end of internal thoracic artery, while that of vein should be adjusted according to the diameter, length, wall thickness, and branches of the vein. The specific classification of venous anastomosis included: ① The sole concomitant vein of deep inferior epigastric artery was anastomosed with the internal mammary vein (26 cases); ② The two concomitant veins of deep inferior epigastric artery were anastomosed with the internal mammary vein respectively (151 cases); ③ The larger one of two concomitant veins of deep inferior epigastric artery was anastomosed with the internal mammary vein, and the other one was ligated and discarded (29 cases); ④ The two concomitant veins of deep inferior epigastric artery were Y-shaped, and the common trunk segment was directly anastomosed with the internal mammary vein (31 cases); ⑤ The smaller branch of the concomitant veins of Y-shaped structure was ligated, and the thicker branch was anastomosed with the internal mammary vein (17 cases); ⑥ The concomitant veins of Y-shaped structure were anastomosed with the internal mammary veins respectively (42 cases). Results Among the patients who underwent venous anastomosis according to scheme ④, 3 cases had venous crisis of flap after operation, of which 1 case was successfully rescued by emergency exploration; the other 2 cases had flap necrosis, of which 1 case survived after being repaired by pedicled latissimus dorsi flap, and 1 case closed the wound directly. Flaps with other venous anastomosis protocols survived completely. All 296 patients were followed up 12-70 months, with an average of 37.5 months. The reconstructed breast has good shape, good elasticity, and no skin flap contracture. The donor site of the flap only left linear scar, and the abdominal wall function was not affected. ConclusionThe method of direct anastomosis of concomitant veins of deep inferior epigastric artery with Y-shaped structure is relatively risky, and the vessels are prone to be twisted and compressed, leading to the occurrence of venous crisis. It can improve the safety of surgery if only one large vein is anastomosed or two veins are separated to anastomose respectively.