Effect of Postoperative Metformin on Seroma Formation Following Breast Surgery: A Prospective Comparative Study
Authors: Shamsun Nahar¹*, Sk Farid Ahmed², Warda Kamal Mollik², Khadiza Ahmed 3
Institution: ¹ Department of Surgery, Ad-din Momin Medical College Hospital, Bangladesh ² Department of Breast Surgery, Japan Bangladesh Friendship Hospital, Dhaka, Bangladesh
Introduction
Postoperative seroma is one of the most frequent complications following breast and axillary surgery. Accumulation of serous fluid within the postoperative dead space may cause discomfort, delayed wound healing, repeated aspiration, prolonged drain use, infection and additional hospital or outpatient visits. Although several surgical strategies, including quilting sutures, flap fixation and appropriate drain management, have been investigated, clinically significant seroma remains common. Recent evidence supports mechanical reduction of dead space as one of the more effective preventive approaches. Metformin, an established oral antihyperglycemic drug, has also demonstrated anti-inflammatory, immunomodulatory and tissue-healing effects in experimental and translational studies. However, evidence concerning oral metformin for prevention of seroma after breast surgery remains insufficient.
Methods
This prospective comparative study was conducted from August 2025 to August 2026 among adult patients undergoing breast surgery. A total of 100 eligible patients were enrolled and allocated equally into a metformin group receiving metformin 500 mg twice daily after surgery and a control group receiving standard postoperative care without metformin. Seroma formation was assessed clinically and by ultrasonography when clinically indicated. The primary outcome was clinically significant in postoperative seroma requiring aspiration. Secondary outcomes included reduction in total seroma volume, number of aspirations, duration of drain placement, wound complications, length of hospital stay and adverse effects.
Results
Postoperative seroma requiring aspiration occurred in 8 (16.0%) patients in the metformin group compared with 17 (34.0%) patients in the control group (p=0.045). Clinically detectable seroma occurred in 12 (24.0%) patients in the metformin group and 23 (46.0%) patients in the control group (p=0.022). Mean cumulative aspirated seroma volume was significantly lower in the metformin group than in the control group (186.3±74.8 mL vs. 312.7±116.5 mL; p<0.001). Patients receiving metformin required fewer aspirations and had a shorter mean duration of drain placement. The mean number of aspirations was 1.6±0.7 in the metformin group compared with 2.4±1.0 in the control group (p<0.001), while mean drain duration was 6.2±1.7 days versus 7.5±2.1 days, respectively (p=0.001). No significant differences were observed in surgical-site infection, wound dehiscence, flap necrosis, hematoma, reoperation or readmission. Mild gastrointestinal adverse effects were more frequent among patients receiving metformin.
Conclusion
Postoperative metformin 500 mg twice daily was associated with a lower incidence of aspiration-requiring seroma, lower cumulative aspirated seroma volume, fewer aspiration procedures and shorter drain duration following breast surgery. Although these findings suggest a potential role for metformin as an adjunctive strategy for seroma prevention, larger randomized controlled trials are required to confirm its efficacy and establish its safety and clinical applicability.