Natural course of fat necrosis after deep inferior epigastric perforator flap-based breast reconstruction: Evaluation based on ultrasound examination

Background: Fat necrosis, often developing following deep inferior epigastric perforator (DIEP) flap-based breast reconstruction, is not a negligible complication. This study aimed to conduct a longitudinal assessment of the clinical course of fat necrosis in breast reconstruction with DIEP flap. Methods: Among patients undergoing immediate DIEP flap-based breast reconstruction between 2009 and 2017, those who developed fat necrosis on ultrasonographic examination and did not undergo surgical intervention for the lesion were reviewed. Changes in lesion size over time were assessed based on regular ultrasound examinations. Results: A total of 37 cases were analyzed, with a mean follow-up of 52.6 months (range, 19–114). Their mean age was 45.8 years, and the mean body mass index was 23.4 kg/m². Of these, 21 lesions had disappeared over time. The mean time from detection to the disappearance was 30.4 months. The remaining 16 lesions did not disappear and persisted for a median follow-up of 43.5 months. Compared with the lesions that persisted, those that disappeared were significantly smaller in initial size (p = 0.040) and had a lower inset ratio of the harvested flap (p = 0.006). The optimal cutoff value for the initial size for disappearance was ≤1.97 cm. Among the lesions >1.97 cm in size, 6 (35.3%) of 17 lesions disappeared, whereas in those ≤1.97 cm, 15 (75.0%) of 20 disappeared over time, with a significant difference (p = 0.041). Conclusion: The natural course of fat necrosis that develops following the DIEP flap may differ according to its initial size.