This chapter explores the ascending and descending migration of permanent synthetic fillers from the buttocks to the lumbosacral region and lower limbs. Magnetic resonance imaging (MRI) and ultrasound are presented as complementary tools for assessing the extent of migration, associated complications (e.g., fasciitis, fibrosis), and anatomical landmarks such as the iliotibial tract and Scarpa fascia. A novel technique, Ecomarking, is introduced as a preoperative planning tool that delineates the extent of affected tissue, aiding surgeons in designing precise and minimally invasive interventions. Doppler ultrasound is highlighted for assessing vascular compromise in migrated areas.