Injectable fillers are currently widely used in the clinical practice; there are many indications for injectable fillers including facial and gluteal rejuvenation, management of post-traumatic facial and pelvic disfiguring as well as management of pathological volumetric loss secondary to certain disease medications like human immune deficiency (HIV) medications .
Facial aging results from a combination of changes that involve the skin (e.g., wrinkling, dyspigmentation, and vascular changes) and underlying tissues. A progressive loss of tissue volume due to the atrophy of subcutaneous fat, as well as a reduction in structural support due to bone remodeling, contributes significantly to facial aging; the aging face becomes framed by bony contour and wrapped with thin skin resulting in deflated and fallen appearance [1, 2].
HIV-associated lipodystrophy is a syndrome that occurs in HIV-infected patients who are being treated with antiretroviral medications, although the term HIV-associated lipodystrophy refers to abnormal central fat accumulation (lipohypertrophy) and localized loss of fat tissue (lipoatrophy) [2, 3].
Fillers can be classified into short-term fillers (lasting 0–3 months), for example, collagen; medium term (lasting for 3–12 months), for example, hyaluronic acid; and long-term fillers (from 12 months to indefinitely), for example, silicone .
In the routine practice, fillers are going to be common incidental findings in the routine MRI and CT examinations done for other indications, the most important when done for metastatic work up .
Radiologists should be familiar with the specific imaging features of the injectable fillers; most of the fillers have similar imaging appearance in MRI study due to high water contents (displaying T1WI hypointense signal, T2WI hyperintense signal, lack of diffusion restriction, lack of enhancement); some fillers show filler specific imaging features: lipofilling with the specific fat signal and characteristic fat suppression on fat suppressed sequence; silicon hyperintense signal in silicon only sequence—using DIXON method—is pathognomonic for silicon filler. Calcium hydroxyapatite filler shows characteristic hyperdensity in CT studies due to presence of calcium salts [1,2,3].
Radiologists should be familiar with the characteristic anatomical locations (the common locations include nasolabial folds, superficial medial and middle cheek fat compartment, peri-oral region, glabella, and gluteal subcutaneous fat) and possible complications to avoid diagnostic pitfalls especially when incidentally discovered while imaging of other pathological process like neoplastic work up or granulomatous lesions follow-up. Radiologists should avoid false-positive diagnosis of neoplastic lesions and at the same time to avoid missing neoplastic lesions masked by the injectable fillers [4, 5].
Although considered safe by many institutions, fillers are associated with multiple potential complications, which can be classified into short-term complications and long-term complications [2, 6].
Short-term complications include allergic reaction (mostly in collagen injectables), iatrogenic infection, over injection, and maldistribution of the fillers, while long-term complications include abscess development, foreign body granulomas, migration into distant parts, and scarring with disfigurement [2, 6].
Cross-sectional imaging techniques can detect the fillers based on their imaging features and characteristic locations as well as the related complications thus guiding for safe clinical management plans .
Aim of the work
The aim of the work was to assess the role of cross-sectional imaging techniques in evaluation of the imaging features of injectable fillers and detection of their potential complications.