diagnosis
A patient who had something injected into the face five or eight years ago usually cannot say what it was. The clinic has closed. The record was never given. The word filler was used for several different materials, and more than one of them may have gone into the same cheek on different days. This is the ordinary starting position for a removal, not an unusual one.
It changes what diagnosis means. The question is not only what is this. It is where is it, how far does it reach, what is it attached to, and what has the body built around it. Those four answers can be obtained even when the chemical identity cannot, and they are the answers an operation is actually planned from.
01When the product name is gone
Identification proceeds by narrowing rather than by naming. The first step is examination. Where the swelling or nodule is felt, whether it moves with the skin or with the tissue beneath it, whether it is tender, whether the overlying skin is thinned or discoloured, and what the face does when it moves. Palpation is not a formality. A material that slides under the fingers behaves differently in surgery from one that is fixed to the layer below it.
History narrows it further. The year of the injection matters, because the materials that were common a decade ago are not the ones common now. The number of sessions matters, because repeated injection into the same region usually means more than one material is present. The site as the patient describes it matters less than it seems: an injection described as under the eyes may have been placed in three quite different planes depending on who performed it.
Ultrasound follows. It is the first instrument in almost every case because it answers the questions that change the plan, and because it answers them in real time with the examining hand still on the face. Where the findings stay ambiguous, or where bone is involved, further tests are added in a defined order rather than all at once.
The clinic’s stated sequence is examination, then ultrasound, then a hyaluronidase response where that is indicated, then CT where bone or a wide area of distortion is in question, then biopsy where the tissue reaction itself remains unclear. Each step is added only when the step before it has left a question that would change what is done in theatre.
Not every question changes what is done. The trade name of a product injected eight years ago is interesting, and it is occasionally recoverable, but on its own it rarely alters the operation. Knowing that the material sits above the periosteum in the medial cheek and reaches to within a few millimetres of the infraorbital foramen alters everything about the operation.
Where the presentation is acute — spreading redness, heat, pain increasing over days — identification is not the first task. An active infection is diagnosed and settled first, and the question of what the material is waits until the tissue is quiet enough for the answer to be worth having.02What ultrasound can show
High-frequency ultrasound suits the face because the face is shallow. Most injected material lies within two centimetres of the skin surface, which is the range in which the resolution of a high-frequency probe is at its best. Four findings are read from it, and each of them enters the operative plan directly.
The plane
The most useful single finding is which layer the material occupies. Intradermal, subcutaneous, within or beneath the muscle, in the deep fat compartments, directly on bone. These are different operations, approached through different incisions, carrying different risks. Ultrasound shows the layer boundaries and shows the material in relation to them, which neither a photograph nor a palpating hand can do reliably.
Depth and extent
Depth is measured rather than estimated, and so is horizontal spread. A hard lump that the patient feels as one object is often only the palpable part of a sheet of material reaching well beyond it. The difference between a discrete deposit and a sheet decides whether removal is local or wide. Marking the extent on the skin under ultrasound before the operation reduces how much tissue has to be opened simply to find the edges.
Vascularity
Doppler shows blood flow, and two things are looked for. The first is the vessels running through or beside the material, which have to be respected during dissection. The second is increased flow within the lesion itself, which points to an active inflammatory process rather than a quiet deposit. A nodule with marked surrounding flow is treated differently in timing from one without, and that difference is often the reason an operation is postponed.
Echo pattern
Materials reflect sound differently. Some appear as well-defined dark pockets with little internal echo. Some appear as bright deposits with a shadow cast behind them. Some appear as a diffuse area of raised echogenicity with no clear border anywhere. The pattern is genuinely informative about how the material is likely to behave under an instrument. It is not the same thing as chemical identification, and the distinction matters more than anything else on this page.
| Finding | What it decides |
|---|---|
| Plane of the material | Which approach, and where the incision goes |
| Depth from the skin surface | Whether a cannula can reach it or an open dissection is needed |
| Horizontal extent | Whether removal is local or wide, and whether one stage is realistic |
| Vascularity on Doppler | Whether inflammation is active, and where vessels must be avoided |
| Echo pattern and border | How firmly the material is likely to be adherent to what surrounds it |
| Relation to muscle and bone | Which structures lie on the route to it |
03What ultrasound cannot show
Ultrasound does not identify chemistry. It shows how a material reflects sound, and several unrelated substances reflect sound in similar ways. A calcium-based product and a heavily calcified area of grafted fat can both produce bright echoes with shadowing behind them. A hyaluronic acid deposit and an oil cyst can both appear as a sharply bordered dark pocket. The image narrows the possibilities. It does not close them.
Time makes this harder. In the first months after an injection a material is usually discrete, with a recognisable border and a recognisable pattern. Years later the same material sits inside the fibrous tissue the body has built around it, and the fibrous tissue has an appearance of its own. What the probe records is no longer the product. It is the product and the reaction to it, mixed together and no longer separable by sound alone.
Mixtures are the common case among the people who come for this operation. Two or three materials in one region, injected years apart by different hands, produce a composite appearance that matches nothing cleanly. The honest reading there is a description of what is present in each layer, not a name.
Operator and equipment set a further limit. The same face examined by two people with different probes can produce two different accounts of extent, which is a reason to repeat the examination and to check it against what the hand feels.
The image narrows what the material could be. It does not settle what it is. The plan is built on the first of those, not the second.
04When CT is added
CT is not a better version of ultrasound. It answers different questions, and it is requested when one of those questions is genuinely on the table.
Bone
Ultrasound stops at the bone surface. It cannot see through cortex and it cannot assess what has happened underneath a long-standing implant or deposit. An implant that has rested on the frontal bone for many years can leave a depression in the outer table beneath it. That depression is invisible until the implant is out, and by then the plan should already have allowed for it. CT shows it in advance, and its depth changes what a forehead will look like after removal.
The deep midface
Material placed deep in the midface — above the periosteum in the medial cheek, in the deep pyriform space, behind the elevator muscles — sits at the edge of what ultrasound reaches comfortably, particularly where it lies under bone shadow or under a thick layer of scar. CT shows those compartments as a whole, and shows how far a deposit has tracked along them rather than only where it is thickest.
The relation to the orbit
Where an infraorbital deposit appears to extend towards or behind the orbital rim, its relation to the rim, to the orbital septum and to the orbital contents is a question CT answers well. That relation is established before an incision is chosen, not discovered during the operation.
Calcification and previous surgery
Widespread calcification and the traces of earlier facial bone surgery are both read from CT. Someone who had a reduction malarplasty or a mandibular angle procedure years ago has an altered bony surface, fixation in some cases, and scarring that follows the previous approach. Knowing that in advance changes where dissection is safe.
CT uses ionising radiation, so it is taken when a specific question requires it rather than as a routine companion to ultrasound. Where the material is confined to soft tissue and the extent is already clear, CT adds exposure without adding to the plan.| Ultrasound | CT | |
|---|---|---|
| Best at | Soft tissue layers, in real time, with the hand on the face | Bone, deep compartments, wide-area distortion |
| Plane of the material | Shown directly | Shown, with less soft tissue contrast |
| Bone erosion under an implant | Not assessable | Shown |
| Relation to the orbital rim | Limited by bone shadow | Shown |
| Blood flow | Shown on Doppler | Not shown without contrast |
| Repeatable within one visit | Yes | No |
| Radiation | None | Yes |
| Chemical identity | Not established | Not established |
05How filler, grafted fat and threads present
The three findings that come up most often look different from one another frequently enough to be worth describing, and similarly enough to be worth a warning at the end.
Hyaluronic acid filler
Recent hyaluronic acid usually appears as a well-defined pocket with little internal echo, sitting in a single plane, its border following the shape of the space it was injected into. Older deposits lose that clarity. Material that has been present for years may be surrounded by a thickened capsule, may have broken up into several smaller collections, and may sit within tissue that has changed around it.
Semi-permanent and permanent materials
Calcium-based products, collagen-stimulating products and the permanent materials that are no longer in general use tend to appear as bright echogenic material, often with shadowing behind it, and often without the clean border that recent hyaluronic acid shows. These are the materials for which imaging and clinical reasoning carry the most weight, because they do not answer to a dissolving agent and because the tissue reaction around them is usually the reason the patient came.
Grafted fat
Grafted fat that has survived looks broadly like the patient’s own fat, which is exactly why it is difficult to separate on an image. What is visible is the part that did not survive. Oil cysts appear as round, sharply bordered collections. Calcified areas appear as bright foci, and on CT may reach a density close to that of bone. A lump in a cheek treated with fat grafting years ago is usually a mixture of surviving graft, oil cyst, fibrous tissue and calcification, not a single object with a single answer.
Threads
Threads are linear, and that is the most reliable thing about them. An intact thread appears on ultrasound as a fine bright line, sometimes with its barbs visible as a repeating pattern, running through the subcutaneous plane rather than sitting as a mass. An absorbable thread that has partly degraded may no longer be visible at all, while the fibrous tract it provoked remains and is still palpable. When a patient says they can feel a thread, it is worth establishing whether what is being felt is the thread or the scar it left behind.
These patterns describe tendencies, not rules. A material may be identified confidently on one examination and remain ambiguous on the next. Where the imaging appearance and the clinical history disagree, the plan is built to accommodate both possibilities rather than committed to one of them.06Hyaluronidase as a diagnostic test
Hyaluronidase breaks down hyaluronic acid. It does not break down the collagen-based, calcium-based or synthetic polymer materials used as semi-permanent and permanent fillers. Polycaprolactone-based products such as Ellansé are among those it does not act on. That asymmetry is what makes a trial injection informative, and it is also what limits what can be concluded from it.
A clear response, where the lump softens or reduces within the expected interval, makes hyaluronic acid the likely explanation for at least that part of the deposit. It may be treatment as well as test, which is why it is often the first thing tried when the history is consistent. Where it works, an operation may not be needed at all.
No response is the weaker result, and it is the one most often over-read. An absence of response is consistent with a non-hyaluronic material. It is equally consistent with hyaluronic acid that is heavily cross-linked, or encapsulated in fibrous tissue dense enough that the enzyme does not reach it, or present in a quantity too small to account for the lump the patient is feeling. It is consistent with the lump being scar rather than product. No response narrows the possibilities without settling them.
A partial response is common, and is often the most informative of the three. A cheek that softens by half and then stops usually contains something that answered and something that did not, which is a finding about how many materials are present rather than about any one of them.
The test is also not without consequence. Hyaluronidase acts on the patient’s own hyaluronic acid as well as on the injected product, and repeated or high-dose use in a region that has already been operated on has effects of its own on the tissue. It is used because it answers a question that matters or treats a problem that exists, not to satisfy curiosity about a material causing no symptoms.
07When a biopsy is warranted
Biopsy is not a routine part of assessment. Most operations proceed on examination and imaging alone. It is considered when a question remains whose answer would change what is done, and when imaging and response testing have not produced that answer.
Three situations account for most of them. The first is a mass that does not behave like a foreign body reaction: growing steadily, fixed to deeper structures, ulcerating, or appearing in a region where nothing was ever injected. The purpose there is to exclude a different diagnosis entirely, and that purpose takes precedence over any plan for removal.
The second is a chronic inflammatory nodule that has not settled with treatment, where the distinction between a low-grade infection, including an atypical mycobacterial infection, and a sterile foreign body reaction changes the treatment completely. Culture is taken alongside histology in that situation, because the two answers are needed together and a negative result on one of them alone settles little.
The third is material removed during the operation itself. Tissue taken out is sent for examination where the appearance at surgery was unexpected, or where the nature of the reaction matters for what comes next. Multinucleated giant cells and collagen deposition around a semi-permanent filler have been identified this way, as the clinic describes it, and that finding informs whether further removal or medical treatment is likely to be needed.
What a biopsy generally does not do is name the product. Histology describes the tissue reaction, and can characterise some materials by shape and staining behaviour, but it reports what the body has done rather than what was bought. In this work that is usually the more useful answer.
08Why the plane changes the whole plan
The same material, in the same volume, injected at two different depths in the same cheek, is two different operations. That is the reason the plane is established before anything else, and the reason an ultrasound report here is written layer by layer rather than as a single conclusion.
Material in the dermis or immediately beneath it lies against the skin and against the vessels that supply it. Removal there puts the skin surface at risk: contour irregularity, thinning, discolouration, and in the worst case necrosis. The margin for error is small, and the access has to be planned so that any scar falls where a scar is acceptable.
Material in the subcutaneous fat is the most forgiving position of all. It can often be reached through a small access point, and the fat around it tolerates dissection without much consequence. This is the situation in which a cannula technique is most likely to be sufficient on its own.
Material within or beneath the muscles of facial expression is a different proposition. Through most of the face these muscles are supplied from their deep surface, which means that dissection under a muscle is dissection in the plane the motor nerve is travelling in. Material in this position is also mechanically involved in movement, which is why patients describe it as changing shape when they smile or frown.
Material resting on the periosteum is furthest from the skin and often the easiest to lift cleanly once it has been reached, because the bone gives a floor to work against. Reaching it is the problem. The route passes everything above, and in the temple, the forehead and the midface that route includes the nerves the next page is largely about.
- Intradermal and immediately subdermal
- Closest to the skin and to its blood supply. The smallest margin for error, and the plane in which an over-enthusiastic removal shows on the surface.
- Subcutaneous fat
- The most tolerant plane. Often reachable through a small access incision with a cannula or fine instruments.
- Within or beneath the mimetic muscle
- Shares a plane with the motor supply through much of the face. Dissection here is slower and deliberately more conservative.
- Deep fat compartments
- Bounded spaces that injected material tracks along. Extent is frequently greater than the palpable lump suggests.
- Supraperiosteal and subperiosteal
- Furthest from the skin and often removable cleanly once reached, but everything above it lies on the approach.
Material that has crossed planes is the harder case, and among these patients it is the more common one. Injected material does not respect the boundaries drawn in an anatomy atlas, particularly when it was placed under pressure or given over several sessions. A deposit that begins subcutaneously in the temple and tracks down beneath the muscle is described in one sentence and dealt with in two different ways within the same operation.
This is why the assessment here does not end with a yes or a no about the presence of a foreign body. It ends with a description by layer: what is in each plane, how far it reaches in each plane, and which normal structure it is sitting against. That description is what the operation is planned from, and every judgement about how much comes out is made against it.
09What the assessment is for
A diagnosis in this field is not a label. It is a map with a scale on it, and the scale is what makes the next decision possible. Someone who arrives without a product name has not lost the information that matters. What matters can still be measured, and it is measured before anything is opened.
The habit behind that is older than the practice it is now used in. Dr Kang’s published work is on breast reconstruction, buttock ptosis and nasal bone fracture rather than on the face. One of those studies measured the muscle portion and the fat portion of a reconstructed flap separately rather than as a single volume, in a series of breast reconstruction patients. It demonstrates nothing about facial surgery and is not offered as evidence for any facial operation. What it shows is a way of looking: that one mass is made of components which behave differently, and that the components are worth measuring apart.
- The order in which questions are answered
- First
- Examination and history: site, mobility, tenderness, skin condition, what changes with movement
- Then
- Ultrasound: plane, depth, extent, vascularity, echo pattern
- If hyaluronic acid is likely
- A hyaluronidase response, which may be treatment as well as test
- If bone or wide distortion is in question
- CT: erosion, deep midface, relation to the orbit, traces of previous surgery
- If the tissue reaction is still unclear
- Biopsy, with culture where infection is in the differential
- Throughout
- The finding that decides the plan is the plane, not the product name