How Do Fat-Dissolving Injections and CoolSculpting Differ? (Device-Based Body Contouring I)

The full text of my column in the September 2026 issue of D&PS.

Which Complications Matter in Injection Lipolysis and Liposuction?

More than 20 years ago, I performed a substantial number of liposuction and injection-lipolysis treatments for localized fat. The injection approach was then known as HPL. Variations are still offered by clinics under different proprietary names.

The historical formulation discussed here used a base of 400 mL saline and 600 mL sterile water, with 0.25 mL of 1:1000 epinephrine, 1 mL dehydrated alcohol, 2 mL potassium chloride, 0.5 mL verapamil and 2 mL triamcinolone at 10 mg/mL.

Epinephrine is a catecholamine that activates β-adrenergic receptors, adenylate cyclase and cyclic AMP signaling to stimulate lipolysis. The formulation’s proposed rationale also included osmotic stress and adipocyte swelling. Alcohol was intended to disrupt lipid interfaces and reduce lipid clumping, while potassium chloride was included to alter the ionic and osmotic environment.

Verapamil is a calcium-channel blocker. In the proposed formulation, interference with calcium-dependent cellular homeostasis was intended to increase swelling and membrane disruption. More recent experimental work has also examined whether lowering elevated cytosolic calcium in obesity can influence autophagy and lipid metabolism.

Triamcinolone is a glucocorticoid. It suppresses phospholipase A2 and NF-κB signaling and reduces expression of COX-2, IL-6 and IL-8, as well as vascular permeability. Its intended role was to limit the secondary edema and inflammatory response after tissue injury.

The ingredients were combined with the aim of coordinating adipocyte disruption, lipid breakdown and inflammation control. Their risks require close attention: local vasoconstriction and systemic catecholamine effects, including hypertension and tachycardia; steroid-related skin atrophy and pigment changes; and hypotension associated with calcium-channel blockade.

Why Can Skin Necrosis Occur After Fat-Dissolving Injections?

Tissue injury after injection lipolysis is multifactorial. Poorly soluble steroids such as triamcinolone acetonide can persist as microcrystals in subcutaneous tissue. Effects on fibroblasts, collagen turnover and lymphatic pathways may cause fat atrophy and hypopigmentation. These changes often improve over several months to a year and should be distinguished from true necrosis.

One major mechanism of necrosis is ischemia from excessive epinephrine-induced vasoconstriction. Repeated injection into the same area, exposure to concentrated 1:1000 solution or intravascular placement raises the risk. Underlying vascular disease, including diabetic angiopathy, atherosclerosis or Buerger’s disease, can further increase tissue vulnerability.

Inadvertent intradermal or intravascular placement of alcohol-containing or concentrated formulations can cause vascular occlusion, microthrombi and chemical tissue injury. Excess cytotoxicity, adipocyte necrosis and secondary inflammation may extend into surrounding normal tissue, potentially causing irreversible skin or fascial damage.

Figure 1. Proposed complementary actions of an injection-lipolysis mixture on adipocyte disruption, lipid release, inflammation and tissue remodeling.

Liposuction Indications and Skin Elasticity

Liposuction is a common aesthetic operation with generally high patient satisfaction, but suitability and outcomes depend strongly on the region’s anatomy and skin quality.

When skin recoil is good, areas such as the flanks or love handles, outer-thigh saddlebags and inner knees can respond well. The lower abdomen can also show a balanced result in younger patients with adequate elasticity. Poor recoil, however, increases the risk of surface irregularity and sagging.

Post-liposuction waviness is sometimes described as a corrugated or undulating sheet-metal appearance. It commonly reflects excessive removal, uneven residual fat thickness or an irregular interface beneath the skin. Disruption of fibrous septa and inconsistent suction depth can also contribute.

The risk is greater in older patients and in those with poorly elastic skin or thin fat layers, particularly after aggressive superficial removal. Inner thighs and inner arms require careful selection because the skin is thin and prone to laxity. In some patients, the inner thigh may be unsuitable for suction alone. Outcomes in the upper abdomen, anterior axillary folds, back rolls and neck also depend on fat distribution and individual anatomy. Thorough assessment is essential.

Figure 2. Normal tissue versus post-liposuction rippling: skin, subcutaneous fat and fibrous septa, with contributing mechanisms.

Post-Liposuction Rippling

The so-called sheet-metal effect is a form of surface irregularity, rippling or waviness. It develops when fat removal is uneven or the skin cannot retract smoothly over its new contour. Limited elasticity and reduced tissue recovery capacity increase susceptibility.

Over-removal or excessively superficial suction can leave the skin unable to adapt to the reduced volume. Tissue friction and healing may then produce fibrosis and adhesions, creating firm irregular areas. Inadequate postoperative compression can allow fluid to accumulate and interfere with tissue settling.

Careful planning, consistent technique and preservation of an even residual layer can reduce irregularity, asymmetry, adhesions and depressions. Selection is especially important for less elastic regions such as the inner thighs and arms.

Mild waviness may improve as healing progresses. More pronounced or persistent changes may require additional treatment, such as appropriate massage, RF, microfat grafting, limited revision liposuction or selected ultrasound tightening. Severe cases may need skin excision and tissue rearrangement.

Reducing complications requires attention throughout the process: anatomical assessment, precise surgery, compression and follow-up. Experience, realistic consultation and appropriate patient selection all influence the result.

Liposuction’s effect depends on skin recoil and the amount and distribution of fat. Well-selected areas can show substantial improvement, while regions at greater risk of laxity or irregularity require a more limited, cautious approach.

How Do Devices Such as CoolSculpting Reduce Fat?

Energy-based devices use different physical mechanisms to address body contours. Depending on the system, they may target fat alone or combine fat reduction with skin tightening or muscle stimulation.

CoolSculpting

CoolSculpting is a noninvasive contouring system based on cryolipolysis. It uses the relative sensitivity of adipocytes to cold to induce apoptosis within a selected subcutaneous fat layer.

An applicator holds the tissue to be treated, often with vacuum assistance, and exposes it to precisely controlled cooling, with settings around −10°C in the protocols discussed here. Lipid crystallization and cellular injury initiate the subsequent adipocyte-clearance process.

The treatment is designed to preferentially affect fat while limiting injury to adjacent skin, nerves and muscle. Over the following weeks, macrophages and normal clearance pathways remove damaged cells and the fat layer gradually becomes thinner. Clinical studies support this mechanism and its use for localized fat reduction.

Applicators vary in shape and size to accommodate different regions. Vacuum cup designs fit projecting deposits such as the abdomen and flanks; flatter designs address broader surfaces such as the outer thighs. Smaller applicators, including CoolMini, have been used for defined areas such as submental fat.

Cooling cycles commonly last 35–60 minutes, depending on the applicator and area. Several cycles may be planned according to the deposit’s thickness and extent. Studies often report approximately 20% local fat-layer reduction after one treatment, with reassessment and possible repeat treatment at two- to three-month intervals.

A prescribed post-treatment massage is commonly performed after cooling. Reports suggest it may improve the fat-reduction response and support local circulation. Larger areas may be treated with multiple applicators, with the combination selected according to contour and tissue thickness.

When skin elasticity is poor, cryolipolysis alone may not provide the desired contour, and a tightening adjunct such as RF may be considered. Studies of a single abdominal or flank treatment reported ultrasound-measured reductions of 2.0–5.1 mm (20–32%) and caliper reductions of 2.3–7 mm (15–22%). Mean waist reductions of 2–5 cm and visible improvement in most participants have also been reported.

The main advantages are noninvasive treatment, no surgical incision or anesthesia, and a generally prompt return to everyday activities. The reduction in treated fat cells can be long-lasting, although weight change can still alter the contour. A range of applicators allows treatment of different areas and, with suitable equipment, more than one area at a time.

The amount of fat removed in one session is limited, and major weight loss should not be expected. Results develop over weeks rather than immediately. Paradoxical adipose hyperplasia (PAH), in which the treated fat enlarges instead of shrinking, can occur and may require surgical correction. Temporary bruising, tenderness and reduced sensation are also possible after suction and cooling.

(To be continued in the next issue)

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