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Autologous Fat Injection — Historical Bulking Agent

Periurethral injection of unprocessed or minimally processed autologous fat should not be used as routine treatment for stress urinary incontinence (SUI). The placebo-controlled trial found no demonstrated benefit over saline and included a fatal pulmonary fat embolism. Its relevance today is understanding prior treatments and distinguishing them from investigational cell-based therapies.[1][2]

Why the Approach Was Studied​

Fat could be harvested from the patient's own subcutaneous tissue and used to increase periurethral bulk. Autologous origin reduces concern about an immune response to foreign donor tissue, but it does not eliminate infection, necrosis, inflammation, embolism or harvest-site harm. The procedure also has costs even when no commercial implant is purchased.

Early uncontrolled series appeared encouraging. In one study, seven of nine women who continued repeated treatment reported lasting improvement; the initial cohort contained 15 women and six men. A selected responder denominator is not evidence of efficacy in all treated patients, and such reports cannot outweigh the subsequent randomized safety finding.[3]

The Placebo-Controlled Trial​

Lee and colleagues randomized 68 women, 35 to fat and 33 to saline. Complete three-month results were available for 27 and 29, respectively. The study stopped early after a treatment-related death.[1][2]

OutcomeFatSalineInterpretation
Patient-reported cure or improvement at three months6/27 (22.2%)6/29 (20.7%)No demonstrated benefit; not a 12-month cure rate.
Recorded complications per injection29/91 (32%)11/98 (11%)Injection-level events across repeated treatments, not unique-patient risk or a patient-level number needed to harm.
Urinary retentionSix patientsNoneClinically important harm in a small trial.
Fatal pulmonary fat embolismOne patient, three days after her second injectionNone reportedA treatment-related death prompted termination.

The Cochrane review's RR 0.98 referred to failure to improve, not the proportion cured. The trial's small size and early termination limit precision, but absence of demonstrated benefit together with a fatal complication supports abandoning this technique for routine urethral bulking.[2]

The review recorded misplacement during 17/91 fat injections versus 6/98 saline injections, including intraurethral, intravaginal or intravesical placement. These are procedure counts. The review assigned two liposuction-site infections to patients in the saline group.[2]

The 2017 Cochrane article incorporated a trial search ending in November 2010. It remains relevant to this historical technique, but its publication year should not be mistaken for contemporary surveillance of every bulking product.[2]

Embolism and Local Tissue Response​

A separate case report described pulmonary embolism after periurethral fat injection requiring temporary ventilatory support; that patient survived. The reports establish a serious hazard, not a precise embolism incidence for all fat-grafting procedures.[4]

Fat entering the circulation can embolize. Avoid a simplistic promise that autologous tissue cannot migrate or cause inflammatory injury. Mouse and rabbit graft experiments demonstrate site-dependent adipocyte death, regeneration, fibrosis and resorption, but they do not establish a universal 17–49% human periurethral resorption rate or prove that the urethra is uniformly avascular.[5][6][7]

Historical studies of ordinary fat injection for male incontinence or VUR were small and unfavorable. In the VUR series of 12 transplant candidates with 17 ureters, only one ureter stopped refluxing. These observations do not support another current urologic indication.[3][8]

Cell-Based Research Is a Different Intervention​

Processed adipose-derived regenerative cells, stromal vascular fraction and cultured muscle-derived cells are heterogeneous investigational products. Some protocols combine cells with adipose tissue or a scaffold. They cannot be grouped together as either the old fat-bulking technique or proven functional sphincter regeneration.

  • ADRESU: a multicenter single-arm study enrolled 45 men with persistent mild-to-moderate post-prostatectomy SUI. The reported proportion with more than 50% reduction in pad-test leakage at 52 weeks or last assessment within that period was 37.2%. No serious events were attributed to the regenerative cells. Without a control group, this does not establish comparative efficacy or exclude rare harm.[9]
  • Longer adipose-cell follow-up: a 13-man series reported mean leakage changing from 260.7 to 152.7 g/day overall. The larger quoted reduction, 281.5 to 119.0 g/day, applied only to the ten responders. Do not present the responder-only reduction as the result for all 13 men.[10]
  • Larger muscle-cell trial: iltamiocel is not a fat product. A 2024 placebo-controlled study randomized 297 women and did not meet its primary endpoint: at least 50% reduction in stress-leak episodes occurred in 52% versus 53.6% at 12 months. A favorable prior-surgery subgroup warrants further study rather than a general claim that cell therapy regenerates a functional sphincter.[11]

AUA/SUFU 2023 limits stem-cell therapy for female SUI to investigational protocols. Device clearance for a cell-processing system, autologous origin, or encouraging uncontrolled outcomes does not establish approval or efficacy of a particular SUI treatment.[12]

Evaluating a Previously Treated Patient​

Clarify the original agent and procedure: ordinary fat, a processed cellular preparation and a commercial bulking implant have different evidence and complication profiles. Reassess current incontinence type, emptying, prior operations and tissue condition. Resorption or fibrosis may contribute to recurrence, but should not be assumed to explain every new symptom.

Subsequent management follows current incontinence pathways, with treatment selected for the present findings and patient preferences. Results of fat grafting at other anatomical sites, including vocal folds or soft-tissue reconstruction, do not establish urethral efficacy or justify repeating the historical technique.

See also: Historical Bulking Agents, Bulkamid, Macroplastique.

References​

1. Lee PE, Kung RC, Drutz HP. Periurethral Autologous Fat Injection as Treatment for Female Stress Urinary Incontinence: A Randomized Double-Blind Controlled Trial. The Journal of Urology. 2001;165(1):153-158. doi:10.1097/00005392-200101000-00037

2. Kirchin V, Page T, Keegan PE, et al. Urethral Injection Therapy for Urinary Incontinence in Women. Cochrane Database of Systematic Reviews. 2017;7:CD003881. doi:10.1002/14651858.CD003881.pub4

3. Santarosa RP, Blaivas JG. Periurethral Injection of Autologous Fat for the Treatment of Sphincteric Incontinence. The Journal of Urology. 1994;151(3):607-611. doi:10.1016/s0022-5347(17)35029-2

4. Sweat SD, Lightner DJ. Complications of Sterile Abscess Formation and Pulmonary Embolism Following Periurethral Bulking Agents. The Journal of Urology. 1999;161(1):93-96. PubMed.

5. Kato H, Mineda K, Eto H, et al. Degeneration, Regeneration, and Cicatrization After Fat Grafting: Dynamic Total Tissue Remodeling During the First 3 Months. Plastic and Reconstructive Surgery. 2014;133(3):303e-313e. doi:10.1097/PRS.0000000000000066

6. Chen X, Wu Y, Liu G. Influence of Recipient Site on the Function and Survival of Fat Grafts. Annals of Plastic Surgery. 2019;82(1):110-115. doi:10.1097/SAP.0000000000001683

7. Liu B, Tan XY, Liu YP, et al. The Adjuvant Use of Stromal Vascular Fraction and Platelet-Rich Fibrin for Autologous Adipose Tissue Transplantation. Tissue Engineering Part C, Methods. 2013;19(1):1-14. doi:10.1089/ten.TEC.2012.0126

8. Palma PC, Ferreira U, Ikari O, Rodrigues Netto N. Subureteric Lipoinjection for Vesicoureteral Reflux in Renal Transplant Candidates. Urology. 1994;43(2):174-177. doi:10.1016/0090-4295(94)90039-6

9. Gotoh M, Shimizu S, Yamamoto T, et al. Regenerative Treatment for Male Stress Urinary Incontinence by Periurethral Injection of Adipose-Derived Regenerative Cells: Outcome of the ADRESU Study. International Journal of Urology. 2020;27(10):859-865. doi:10.1111/iju.14311

10. Gotoh M, Yamamoto T, Shimizu S, et al. Treatment of Male Stress Urinary Incontinence Using Autologous Adipose-Derived Regenerative Cells: Long-Term Efficacy and Safety. International Journal of Urology. 2019;26(3):400-405. doi:10.1111/iju.13886

11. Kaufman MR, Goldman HB, Chermansky CJ, et al. Iltamiocel Autologous Cell Therapy for the Treatment of Female Stress Urinary Incontinence: A Double-Blind, Randomized, Stratified, Placebo-Controlled Trial. Neurourol Urodyn. 2024;43:2290–2299. doi:10.1002/nau.25588.

12. AUA/SUFU. Surgical Treatment of Female Stress Urinary Incontinence Guideline. 2023, statement 15 and therapeutic opportunities. Guideline.