Superior penile girth retention with stromal vascular fraction-enriched autologous fat grafting: a retrospective 1-year comparative study

Introduction

Background

Penile size and morphology play a central role in male body image, sexual confidence, and psychological well-being (1). Historically, enlargement techniques have ranged from external devices (traction, vacuum pumps, and others) to surgical interventions such as suspensory ligament release, dermal grafts, injectable fillers, or autologous fat transfer (2-4).

Compared to other approaches, autologous fat grafting has numerous advantages, such as abundance of adipose tissue and absence of complications associated with synthetic fillers. Nevertheless, clinical outcomes are not always predictable and stable, with reported resorption rates ranging from 10% to 90% (5), often leading to asymmetry, nodularity, or substantial volume loss (6). These unfavourable effects are mainly attributed to ischemia, insufficient revascularization, and cell death of transplanted adipocytes (7).

Recent developments in regenerative medicine have prompted growing interest in stromal vascular fraction (SVF), a heterogeneous cell population found in adipose tissue. SVF includes adipose-derived stem cells (ADSCs), endothelial progenitors, fibroblasts, and other cells involved in regenerative processes (8,9). Notably, SVF enhances graft survival by promoting angiogenesis, modulating inflammatory responses, and supporting extracellular matrix remodeling (10,11). Several studies in breast reconstruction, facial aesthetic procedures, and related fields (12-14) have reported improved volume retention compared with conventional fat grafting techniques.

Rationale and knowledge gap

At the same time, experience with SVF-enriched grafting for aesthetic penile enlargement remains limited. To the best of our knowledge, no previous studies have specifically investigated the use of SVF for aesthetic penile girth enhancement. Other penis-related SVF/ADSC studies were focused mainly on Peyronie’s disease (15) or erectile dysfunction treatment via intracavernous injections (16). Given the unique anatomical features, vascular organization, and functional demands of penile tissue, there is an unmet clinical need for the assessment of the safety and efficacy of SVF-based approaches in penile augmentation.

Objective

In this retrospective comparative study, we aimed to assess the safety and clinical outcomes of SVF-enriched autologous fat grafting for penile girth enlargement versus the conventional Coleman fat technique (17). Exploratory outcomes included penile length, erectile function, and patient-reported satisfaction with the procedure. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0415/rc).

Methods

Patients

The study protocol is summarized in Figure 1. A retrospective single-centre longitudinal study was conducted between January 2021 and June 2024 at the UK private clinic 51 Harley Street Limited (London). The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The clinic (51 Harley Street Limited, London, UK) waived ethical approval, as this retrospective study utilized an anonymized internal database of the private clinic’s commercially available treatment. All patients provided written informed consent. Two patient cohorts were involved: 50 patients who chose to undergo penile girth enlargement by a novel SVF-based approach and 38 patients who were treated at the clinic during the study period but preferred a previously established Coleman fat method. All patients were potentially eligible for either of the two approaches and were asked to choose their preferred treatment. Treatment allocation was based solely on patient preference; there were no doctor-imposed restrictions, cost differences, or other external factors that could have influenced the choice. No randomization was conducted. Inclusion criteria for both groups were as follows: adult biological males aged ≥18 years seeking penile girth enhancement, with normal erectile function or mild erectile dysfunction, defined as an International Index of Erectile Function-5 (IIEF-5) score of ≥22 or 17–21, respectively (18). Exclusion criteria comprised any penile pathology, including Peyronie’s disease; any prior penile surgery or penile augmentation procedure, including implants or fillers; coagulopathy or anticoagulant therapy; active local or systemic infection; and scores 16 or less on IIEF-5. Due to the retrospective study design, no a priori power analysis was performed; sample size was determined by the number of potentially qualifying cases during the study period.

Figure 1 Overview of study design. Full IIEF, International Index of Erectile Function—full version; IIEF-5, International Index of Erectile Function—the 5-item version; n, number; SVF, stromal vascular fraction.

Before the surgery

At the initial appointment, a doctor measured patients’ penile circumference (at mid-shaft) and length (from pubic bone to tip of the glans) in flaccid and erect states. Patients were in the standing position with the penis held parallel to the floor (19). Erection was achieved by self-stimulation in the private environment (20); patients with mild erectile dysfunction were instructed to take their usual medication, if applicable. All the measurements were taken at room temperature (+20–22 °C) by the same doctor. Then patients were asked to complete the IIEF-5 questionnaire (18). Patients with mild erectile dysfunction (n=10 and n=17 for the Coleman fat and SVF fat groups, respectively) were additionally assessed using the full IIEF version (21) to confirm their condition.

Surgical procedures

The senior author (M.S.) conducted all surgical procedures (please see Figure 2A,2B, and Video S1). The operation was performed under total intravenous anaesthesia. Around 80 mL of fat was harvested from the lower abdomen using low-pressure aspiration through a 2.4-mm cannula.

Figure 2 Surgical procedure. (A) Key operative steps. (B) Preoperative and immediate postoperative appearance. These images are published with the patient’s consent. SVF, stromal vascular fraction.

For the SVF fat group, a mechanical SVF extraction approach was applied based on the previously described protocol (22). Briefly, harvested lipoaspirate was decanted (gravity decantation, 5 min), and infranatant was discarded; then, lipoaspirate was washed with sterile warm (37 °C) lactated Ringer’s solution and decanted again (1 min) followed by infranatant removal. Next, lipoaspirate was transferred to 20 mL syringes. After this, one syringe with lipoaspirate and one empty syringe were connected to the novel BMC Uniq^® SVF device (23) (please see Figure 2A and Video S1). This device is a closed system comprising an upper and lower housing, filters, and a spiral that generates a flow to support SVF isolation. The inlet and outlet ports are connected to syringes via standard Luer lock fittings (23). Around 20 manual passes are required to obtain the SVF-enriched portion. After processing in the device, the resulting suspension was centrifuged (3 min; relative centrifugal force 600 g), and the bottom pellet (that is exclusively SVF, around 0.3–0.5 mL) was mixed with the first 10 mL of fat in the first syringe to be grafted. In both groups, 40–60 mL of the prepared material was injected circumferentially along the penile shaft into the interfascial plane between dartos and Buck’s fasciae, with careful avoidance of the corpora cavernosa (Figure 2A and Video S1). To avoid potential impairment of graft vascularization, no local compression was applied after the procedure.

In the Coleman fat group, the harvested fat was processed using a Coleman technique (17), involving centrifugation (the same settings as for the SVF fat group) to remove oil and blood residues.

After the surgery

Patients attended appointments at 1, 3, 6, and 12 months after the procedure. During each of the visits, penile dimension measurements and IIEF-5 (18) scores were collected (please see the “Before the surgery” section). All the adverse events were recorded and assessed according to the Clavien-Dindo Classification (24). At the final appointment (12 months post-op), patients were asked to rate their satisfaction with the procedure on a 5-point Likert scale procedure (1—very dissatisfied, 5—very satisfied); in addition, patients who were classified as having mild erectile dysfunction at the initial visit completed the IIEF full questionnaire (21) as well.

Statistical analysis

To compare sociodemographic characteristics between groups, a two-sided Mann-Whitney test (25) and Chi-squared test (26) were employed for ordinal and categorical variables, respectively. For the penile parameters and erectile function estimates, where sample size and repeated-measures structure supported reliable longitudinal modelling, changes were analysed using linear mixed-effects models (27,28). This approach was applied to full-cohort outcomes, namely penile circumference and length in flaccid and erect states as well as IIEF-5 scores. Models included group, time, and their interaction as fixed effects, with random intercepts for each patient to account for repeated measures. The pre-treatment timepoint was used as the reference category. Models were estimated using restricted maximum likelihood, and the Wald test (29) was used to assess statistical significance. In addition to the longitudinal mixed-effects models, a two-sided Mann-Whitney test was utilized for between-group comparisons at individual time points and for change-from-baseline values. The Mann-Whitney test was also used to compare Coleman and SVF fat groups within the mild erectile dysfunction subcohort. A Bonferroni multiple comparison correction (30) was carried out where applicable. The level of statistical significance was set as P≤0.05. Python statsmodels [version 0.14.6, (27)], SciPy [version 1.15.0, (31)], and Matplotlib [version 3.11.0, (32)] packages were used for linear mixed-effects modelling, other statistical tests, and data visualizations, respectively.

Results

Patients

In total, 88 patients (Coleman fat group: n=38; SVF fat: n=50) were included in this study. Among them, 10 (Coleman fat) and 17 (SVF fat) patients were classified as having mild erectile dysfunction based on the IIEF-5 score, which was further confirmed using the full IIEF questionnaire; these patients were also analysed separately as a subcohort considering IIEF scores as an additional exploratory outcome. No patients were lost during the 12-month study period, and there were no cases of missing data.

Detailed baseline characteristics for the whole cohort and the mild erectile dysfunction subcohort are presented in Table 1 and Table S1, respectively. There were no significant differences between the Coleman fat and SVF fat groups in any case (all P values >0.05).

Adverse events

Minor wound infections (Clavien-Dindo grade II) occurred in two patients in each group during the first month post-op; all cases were resolved with oral antibiotics. There were no cases of nodules, irregularity, fibrosis, or any other adverse events. None of the patients with initially normal erection reported deterioration that would be considered erectile dysfunction according to the IIEF-5 scale, and none of the patients with mild erectile dysfunction reported further worsening of their condition (moderate or severe dysfunction).

Penile measurements

Representative images of patients from the SVF fat group are shown in Figure 3. Of note, penile length increase likely results from postural repositioning following girth augmentation rather than tissue growth; this metric was considered an exploratory outcome only. Detailed statistical outputs for each of the four penile measurements (penile circumference and length in flaccid and erect states) are shown in Tables S2-S9.

Figure 3 Representative preoperative and 12-month follow-up appearance after SVF-enriched fat grafting. These images are published with the patients’ consent. (A) Patient A, preoperative and 12-month postoperative views. (B) Patient B, preoperative and 12-month postoperative views. (C) Patient C, preoperative and 12-month postoperative views. SVF, stromal vascular fraction.

Changes in all four penile parameters are shown in Figure 4. In all cases, the following trend took place: the two groups had similar results at 1 month, but later the Coleman fat group demonstrated a faster volume loss, with a particularly notable decline at 6 months, followed by a further progressive decrease. This pattern was confirmed by the linear mixed-effects model analysis of longitudinal observations for all the penile measurements. For example, for flaccid penile circumference, the group × time interaction was significant (Wald χ²=959.291, P<0.001), indicating different longitudinal trajectories of patients from SVF fat and Coleman fat groups (please see detailed statistics in Tables S2,S4,S6,S8).

Figure 4 Longitudinal changes in penile circumference (A) and length (B) after the procedure. Changes were calculated as the difference between values at each follow-up time point and the preoperative baseline. Solid lines represent mean values, and shaded areas indicate standard deviation. SVF, stromal vascular fraction.

At 12 months, the SVF fat group showed significantly greater deltas calculated as 12-month values minus preoperative values across all metrics (P<0.001, Bonferroni-adjusted). In the Mann-Whitney test between groups, the largest effect size η²=0.728 was observed for flaccid circumference: SVF fat mean ± standard deviation (SD) 2.794±0.265 cm; Coleman fat 1.611±0.209 cm; P adjusted <0.001; results of comparisons at other time points are presented in Table S3. Please also refer to Tables S5,S7,S9 for other penile parameters.

For flaccid girth volume retention, the SVF fat group had a mean increase of 3.424 cm at 1 month and retained 81.6% of that gain at 12 months, while conventional fat grafting provided +3.192 cm at 1 month and kept 50.5% at 12 months. Other mean changes after 1 year were as follows (SVF fat versus Coleman fat): erect girth +1.9 cm versus +1.0 cm; flaccid length +1.0 cm versus +0.6 cm; erect length +0.8 cm versus +0.4 cm.

Erectile function

Erectile function was evaluated as a preliminary exploratory outcome for the whole cohort and for the mild erectile dysfunction subcohort. In the whole cohort, the group × time interaction was significant (linear mixed model analysis, Wald χ²=26.128, P<0.001), with later interaction terms favouring SVF at 6 months (β=0.819, P=0.002) and 12 months (β=1.016, P<0.001). According to the Mann-Whitney pairwise comparisons, there were significant differences for the absolute IIEF-5 values at the same time points, but those P values were non-significant after the Bonferroni adjustment (P>0.05); please refer to Tables S10,S11 for details.

Within the mild erectile dysfunction subcohort, the SVF fat group showed significantly higher scores on multiple measures in the abridged and full versions of the IIEF questionnaire (please see Tables S12,S13). For the full version, there were significant differences for domains A (erectile function) and E (overall satisfaction). For example, at 12 months, the Coleman fat group demonstrated mean ± SD 23.900±1.197 out of 30 points for domain A, while the SVF fat group reported 26.176±1.237 points; effect size η²=0.432; P adjusted=0.002. Moreover, at 1 year after the procedure, 15 of 17 patients (88.2%) who received SVF-enriched fat grafting were classified as having normal erectile function based on concordant results across both assessment scales, whereas there were no such cases in the Coleman fat group.

Patient satisfaction

At 12 months, satisfaction was significantly higher in the SVF fat group than in the Coleman fat group (mean ± SD: 4.240±0.822 vs. 3.737±1.005; η² =0.061; P=0.01). Specifically, in the SVF fat group, 44.0% of patients were very satisfied (5 points) and 40.0% were satisfied (4 points), while in the Coleman fat group, 18.4% and 55.3% of patients gave 5 and 4 points, respectively. Within the whole cohort, only 1 patient (Coleman fat) was very dissatisfied. None of the patients reported discomfort in the penis.

Discussion

Key findings

To our knowledge, no prior studies investigated the effects of SVF-enriched fat grafting exactly in the context of aesthetic penile surgery. Compared to Coleman fat, the SVF fat group demonstrated both greater and more stable circumference gain (primary outcome), indicating an advantage of utilizing regenerative cells. As an explorative outcome, we also observed an increase in penile length that likely reflects positional effects due to enlarged shaft circumference. Almost all the significant P values (P<0.05) remain significant after the Bonferroni adjustment. Of note, assessment of penile girth and length in both flaccid and erect states at four postoperative time points likely provided a more comprehensive characterization of results.

As an additional preliminary explorative outcome, we observed a statistically significant improvement of erectile function in patients with mild erectile dysfunction from the SVF fat group (Tables S12,S13). In the whole cohort, IIEF-5 changes were relatively small in absolute magnitude, and the corresponding P values did not remain significant after adjustment for multiple comparisons (Tables S10,S11). These results are therefore interpreted mainly as driven by improvement in the mild-dysfunction patients, as supported by the dedicated subcohort analysis. Previous preclinical (33,34) and clinical (16) papers demonstrated that SVF/ADSC has potential benefits in erectile dysfunction treatment, but those studies most commonly employed intracavernosal injections (16,33,35), which may be more traumatic. In contrast, the present study involved subcutaneous injections, suggesting that clinically meaningful effects for mild cases may be achieved without intracavernosal administration.

Regarding the SVF isolation workflow, the implemented approach (22) has important practical advantages for the penile girth augmentation procedures. Specifically, the protocol is fully mechanical, thereby avoiding additional regulatory, logistical, and financial constraints associated with enzyme-based methods. All protocol steps, including centrifugation, could be completed in approximately 10–15 min, allowing SVF preparation to be seamlessly integrated into standard surgical workflows. The BMC Uniq^® SVF device itself is single-use, compact, and compatible with conventional syringe-based systems commonly employed in surgery. In the previous study (22), a mechanical protocol with this device demonstrated high SVF cell yields and comparable, and in some cases superior, cellular characteristics (including viability and ADSC-associated marker expression) compared with values reported for other non-enzymatic methods in the literature.

Strengths and limitations

Several limitations of the present study should be taken into consideration. Firstly, although the Coleman fat group served as a practical control, a blinded randomised design would strengthen statistical inference. Secondly, the follow-up period was limited to 12 months, which may not allow tracking the long-term stability of the achieved results and late complications. Next, erectile function assessment as a preliminary exploratory outcome was based on subjective patient reports only, so these results should be interpreted with caution. Finally, SVF-enriched fat was prepared in the operating theatre and injected immediately after processing, so cell count and other donor-related variability of SVF features were not assessed.

The generalizability and statistical power of the present findings may be limited by the single-centre design, relatively modest sample size, and the specific patient population undergoing penile girth enhancement. However, Coleman fat grafting and SVF-enriched fat grafting are widely employed in aesthetic and reconstructive practice, so similar outcomes may be expected in similar clinical settings with comparable patient selection and operative protocols.

Comparison with similar research

Importantly, other studies (1,36-38) on penile girth augmentation via autologous fat grafting used heterogeneous measurement protocols and inclusion criteria as well as, in some cases, combined fat grafting with additional procedures such as ligamentotomy (1,36,38), limiting direct comparability of reported results.

Explanations of findings

Several biological mechanisms may underlie the observed SVF-related outcomes. Stem cells secrete capillary sprouting factors (9,39); these capillaries ensure delivery of necessary molecules to the graft and thereby limit ischemia as the cause of cell death and volume loss (7). Moreover, SVF cells stimulate extracellular matrix production and remodelling (8,39), supporting a mechanically stable scaffold that also contributes to keeping the graft shape. Next, a subset of stem cells differentiates into new adipocytes (9), replacing those lost during early resorption and modulating the balance between degradation and regeneration. Besides, SVF attenuates pro-inflammatory signalling (8,9), protecting the graft. The aforementioned local effects also could potentially spread beyond the injection sites via paracrine mechanisms and impact endothelium (39,40), contributing to the observed improvement of erectile function in mild cases. Collectively, these processes support integration of SVF-enriched fat grafts into the local penile tissue microenvironment.

Implications and actions needed

Further improvements in penile girth enlargement approaches may involve prospective randomised studies with larger cohorts and longer follow-up, deeper characterisation of SVF-related effects, and the evaluation of additional procedures aimed to enhance graft retention. Based on our preliminary findings, beyond aesthetic outcomes, SVF-enriched fat may also hold therapeutic potential for patients with mild erectile dysfunction, and this area could be explored in future dedicated clinical studies.

Conclusions

In this comparative study, SVF-enriched fat grafting was associated with greater volume retention and higher patient satisfaction versus the Coleman technique. A favourable safety profile was observed, with only minor wound infections. Furthermore, patients with mild erectile dysfunction from the SVF fat group also had a significant improvement in erectile function, suggesting a potential additional therapeutic benefit. In line with the expanding use of SVF in aesthetic and regenerative medicine, the present findings also confirm the alignment of the BMC Uniq^® SVF device with point-of-care settings. Overall, our results support SVF-enriched penile fat grafting as an effective approach and provide a rationale for its future development.

Acknowledgments

The authors used Microsoft Copilot for grammar and style checking. The authors reviewed all suggestions and take full responsibility for the final version of the manuscript. Results of this research were presented at the International Society for Sexual Medicine (ISSM) World Meeting 2026 in Porto and the American Urological Association (AUA) Annual Meeting 2026 in Washington, D.C.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0415/rc

Data Sharing Statement: Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0415/dss

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0415/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0415/coif). M.S. has a consultancy agreement with the BMC Health company. He is an inventor of the device. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The clinic (51 Harley Street Limited, London, UK) waived ethical approval, as this retrospective study utilized an anonymized internal database of the private clinic’s commercially available treatment. All patients provided written informed consent.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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