Reverse Bilateral Anterior Scrotal Artery Flap (Gao / Qu)
The reverse bilateral anterior scrotal artery flap is a single-stage, reverse-flow axial scrotal flap that perfuses the anterior scrotal skin via retrograde flow through the anterior scrotal arteries — supplied across choke-vessel anastomoses by the posterior scrotal arterial system. The flap is distally based at the inferior / posterior scrotum, allowing it to bypass a compromised proximal pedicle at the scrotal root or penoscrotal junction. In the only published case (Gao 2019, single patient with complete post-circumcision penile skin loss), the technique produced no complications over 10-year follow-up with normal erectile function and intercourse ability.[1]
For antegrade single-stage scrotal flaps, see Fakin, Murányi, Yao butterfly, and Total Anterior Scrotal Flap (Zhao). For staged or outpatient variants, see Pribaz / McLaughlin staged and VSSF. For full framework, see Penile Reconstruction.
Rationale
Most scrotal flaps are antegrade — pedicle at the scrotal root, with blood flow from the external pudendal system distally onto the shaft. The Gao technique inverts this: the pedicle is distal / posterior, and the flap survives on retrograde flow from the perineal / posterior-scrotal system through the rich inter-territorial anastomotic network back into the anterior scrotal arteries.[1]
The principle is well established in extremity reconstruction (reverse radial forearm, reverse sural, reverse peroneal) and depends on an anastomotic substrate large enough to support reverse perfusion.[2][3] In the scrotum, the Carrera microvascular study and the Giraldo perineogenital anatomy work characterized this substrate as "widely inter-anastomosed" — denser than typical extremity choke networks.[4][6]
Vascular Anatomy Enabling Reverse Flow
Three Carrera scrotal territories[4]
| Source artery | Origin | Territory |
|---|---|---|
| Anterior scrotal arteries | Inferior external pudendal → femoral | Two lateral territories (enter at scrotal-root creases) |
| Posterior scrotal arteries | Perineal → internal pudendal | Central territory (enter posteriorly along the scrotal septum) |
Inter-territorial anastomoses
- Boundaries between the three territories carry choke anastomoses (Taylor angiosome concept)[5]
- Giraldo identified three major perineogenital anastomotic circuits — at the penile base, the scrotal septum, and the perineal fat / lateral spermatic-scrotal fascia[6]
- The "widely inter-anastomosed" description implies a higher density of true anastomoses than typical extremity choke vessels — explaining the favorable substrate for reverse flow in the scrotum
Reverse-flow mechanism
- Antegrade (normal): external pudendal → inferior external pudendal → anterior scrotal artery → scrotal skin
- Reverse (Gao): internal pudendal → perineal → posterior scrotal artery → choke anastomoses → anterior scrotal artery (retrograde) → scrotal skin
- Direct analogue of the reverse sural flap, where peroneal-artery perforator anastomoses support retrograde sural perfusion
Indications
| Indication | Notes |
|---|---|
| Complete circumferential penile skin loss | The Gao case |
| Post-circumcision skin necrosis | Most common indication described |
| Proximal scrotal root / penoscrotal junction compromised (scar, infection, prior surgery) | The defining indication — standard antegrade flaps cannot be based here |
| Posterior scrotal vasculature intact | Required substrate for reverse flow |
Contraindications
- Posterior scrotal vascular compromise — prior perineal surgery / radiation / trauma
- Scrotal skin disease — LS, lymphedema
- Prior scrotal surgery disrupting the anastomotic network
- Insufficient scrotal skin
Operative Technique
1. Debridement of the penile defect
- Excise all infected / necrotic / non-viable penile skin to Buck's fascia
- Irrigate; hemostasis
- Gao case: 20 days post-circumcision, infection + necrosis + complete skin loss; debrided before flap design[1]
2. Reverse-flow flap design
- Two bilateral scrotal flaps, one on each hemiscrotum
- Pedicle base — inferior / posterior (where the posterior scrotal arteries provide retrograde inflow through the anastomotic network)
- Free edge — superior / anterior near the penoscrotal junction
- Each flap dimensioned to half the shaft circumference × shaft length
3. Identify and divide the anterior scrotal artery proximally
- Identify the anterior scrotal artery at the scrotal root on each side
- Ligate and divide proximally — this converts the flap from antegrade to reverse flow
- Flap now depends entirely on retrograde perfusion via the posterior scrotal / anastomotic network
4. Flap elevation
- Elevate superior → inferior (proximal → distal) so the inferior / posterior pedicle remains intact
- Plane above external spermatic fascia, preserving dartos with the flap
- Tunica vaginalis kept intact
5. Flap rotation and wrapping
- Rotate the flaps superiorly from their distal pedicle onto the denuded shaft
- Right flap covers right hemi-circumference; left flap covers left hemi-circumference
6. Inset
- Sutured together along dorsal and ventral midlines of the shaft (two longitudinal suture lines)
- Distal edges to subcoronal margin / glans
- Proximal edges to penile base / pubic skin
- Interrupted absorbable suture
7. Donor closure
- Remaining posterior and inferior scrotal skin advanced and closed primarily
8. Dressing and monitoring
- Light compressive dressing; Foley catheter
- Monitor closely for venous congestion — the dominant complication mode of reverse-flow flaps[2][3]
Reverse-Flow vs Antegrade Scrotal Flaps
| Feature | Reverse (Gao) | Fakin antegrade | Yao antegrade | Murányi antegrade |
|---|---|---|---|---|
| Flow direction | Retrograde | Antegrade | Antegrade | Antegrade |
| Pedicle location | Inferior / posterior scrotum | Bilateral scrotal roots (superior) | Bilateral scrotal roots | Bilateral scrotal roots |
| Blood-supply source | Posterior scrotal → choke anastomoses → anterior scrotal (retrograde) | Anterior scrotal (antegrade) | Anterior scrotal (antegrade) | External pudendal (antegrade) |
| Bypasses compromised proximal pedicle | Yes | No | No | No |
| Venous congestion risk | Higher (inherent) | Lower | Lower | Lower |
| Evidence base | 1 case | 43 patients | 7 patients | 49 patients |
| Flap survival | 100% (n = 1) | 100% | 100% | 90% success |
Reverse-Flow Physiology
Arterial inflow
- Tanaka & Tajima: viable flap area diminishes proportionally with retrograde inflow (r = 0.885)[3]
- Adequate retrograde inflow depends on the caliber and density of inter-territorial anastomoses
- The "widely inter-anastomosed" scrotal substrate is favorable[4]
Venous drainage — the Achilles heel
- Tanaka & Tajima: relationship between venous outflow and viability is "all or nothing" — either no effect or complete congestive necrosis[3]
- Torii successful reverse-flow flaps drain via:
- Valve reflux at pressures 90–105 cmH₂O
- Communicating branches between venae comitantes
- Bypass vessels around valves[2]
- Scrotal venous return travels via anterior scrotal veins (to external pudendal → great saphenous) and posterior scrotal veins (to internal pudendal) — reverse-flow design must use retrograde anterior-scrotal-vein drainage or the venous anastomotic network
Choke-vessel conversion
- Choke anastomoses convert to true anastomoses through surgical delay or acute hemodynamic stress[5]
- Dilation begins immediately, peaks at 48–72 h, becomes permanent and irreversible by ~ 7 days[10]
- Mediated by HIF-1α, VEGF, iNOS upregulation[11]
- Explains the progressive improvement in retrograde perfusion in the early postoperative period[5][12]
Outcomes — Gao Case Report (n = 1)[1]
| Parameter | Result |
|---|---|
| Patient | 31-year-old male |
| Etiology | Complete penile skin loss 20 d after circumcision (infection + necrosis) |
| Procedure | Reverse bilateral anterior scrotal artery flap (single-stage) after debridement |
| Flap survival | Complete (100%) |
| Complications | None |
| Follow-up | 10 years — longest reported for any single scrotal-flap case |
| Erectile function | Normal |
| Sexual intercourse | Able to perform |
| Cosmesis | Satisfactory |
Advantages
- Bypasses a compromised proximal pedicle — the defining advantage. When the scrotal root or penoscrotal junction is scarred, infected, or surgically disrupted, antegrade flaps fail; reverse-flow design relies on the distal / posterior supply
- Single-stage
- No skin graft required
- Long-term durability — 10-year complication-free follow-up with preserved erection and intercourse
- Favorable vascular substrate — the "widely inter-anastomosed" scrotal network is more robust than typical extremity choke vessels
- Scrotal skin quality matches native shaft skin
Limitations and Disadvantages
- n = 1 evidence base — every conclusion about safety / efficacy is from a single patient
- Inherent reverse-flow risks — venous congestion is the dominant failure mode; in extremity series, Torii reported partial necrosis 18% and total necrosis 9% in reverse-flow island flaps[2]
- "All or nothing" venous drainage — when retrograde venous outflow fails, complete congestive necrosis can occur[3]
- Technically more demanding — requires understanding of reverse-flow hemodynamics, deliberate proximal-pedicle division, and meticulous preservation of distal anastomoses
- Dependence on intact posterior scrotal vasculature — any prior perineal surgery / radiation / trauma renders the technique unsafe
- No standardized PROMs
- Unknown complication profile at the population level
- Class-effect scrotal-flap morbidity — testicular ascension ~ 22.7%, late skin retraction ~ 27.3%, scrotal volume reduction (Mendel data)[14]
- No comparison with antegrade techniques — unclear whether reverse-flow offers any advantage in patients with intact proximal pedicles
Patient Selection — When Reverse-Flow Wins
Use this technique only in the specific clinical scenario where:
- The proximal scrotal root / penoscrotal junction is compromised (scarring, infection, prior surgery) — standard antegrade flaps cannot be based at the root
- Posterior scrotal vasculature is intact
- Circumferential penile coverage is required
- The surgeon is experienced with reverse-flow flap principles (retrograde hemodynamics, venous-congestion management, choke-vessel physiology)
For everything else, use an antegrade scrotal flap (Fakin, Murányi, Yao, Zhao) — larger evidence base and more predictable hemodynamics. The reverse-flow design is a salvage option when the proximal pedicle is unavailable.
Comparison Across All Major Scrotal-Flap Techniques
| Feature | Reverse (Gao) | Fakin | Murányi | Yao | Zhao total | Pribaz staged | VSSF |
|---|---|---|---|---|---|---|---|
| Flow direction | Retrograde | Antegrade | Antegrade | Antegrade | Antegrade | Neovascularization | Antegrade |
| Staging | Single | Single | Single | Single | Single | Two | Single |
| Evidence (n) | 1 | 43 | 49 | 7 | 18 | 8 | 15 |
| Flap survival | 100% | 100% | 90% | 100% | 100% | 100% | n/a |
| Follow-up | 10 y | 10.7 mo | n/r | n/r | 2.3 y | n/r | n/r |
| Unique advantage | Bypasses proximal pedicle | Largest series | Simplest technique | No pedicle tethering / length gain | Combined with elongation; sensation | Contaminated wounds | Outpatient |
| Primary limitation | n = 1 evidence | 9% partial necrosis | 6.7% ED | 28.6% partial necrosis | Large donor defect | Two operations | Ventral-only |
Key Takeaways
- The only published reverse-flow scrotal flap for penile reconstruction
- The defining and narrow indication is a compromised proximal scrotal pedicle — scarring / infection / prior surgery at the scrotal root that precludes standard antegrade techniques
- The "widely inter-anastomosed" scrotal substrate is a favorable reverse-flow substrate, but venous-congestion risk remains the dominant failure mode
- Level V evidence (single case) — every recommendation should be interpreted accordingly; broader adoption requires case-series validation
- For most clinical scenarios, antegrade scrotal flaps (Fakin / Murányi / Yao / Zhao) remain first-line
Cross-references
- Penile Reconstruction — full decision framework
- Bipedicled Anterior Scrotal Flap (Fakin)
- Modified Bipedicle Scrotal Tunnel Flap (Murányi)
- Modified Bilateral Butterfly Scrotal Flap (Yao)
- Total Anterior Scrotal Flap (Zhao)
- Staged Bipedicled Scrotal Flap (Pribaz / McLaughlin)
- Ventral Slit Scrotal Flap (VSSF)
- Foundations — Plastic Surgery Principles
References
1. Gao QG, Qu W. "Penile Resurfacing Using a Reverse Bilateral Anterior Scrotal Artery Flap: A Case Report of Penile Skin Defects Following Circumcision." Medicine. 2019;98(49):e18106. doi:10.1097/MD.0000000000018106
2. Torii S, Namiki Y, Mori R. "Reverse-Flow Island Flap: Clinical Report and Venous Drainage." Plast Reconstr Surg. 1987;79(4):600–9. doi:10.1097/00006534-198704000-00015
3. Tanaka Y, Tajima S. "The Influence of Arterial Inflow and Venous Outflow on the Survival of Reversed-Flow Island Flaps: An Experimental Study." Plast Reconstr Surg. 1997;99(7):2021–9. doi:10.1097/00006534-199706000-00031
4. Carrera A, Gil-Vernet A, Forcada P, et al. "Arteries of the Scrotum: A Microvascular Study and Its Application to Urethral Reconstruction With Scrotal Flaps." BJU Int. 2009;103(6):820–4. doi:10.1111/j.1464-410X.2008.08167.x
5. Taylor GI, Corlett RJ, Ashton MW. "The Functional Angiosome: Clinical Implications of the Anatomical Concept." Plast Reconstr Surg. 2017;140(4):721–733. doi:10.1097/PRS.0000000000003694
6. Giraldo F, Mora MJ, Solano A, González C, Smith-Fernández V. "Male Perineogenital Anatomy and Clinical Applications in Genital Reconstructions and Male-to-Female Sex Reassignment Surgery." Plast Reconstr Surg. 2002;109(4):1301–10. doi:10.1097/00006534-200204010-00014
7. Fakin R, Zimmermann S, Jindarak S, et al. "Reconstruction of Penile Shaft Defects Following Silicone Injection by Bipedicled Anterior Scrotal Flap." J Urol. 2017;197(4):1166–1170. doi:10.1016/j.juro.2016.11.093
8. Yao H, Zheng D, Xie M, et al. "A Modified Bilateral Scrotal Flap for Penile Skin Defect Repair." J Vis Exp. 2022;(189). doi:10.3791/64017
9. Murányi M, Varga D, Kiss Z, Flaskó T. "A New Modified Bipedicle Scrotal Skin Flap Technique for the Reconstruction of Penile Skin in Patients With Paraffin-Induced Sclerosing Lipogranuloma of the Penis." J Urol. 2022;208(1):171–178. doi:10.1097/JU.0000000000002480
10. Dhar SC, Taylor GI. "The Delay Phenomenon: The Story Unfolds." Plast Reconstr Surg. 1999;104(7):2079–91. doi:10.1097/00006534-199912000-00021
11. Luo Z, Wu P, Qing L, et al. "The Hemodynamic and Molecular Mechanism Study on the Choke Vessels in the Multi-Territory Perforator Flap Transforming Into True Anastomosis." Gene. 2019;687:99–108. doi:10.1016/j.gene.2018.11.019
12. Ji J, Chen D, Ni J, Chang F. "Research Advances in Vascular Remodeling in Choke Vessels of Perforator Flap: A Systematic Review." Ann Plast Surg. 2024;93(2):268–275. doi:10.1097/SAP.0000000000003980
13. Kristinsson S, Johnson M, Ralph D. "Review of Penile Reconstructive Techniques." Int J Impot Res. 2021;33(3):243–250. doi:10.1038/s41443-020-0246-4
14. Mendel L, Neuville P, Allepot K, et al. "Bilateral Pedicled Scrotal Flaps as an Alternative to Skin Graft in Penile Shaft Defects Repair." Urology. 2023;176:206–212. doi:10.1016/j.urology.2023.03.025
15. McLaughlin MM, Abbassi B, Pribaz JJ. "Bipedicled Scrotal Flap for Penile Resurfacing." Plast Reconstr Surg. 2024;153(4):935–942. doi:10.1097/PRS.0000000000010811
16. Zhao YQ, Zhang J, Yu MS, Long DC. "Functional Restoration of Penis With Partial Defect by Scrotal Skin Flap." J Urol. 2009;182(5):2358–61. doi:10.1016/j.juro.2009.07.048
17. Westerman ME, Tausch TJ, Zhao LC, et al. "Ventral Slit Scrotal Flap: A New Outpatient Surgical Option for Reconstruction of Adult Buried Penis Syndrome." Urology. 2015;85(6):1501–4. doi:10.1016/j.urology.2015.02.030