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Singapore Flap Urethroplasty

The Singapore flap, also known as the pudendal thigh fasciocutaneous flap (PTF), is a sensate fasciocutaneous flap from the labiocrural or groin-crease fold. Wee and Joseph first described it in 1989 for vaginal reconstruction.[1] It is related to, but not synonymous with, the broader internal pudendal artery perforator (IPAP) flap family. Its use in urethroplasty extends a perineal reconstructive flap. The urological experience consists of a case report, a mixed-indication flap series, one phalloplasty cohort and a chapter-reported single-surgeon series.[2][3][4][6]

For flap anatomy and broader applications, see Singapore / Pudendal Thigh Flap in foundations.

For the gluteal-fold variant used predominantly for vulvar oncologic and male perineal / scrotal reconstruction, see Lotus Petal Flap. For the urethroplasty alternative when local penile and perineal options are exhausted, see Propeller Flap Urethroplasty.

Published Urological Applications​

1. Tzarnas 1994 — first reported urethroplasty use​

The earliest reported urological application of the pudendal thigh fasciocutaneous flap was for a traumatic posterior urethral stricture after vaginoplasty (gender-affirming surgery). The anatomic constraints of the reassigned perineum precluded standard urethroplasty options, and the pudendal thigh flap was used to bridge the defect. The stricture was successfully corrected with an inconspicuous donor-site scar.[2]

2. Monstrey 2001 — posterior urethral defects in a scarred perineum​

Monstrey reported a mixed-indication series of 31 pudendal thigh flaps (vaginal reconstruction for atresia or after oncological resection, rectovaginal fistula and urethral defects). Two patients had posterior urethral defects in a heavily scarred perineum.[3] All 31 flaps survived completely and functional outcome was reported as excellent in all patients. Some hair growth was present in the flaps, a recognized concern when fasciocutaneous tissue lines the urethra.

3. Wu 2022 — neourethral reconstruction in pedicled ALT phalloplasty​

Wu reported 49 patients receiving pedicled ALT penile reconstruction for micropenis, trauma or iatrogenic defects. Eleven were listed as receiving a pudendal-thigh neourethra.[4]

The abstract reports urethral complications (flap necrosis, urinary fistula, stricture) in 38.5% of the pudendal-thigh subgroup, a figure that is not a whole-number fraction of 11, so the exact subgroup rate is uncertain. Techniques were selected according to patient characteristics. All patients voided standing after revision procedures.[4]

4. Zinman — configuration, transfer technique and chapter-reported experience​

Leonard Zinman described urethral applications of the perineal-artery (Singapore) fasciocutaneous flap, originally described by Wee and Joseph for vaginal reconstruction.[1] In his chapter, a ventral transverse island onlay is the most common urethral configuration when a usable urethral roof remains.[6] He reserves tube interposition for selected long post-traumatic gaps that cannot be bridged by standard anastomosis, particularly with anterior urethral vascular compromise or prior surgery, and describes first-stage flap marsupialization, as proximal urethrostomy with perineal wound cover, for recurrent or radiated bulbomembranous strictures with extensive fibrosis and inadequate local skin, deferring definitive reconstruction until the urethral openings are stable.[6]

For selected proximal bulbomembranous or prostatomembranous strictures after prior failed repair or radiation, Zinman describes a ventral onlay repair: retrograde bougienage marks the distal stricture limit, a #5 Fogarty balloon inflated with 1 mL saline marks the proximal limit, and an indwelling 24 Fr catheter sizes the proximal urethrotomy.[6] His medial-thigh skin/fascia flap measures 15 × 6 cm and carries a distal transverse island 6–8 cm long and 2 cm wide; two of seven onlay patients also received a buccal mucosa graft.[5][6] In Zinman's onlay technique, the flap includes deep fascia and adductor epimysium; he fixes fascia to dermis to protect segmental vessels, checks distal-edge bleeding, and de-epithelializes a proximal strip while retaining a thin layer of dermis to protect the transverse island. He divides the tissue bridge between the flap base and urethral exposure rather than tunneling, avoiding pedicle compression, easing transfer of the distal island to the proximal urethra, and reducing donor-site closure tension.[6]

He reports a chapter series of 13 patients treated from 1992 onward, with proximal bulbomembranous or prostatomembranous disease, stricture lengths of 3–12 cm and follow-up of 1–10 years: seven received an onlay island patch (two combined with a buccal graft), four had one-stage tube interposition for post-traumatic 6–8 cm gaps, and two had first-stage procedures. One of the four tube-interposition patients developed recurrent stenosis and underwent marsupialization without completing a second-stage reconstruction.[6] Reported complications included two transient anterior compartment syndromes, two donor-site infections requiring drainage and antibiotics, and one hematoma without skin-island loss; no fistulas or diverticula were reported. Limit time in high lithotomy where feasible: a separate mixed urethroplasty cohort associated longer high-lithotomy duration with lower-extremity complications.[8] The chapter defines no overall success rate.[6]

Why a Singapore Flap for Urethroplasty​

When local penile and perineal tissue is exhausted, scarred, or anatomically reorganized (post-GAS, post-pelvic-trauma, post-radiation), the Singapore flap brings several urethroplasty-relevant advantages:

  • Sensate. The flap retains cutaneous innervation from the perineal nerves, important for genital reconstruction.[1][3]
  • Tissue from outside the immediate zone of injury. A groin or labiocrural donor may lie outside the scarred urethral bed, but prior surgery or radiation at that site must be assessed; Zinman checks distal-edge bleeding before transfer.[2][3][6]
  • Superficial perineal arterial supply comes from the internal pudendal system. All 31 flaps survived in Monstrey's mixed-indication series.[3]
  • Thin and pliable. The flap adapts to perineal urethral and neourethral defects without excessive bulk.
  • Primary donor-site closure leaves the scar in the natural groin fold.[3]

Limitations Specific to Urethroplasty​

  • Hair-bearing skin. Inspect proposed luminal skin for hair before harvest. Monstrey reported hair growth in these flaps.[3] Intraluminal hair can form hairballs, contribute to calculi and cause chronic infection; the 2026 EAU guideline recommends against hair-bearing perineal or scrotal flaps unless no other option is feasible .[7]
  • Posterior or perineal urethral defects are the best fit. The arc of rotation and flap dimensions limit anterior reach, so long anterior penile strictures are poorly served.
  • No comparative data versus BMG or penile fasciocutaneous flaps exist for urethroplasty.
  • Small, heterogeneous cohorts.
  • Three-territory vascular anatomy. Larger flaps may have a precarious apex. For technical mitigation (delay procedure, IPAP perforator-based design), see the foundations Singapore flap page.

Where It Fits in the Urethroplasty Algorithm​

The Singapore flap is a selected salvage option rather than a primary urethroplasty option. For urethral tissue transfer generally, EAU 2026 recommends a graft when graft and flap are equally indicated , and a flap for a poorly vascularized urethral bed .[7] The AUA 2023 guideline notes that a tubularized flap may be used when no alternative exists, with inferior results to an onlay flap.[7][10] It is used for:

  • Posterior urethral defects in a scarred or anatomically altered perineum when local rotation flaps are not available, including post-GAS strictures.[2][3]
  • Neourethral reconstruction within pedicled ALT penile reconstruction when anatomy and reconstructive needs favor separate urethral tissue.[4]
  • Salvage scenarios with concurrent perineal soft-tissue defects requiring resurfacing alongside urethral reconstruction.

For radiation-associated bulbomembranous strictures, assess bladder function and baseline continence when selecting reconstruction. EAU 2026 recommends counseling about de novo incontinence and new erectile dysfunction after urethroplasty .[9]

For operative options, see Distal Penile Circular Fasciocutaneous Flap (McAninch), Buccal Mucosa Graft, and the Master Decision Framework.

Videos​

Markings and Design for a Singapore Flap
Masterclass in Obstetric Fistula

References​

1. Wee JT, Joseph VT. A new technique of vaginal reconstruction using neurovascular pudendal-thigh flaps: a preliminary report. Plast Reconstr Surg. 1989;83(4):701-709. doi:10.1097/00006534-198904000-00018.

2. Tzarnas CD, Raezer DM, Castillo OA. A unique fasciocutaneous flap for posterior urethral repair. Urology. 1994;43(3):379-381. doi:10.1016/0090-4295(94)90084-1.

3. Monstrey S, Blondeel P, Van Landuyt K, et al. The versatility of the pudendal thigh fasciocutaneous flap used as an island flap. Plast Reconstr Surg. 2001;107(3):719-725. doi:10.1097/00006534-200103000-00011.

4. Wu Q, Yang Z, Ma N, Wang W, Li Y. Urethra reconstruction and revision urethroplasty in pedicled anterolateral thigh flap penile reconstruction. Ann Plast Surg. 2022;89(2):201-206. doi:10.1097/SAP.0000000000003100.

5. Zinman LN. Combined Use of Fasciocutaneous, Muscular and Myocutaneous Flaps and Graft Onlays in Urethral Reconstruction. In: Montague DK, Gill IS, Angermeier KW, Ross JH, eds. Textbook of Reconstructive Urologic Surgery. Informa Healthcare; 2008:487–502.

6. Zinman L. Selective Use of the Perineal Artery Fasciocutaneous Flap (Singapore) in Urethral Reconstruction. In: Schreiter F, Jordan GH, eds. Urethral Reconstructive Surgery. Springer; 2006:153–160. doi:10.1007/3-540-29385-x_19

7. European Association of Urology. "EAU Guidelines on Urethral Strictures: Tissue Transfer." 2026. Guideline

8. Anema JG, Morey AF, McAninch JW, Mario LA, Wessells H. "Complications related to the high lithotomy position during urethral reconstruction." J Urol. 2000;164(2):360-363. doi:10.1016/S0022-5347(05)67360-0

9. European Association of Urology. "EAU Guidelines on Urethral Strictures: Disease Management in Males." 2026. Guideline

10. Wessells H, Morey A, Souter L, Rahimi L, Vanni A. "Urethral stricture disease guideline amendment (2023)." J Urol. 2023;210(1):64–71. doi:10.1097/JU.0000000000003482