Internal Pudendal Artery Perforator (IPAP) Flap
The IPAP flap is a free-style pedicled perforator flap based on skin perforators from the internal pudendal artery, formally described by Hashimoto et al. (2014). It is the modern perforator-based evolution of the pudendal-thigh (Singapore), lotus petal, and gluteal-fold flaps — and is now a workhorse in perineal soft-tissue reconstruction. The original series demonstrated no total flap failures in 71 flaps (45 patients) across vulvar, vaginal, buttock, anal, and pelvic-cavity reconstruction.[1][2]
For the genital-context treatment menu see the Vulvar Reconstruction Atlas and Scrotal Reconstruction Techniques. For related parent / sibling flaps see Lotus Petal, Singapore / pudendal-thigh, IGAP / Gluteal-Fold, EPAP, and MCFAP. For the broader perforator-flap framework see SCIP / perforator flap.
Historical Development
The IPAP flap sits at the apex of an evolutionary lineage of perineal flaps sharing the same vascular territory:[2]
| Year | Contribution |
|---|---|
| 1996 — Yii & Niranjan | Lotus petal flap — first recognition of the perineal perforator territory as a distinct flap source |
| 2001 — Hashimoto et al. | Cadaveric study of the gluteal-fold flap — blood supply is a direct cutaneous system of the IPA and vein, enabling safe flap thinning[3] |
| 2001 — Hashimoto | 3–5 perforators in the perineal anogenital triangle[2] |
| 2009 — Jin et al. | Microdissection (22 sides / 11 cadavers) identifying 4 relatively constant perineal perforators[4] |
| 2014 — Hashimoto et al. | Formal IPAP description — free-style pedicle perforator flap with propeller / transposition / V-Y advancement movements[1] |
| 2021 — Giroux et al. | Routine preoperative ultrasound not always required[2] |
The IPAP is distinguished by its free-style, perforator-based approach — designed around Doppler-identified perforators rather than a fixed anatomic template.[2]
Vascular Anatomy
Perforator anatomy (Hashimoto 2001; Giroux 2021)[1][2]
- 3–5 perforators consistently present in the perineal anogenital triangle.
- Ischial tuberosity is the key landmark and safe boundary of medial dissection.
- Mean distance from ischial tuberosity to perforator: 27.3 mm (Giroux Doppler study of 15 subjects, 24 perforators > 5 mm).
- Perforator positions measured by orthonormal landmarks (distance from midline + inter-ischial-tuberosity line).
Source artery — internal pudendal artery
The IPA is a terminal branch of the anterior division of the internal iliac artery. Relevant branches:[3][4][5]
- Posterior labial (scrotal) aa. — terminal branches of the superficial perineal a. (continuation of the IPA); run deep to Colles' fascia close to the midline.
- Direct cutaneous perforators — emerge through the ischiorectal fossa fat to supply the overlying gluteal-fold / perineal skin.
- Lateral branch of the posterior labial a. — contributes a perforating branch to the lower vascular anastomosis.
Microdissection — Jin 2009[4]
Four relatively constant perineal perforators — inguinal and perineal branches of the superficial external pudendal a., obturator anterior cutaneous branch, and lateral branch of the posterior labial (pudendal) a. — all direct perforators forming upper, middle, and lower deep-fascial anastomoses above the adductor wall.
Three-territory concept — Tham 2010[5]
| Territory | Source | Plane |
|---|---|---|
| 1 (medial / base) | Posterior labial aa. | Deep to Colles' fascia |
| 2 (middle) | Obturator a. cutaneous branches | Superficial to Colles' fascia |
| 3 (lateral / apex) | External pudendal a. branches | Superficial to Colles' fascia |
Pedicle is close to the midline — lateral / apical portions of large flaps have a precarious blood supply.
Sensory innervation
- Pudendal nerve branches — primary sensory supply.[6]
- Posterior femoral cutaneous nerve — gluteal-fold territory.[6]
- Flap retains cutaneous innervation — sensate reconstruction.[6]
Indications
| Category | Application |
|---|---|
| Vulvar | Hemivulvectomy / radical vulvectomy (36/45 in Hashimoto); SCC / EMPD / melanoma[1][9] |
| Vaginal | Partial / circumferential vaginal defects (9/45 in Hashimoto)[1] |
| Perineal | APR / ELAPE — proposed as first choice for moderate / some large defects (Coltro); pelvic exenteration (6/45 in Hashimoto)[1][7][10] |
| Anal | Anal defects after oncological resection (6/45 in Hashimoto)[1] |
| Buttock | Buttock skin defects (10/45 in Hashimoto); ischial pressure sores (PIPAP)[1][11] |
| Other | Fournier's gangrene peri-vulvar reconstruction;[8] penoscrotal IPAP propeller from the gluteal fold;[12] chronic perineal wounds / sinuses[10] |
Surgical Technique (Hashimoto 2014)[1]
- Position — lithotomy (vulvar / vaginal / anal / pelvic cavity) or prone (buttock).
- Perforator identification — handheld Doppler on / around the ischiorectal fossa; arterial sounds mark the flap base.
- Flap design — free-style; skin island centered on the identified perforator(s):
- Propeller flap — most common (35/45 cases); rotated 90–180° around the perforator pivot point.
- V-Y advancement — 7/45 cases; advanced on the perforator pedicle.
- Traditional transposition — 3/45 cases.
- Incision and elevation — circumferential incision; suprafascial elevation preserving the perforator as the sole supply.
- Flap thinning — performed in all cases except pelvic-cavity reconstruction; adipose tissue removed except the tissue around the pedicle vessels — a key advantage over traditional designs.[1]
- Transfer — rotated (propeller), advanced (V-Y), or transposed depending on the design.
- Donor closure — primary, scar concealed in the gluteal fold or perineal crease.
Key technical points:
- Ischial tuberosity is the safe boundary of medial dissection.[2]
- Routine preoperative ultrasound is not always required — Giroux showed perforator positions are predictable enough to allow harvesting without imaging.[2]
- Provides suitable volume for both thin reconstructions (vulvar, vaginal, anal) and bulky reconstructions (pelvic-cavity dead-space obliteration).[1]
Variants and Modifications
| Variant | Author / year | Concept |
|---|---|---|
| IPAT (Internal Pudendal Artery Turnover) | Nassar 2021[13] | Turnover flap requiring no perforator visualization / dissection; raised on reliable IPA vasculature and de-epithelialized to fill deep 3D defects. n = 38 — no flap or partial losses; 10/38 complications (9 minor, 1 return to theatre) |
| Perineal Turnover Perforator (PTO) | Chasapi 2018[14] | IPA-perforator-based turnover flap; thick gluteal dermis as autologous dermal vascularized substitute for excised pelvic-floor muscles + subcutaneous bulk to obliterate dead space. n = 14 ELAPE; no flap / donor / major wound complications; median OR 49 min |
| Bilobed pudendal artery perforator flap | Yun 2010[15] | Bilobed design — improved arc of rotation and mobility for wide / deep defects; preserves distinct urogenital and anal-triangle tissue. n = 15 (7 vulvar SCC, 7 EMPD, 1 RVF); 100% flap survival; 3 × 4 to 13 × 12 cm |
| Gull-wing flap | Han 2016[16] | IPA-perforator-based gull-wing flap for 3D vulvovaginal reconstruction; perforator = pivot, rotated > 150–180° internally; reconstructs labium and external vaginal wall with sufficient volume |
| PIPAP for ischial pressure sores | Legemate 2018[11] | Skin flap along the gluteal fold; perforators marked by Doppler medially in the gluteal fold; suprafascial elevation. n = 27 / 34 flaps; mean OR 60 ± 21 min; minor complications 6/34 (9%); 9/34 (27%) required a second procedure (3 for recurrent ulcers) |
| IPAP propeller for penoscrotal reconstruction | Han 2018[12] | IPAP propeller from the gluteal fold rotated > 90° tension-free; long axis centered on the gluteal fold. n = 10; mean flap 6.7 × 11.7 cm; partial distal necrosis in 1 (healed spontaneously); all patients satisfied |
| Rotation / island / propeller variants | Loreti 2023[17] | n = 11 APR perineal reconstructions — rotation (8), island advancement (2), propeller (1). 100% flap survival; no immediate major complications; LOS 11 d; reliable in irradiated tissues (8/11) |
Outcomes
| Study | n / flaps | Indication | Flap survival | Complications | Headline |
|---|---|---|---|---|---|
| Hashimoto 2014[1] | 45 pts / 71 flaps | Vulvar (36) / buttock (10) / vagina (9) / anus (6) / pelvic cavity (6) | 94.4% complete; 0% total loss | 4 partial necrosis; 1 debulking | Original IPAP; propeller most common; thinning in all except pelvic cavity |
| Coltro 2015 (sensibility)[6] | 25 pts (bilateral V-Y IPAP) | Perineal (APER) | High | — | Sensibility maintained at 12 mo; no significant difference vs preoperative |
| Coltro 2017 (irradiated APR)[7] | 73 pts / 122 flaps | Perineal (irradiated APR) | 95% healed at 12 wk | CD III–IV higher if defect ≥ 60 cm² (p = 0.03; OR 10.56) | Largest IPAP series for APR; proposed as first-choice for moderate / large defects |
| Yun 2010[15] | 15 | Vulvar SCC (7) / EMPD (7) / RVF (1) | 100% | None | Bilobed; improved arc of rotation |
| Han 2016[16] | Case series | Vulvovaginal | High | No serious complications | Gull-wing flap; 3D vulvovaginal reconstruction |
| Baek 2017[8] | Case series | Fournier's gangrene (female) | High | — | IPAP ideal for peri-vulvar reconstruction after necrotizing fasciitis |
| Legemate 2018 (PIPAP)[11] | 27 pts / 34 flaps | Ischial pressure sores | High | Minor 9%; major 27% (incl. recurrent ulcers) | PIPAP variant; mean OR 60 min; median follow-up 38 mo |
| Chasapi 2018 (PTO)[14] | 14 | Perineal (ELAPE) | 100% | 1 superficial dehiscence; 1 perineal hernia | PTO flap; median OR 49 min; no chronic perineal pain |
| Nassar 2021 (IPAT)[13] | 38 | Perineal (APR / exenteration / pilonidal) | 100% (no flap or partial loss) | 10/38 (9 minor, 1 return to theatre) | IPAT flap; no perforator dissection required; quick and reliable |
| Han 2023[9] | 47 (31 IPAP / 16 PAP-TUG) | Vulvar (EMPD / SCC / other) | High | IPAP 12.9% vs PAP-TUG 37.5% (p = 0.04) | IPAP significantly fewer wound complications than PAP / TUG |
| Loreti 2023[17] | 11 | Perineal (APR) | 100% | 1 donor-site dehiscence | Reliable even in irradiated tissues (8/11) |
| Han 2018 (penoscrotal)[12] | 10 | Penoscrotal | High | 1 partial distal necrosis | IPAP propeller from gluteal fold; all patients satisfied |
Sensibility — Coltro 2015[6]
The only prospective study specifically evaluating IPAP cutaneous sensibility:
- 25 patients undergoing APER with bilateral V-Y advancement IPAP flap reconstruction.
- Sensibility assessed at 4 areas of the gluteal fold preoperatively and at the corresponding 4 flap areas 12 mo postoperatively.
- Tactile (PSSD™): no significant difference between preoperative and postoperative (p > 0.05 in all 4 areas).
- Pain, thermal, vibration: 100% preserved in all 4 areas postoperatively.
Cutaneous sensibility is expected to be maintained — attributed to pudendal-nerve + PFCN innervation preserved during elevation.
Comparison with Other Flaps
IPAP vs PAP / TUG for vulvar reconstruction (Han 2023, n = 47)[9]
| Parameter | IPAP (n = 31) | PAP / TUG (n = 16) | p |
|---|---|---|---|
| Wound complications | 12.9% | 37.5% | 0.04 |
| Functional complications | Similar | Similar | NS |
| 2-y oncologic recurrence | 14.9% (overall) | No significant difference | NS |
Han et al. proposed an algorithm using the vulvo-thigh junctional crease (inferior pubic ramus) as the decision point — defects medial → IPAP; defects lateral → PAP / TUG.
Lotus petal vs V-Y (Confalonieri 2017, n = 284)[18]
| Parameter | Lotus petal (n = 128) | V-Y (n = 234) | p |
|---|---|---|---|
| Overall complications | 13% | 21% | 0.588 (NS) |
| Tunneled LPF | Superior functional / cosmetic results for primary malignancies | — | — |
IPAP vs primary closure for APR (Coltro 2017)[7]
IPAP proposed as a step forward over primary closure — 95% complete wound healing at 12 wk even in irradiated patients; proposed as first choice for moderate / some large defects after APR.
IPAP vs VRAM / gracilis[1][7][14][19]
| Advantage | IPAP |
|---|---|
| Muscle sacrifice | No (vs gracilis / VRAM) |
| Patient repositioning | Not required (lithotomy) |
| Operative time | Shorter — IPAT 49 min, PIPAP 60 min |
| Volume adjustability | Thinned for vulvar / vaginal / anal; full-thickness for pelvic cavity |
| Donor-site morbidity | Lower (no abdominal-wall weakness or thigh weakness) |
For very large defects with extensive pelvic dead space, musculocutaneous flaps may still be preferred.[19]
Risk Factors for Complications (Coltro 2017, n = 73 / 122 flaps APR)[7]
- Higher BMI → longer healing time (p = 0.02).
- Defect ≥ 60 cm² → Clavien-Dindo III–IV (p = 0.03; OR 10.56).
- Anal SCC → higher postoperative complications (p = 0.005; OR 6.09).
- Comorbidities → higher postoperative complications (p = 0.04; OR 2.78).
- Postoperative complications → longer LOS (p = 0.001) and healing time (p < 0.001).
Position in Reconstructive Algorithms
| Algorithm | Position |
|---|---|
| Han 2023[9] | Vulvo-thigh junctional crease as decision point — medial → IPAP; lateral → PAP / TUG; Doppler-confirmed perforator |
| Negosanti 2015[19] | Type IA → monolateral lotus petal; Type IB → bilateral lotus petal; Type II → pedicled DIEP |
| Toulouse 2025 | Perforator flaps first-line; IPAP preferred for posterior and lateral vulvar defects |
| Höckel 2008[20] | Lotus-petal / gluteal-fold / Singapore flaps (IPAP predecessors) — pudendal-thigh for lateral / hemivulvectomy (unilateral) and total vulvar (bilateral) |
Advantages
| Advantage | Detail |
|---|---|
| Free-style design flexibility | Propeller / V-Y / transposition / turnover around Doppler-identified perforators[1] |
| Adjustable volume | Thinned for vulvar / vaginal / anal; full-thickness for pelvic-cavity dead-space obliteration[1] |
| Sensate | Pudendal + PFCN branches; all 4 sensory modalities maintained at 12 mo[6] |
| No total flap failures | 0% total loss across Hashimoto / Coltro / Nassar / Loreti[1][7][13][17] |
| Fewer wound complications than PAP / TUG | 12.9% vs 37.5% (p = 0.04)[9] |
| Reliable in irradiated tissues | Loreti 100% in 8/11 irradiated; Coltro 95% healing at 12 wk in irradiated APR[7][17] |
| No preoperative imaging required | Giroux — perforator positions predictable[2] |
| No muscle sacrifice | Fasciocutaneous / perforator design[1] |
| No patient repositioning | Lithotomy for vulvar / vaginal / anal / pelvic[1] |
| Concealed donor scar | Hidden in the gluteal fold or perineal crease[1][11] |
| Primary donor closure | All donor sites closed primarily[1] |
| Quick operative time | IPAT ~49 min; PIPAP ~60 min[11][14] |
| Versatile | Vulvar / vaginal / anal / buttock / pelvic-cavity / penoscrotal / pressure sore[1][7][11][12] |
Limitations
| Limitation | Detail |
|---|---|
| Partial necrosis | 4/71 (5.6%) in Hashimoto; no total failures[1] |
| Large defects with extensive pelvic dead space | Musculocutaneous (VRAM / gracilis) may still be required[19] |
| Defect ≥ 60 cm² | Significantly higher Clavien-Dindo III–IV complications[7] |
| Higher BMI | Longer healing time[7] |
| Anal SCC histology | Higher postoperative complications[7] |
| Learning curve | Doppler perforator identification and perforator-based design — though IPAT variant eliminates perforator dissection[13] |
| Bulkiness in obese patients | Thinning is possible but requires familiarity with the vascular anatomy[3] |
| Limited arc of rotation | Common-sheath / nerve-loop IGA-descending-branch / PFCN topology can constrain propeller rotation |
| 30-day mortality 4% in Coltro APR | Related to the oncological procedure, not the flap itself[7] |
| Hair-bearing skin | May cause chronic discharge / dissatisfaction when used for vaginal reconstruction |
Relationship to Other Perineal Perforator Flaps
| Feature | IPAP (Hashimoto 2014) | Lotus petal (Yii 1996) | Pudendal-thigh / Singapore (Wee 1989) | Gluteal-fold (Hashimoto 2001) |
|---|---|---|---|---|
| Design philosophy | Free-style perforator | Fasciocutaneous transposition | Axial-pattern fasciocutaneous | Fasciocutaneous island |
| Perforator identification | Handheld Doppler | Not required | Not required | Not required |
| Flap movement | Propeller / V-Y / transposition | Transposition | Transposition / rotation | Transposition / V-Y |
| Thinning | Routine (all except pelvic cavity) | Possible | Limited (two-stage liposuction) | Possible (Hashimoto technique) |
| Fascial plane | Suprafascial (perforator-based) | Subfascial or suprafascial | Subfascial (incl. deep fascia + epimysium) | Subfascial |
| Primary indication | All perineal defects | Vulvoperineal | Vaginal reconstruction | Vulvar / buttock |
The evolution Singapore (1989) → lotus petal (1996) → gluteal fold (2001) → IPAP (2014) represents a progression from territory-based axial flap to free-style perforator flap — enabling greater design flexibility, routine thinning, and more versatile movement patterns while maintaining the same reliable IPA territory.[2]
Key Takeaways
- The IPAP flap (Hashimoto 2014) is a free-style pedicled perforator flap on IPA skin perforators identified by handheld Doppler on / around the ischiorectal fossa.[1]
- Modern perforator-based evolution of the Singapore / lotus petal / gluteal-fold flaps — same IPA vascular territory, free-style design.[2]
- 0% total flap failures across all major series; partial necrosis 5.6%.[1]
- Cutaneous sensibility maintained at 12 mo — all 4 modalities show no significant difference from preoperative values.[6]
- Significantly fewer wound complications than PAP / TUG (12.9% vs 37.5%, p = 0.04); Han 2023 vulvo-thigh-crease algorithm.[9]
- Reliable even in irradiated tissues — 95% healing at 12 wk after irradiated APR; 100% survival in 8/11 irradiated Loreti patients.[7][17]
- Adjustable-volume design — thinned for vulvar / vaginal / anal; full-thickness for pelvic-cavity dead-space obliteration.[1]
- Toulouse 2025 algorithm — perforator flaps first-line; IPAP preferred for posterior and lateral vulvar defects.
References
1. Hashimoto I, Abe Y, Nakanishi H. The internal pudendal artery perforator flap: free-style pedicle perforator flaps for vulva, vagina, and buttock reconstruction. Plast Reconstr Surg. 2014;133(4):924–933. doi:10.1097/PRS.0000000000000008
2. Giroux PA, Dast S, Assaf N, Lari A, Sinna R. Internal pudendal perforator artery flap harvesting without pre-operative imaging: reliability and approach. J Plast Reconstr Aesthet Surg. 2021;74(6):1355–1401. doi:10.1016/j.bjps.2020.12.017
3. Hashimoto I, Nakanishi H, Nagae H, Harada H, Sedo H. The gluteal-fold flap for vulvar and buttock reconstruction: anatomic study and adjustment of flap volume. Plast Reconstr Surg. 2001;108(7):1998–2005. doi:10.1097/00006534-200112000-00025
4. Jin B, Hasi W, Yang C, Song J. A microdissection study of perforating vessels in the perineum: implication in designing perforator flaps. Ann Plast Surg. 2009;63(6):665–669. doi:10.1097/SAP.0b013e3181999de3
5. Tham NL, Pan WR, Rozen WM, et al. The pudendal thigh flap for vaginal reconstruction: optimising flap survival. J Plast Reconstr Aesthet Surg. 2010;63(5):826–831. doi:10.1016/j.bjps.2009.02.060
6. Coltro PS, Ferreira MC, Busnardo FF, et al. Evaluation of cutaneous sensibility of the internal pudendal artery perforator (IPAP) flap after perineal reconstructions. J Plast Reconstr Aesthet Surg. 2015;68(2):252–261. doi:10.1016/j.bjps.2014.09.049
7. Coltro PS, Busnardo FF, Mônaco Filho FC, et al. Outcomes of immediate internal pudendal artery perforator flap reconstruction for irradiated abdominoperineal resection defects. Dis Colon Rectum. 2017;60(9):945–953. doi:10.1097/DCR.0000000000000875
8. Baek SO, Park SH, Rhie JW, Han HH. Peri-vulvar reconstruction using internal pudendal artery perforator flap in female Fournier's gangrene. Int Wound J. 2017;14(6):1378–1381. doi:10.1111/iwj.12744
9. Han WY, Kim Y, Han HH. A simplified algorithmic approach to vulvar reconstruction according to various types of vulvar defects. Ann Plast Surg. 2023;91(2):270–276. doi:10.1097/SAP.0000000000003597
10. Nassar MK, Jordan DJ, Quaba O. The internal pudendal artery turnover (IPAT) flap: a new, simple and reliable technique for perineal reconstruction. J Plast Reconstr Aesthet Surg. 2021;74(9):2104–2109. doi:10.1016/j.bjps.2020.12.074
11. Legemate CM, van der Kwaak M, Gobets D, Huikeshoven M, van Zuijlen PPM. The pedicled internal pudendal artery perforator (PIPAP) flap for ischial pressure sore reconstruction: technique and long-term outcome of a cohort study. J Plast Reconstr Aesthet Surg. 2018;71(6):889–894. doi:10.1016/j.bjps.2018.01.032
12. Han SE, Kim EJ, Sung HH, Pyon JK. Aesthetic penoscrotal resurfacing: creating propeller flaps from gluteal folds. Eur Urol. 2018;73(4):610–617. doi:10.1016/j.eururo.2016.09.033
13. Nassar MK, Jordan DJ, Quaba O. The internal pudendal artery turnover (IPAT) flap: a new, simple and reliable technique for perineal reconstruction. J Plast Reconstr Aesthet Surg. 2021;74(9):2104–2109. doi:10.1016/j.bjps.2020.12.074
14. Chasapi M, Maher M, Mitchell P, Dalal M. The perineal turnover perforator flap: a new and simple technique for perineal reconstruction after extralevator abdominoperineal excision. Ann Plast Surg. 2018;80(4):395–399. doi:10.1097/SAP.0000000000001267
15. Yun IS, Lee JH, Rah DK, Lee WJ. Perineal reconstruction using a bilobed pudendal artery perforator flap. Gynecol Oncol. 2010;118(3):313–316. doi:10.1016/j.ygyno.2010.05.007
16. Han HH, Jun D, Seo BF, et al. Internal pudendal perforator artery-based gull wing flap for vulvovaginal 3D reconstruction after tumour excision: a new flap. Int Wound J. 2016;13(5):920–926. doi:10.1111/iwj.12410
17. Loreti A, Arelli F, Spallone D, Bruno E, Abate O. The use of the internal pudendal artery perforator flap after abdominoperineal reconstruction: a single center study. J Plast Reconstr Aesthet Surg. 2023;84:87–92. doi:10.1016/j.bjps.2023.05.015
18. Confalonieri PL, Gilardi R, Rovati LC, et al. Comparison of V-Y advancement flap versus lotus petal flap for plastic reconstruction after surgery in case of vulvar malignancies: a retrospective single center experience. Ann Plast Surg. 2017;79(2):186–191. doi:10.1097/SAP.0000000000001094
19. Negosanti L, Sgarzani R, Fabbri E, et al. Vulvar reconstruction by perforator flaps: algorithm for flap choice based on the topography of the defect. Int J Gynecol Cancer. 2015;25(7):1322–1327. doi:10.1097/IGC.0000000000000481
20. Höckel M, Dornhöfer N. Vulvovaginal reconstruction for neoplastic disease. Lancet Oncol. 2008;9(6):559–568. doi:10.1016/S1470-2045(08)70147-5