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The Perineum

The perineum is the diamond-shaped region of the pelvic outlet below the pelvic diaphragm. It is the operative field for bulbar urethroplasty, radical perineal prostatectomy, AUS placement, perineorrhaphy and OASIS repair, pelvic-floor reconstruction, Fournier's debridement, vaginal and vulvar reconstruction and perineal-hernia repair, and it is the dissection route for most posterior-approach pelvic procedures.

See also The Vulva, Male Urethra, Female Urethra, The Vagina, and Pelvic Neuroanatomy.

Male perineum muscles

OpenStax Anatomy & Physiology — Muscles of the male perineum. (CC BY 4.0)

Female perineum muscles

OpenStax Anatomy & Physiology — Muscles of the female perineum. (CC BY 4.0)

Boundaries and the Diamond​

The perineum is bounded by four bony and ligamentous landmarks, and a transverse line between the ischial tuberosities divides it into two triangles:

TriangleAnterior boundaryPosterior boundaryLateral boundaryContents
Urogenital (UG)Pubic symphysis + inferior pubic ramiInterischial lineIschiopubic ramiUrethra, perineal membrane; vagina in women; root of penis / clitoris; Bartholin / Cowper's glands
AnalInterischial lineCoccyx + sacrotuberous ligamentsIschial tuberositiesAnal canal, external anal sphincter, ischiorectal fossae, pudendal canal

The ischial tuberosities, pubic symphysis, and coccyx together form the four corners of the diamond. In lithotomy, the UG triangle is anterior and the anal triangle is posterior.

Layered Architecture — Skin to Pelvic Floor​

The UG triangle has five named layers:

LayerContents / noteOperative relevance
SkinHair-bearing; rugated over scrotum / labia majoraPlane of closure in perineorrhaphy and primary-intention perineal repair
Subcutaneous fatAbsent from the scrotal wall, where dartos substitutes; the labia majora contain subcutaneous fat[32]Site of Fournier's fascial spread
Colles' (superficial perineal) fasciaMembranous layer; continuous anteriorly with dartos of scrotum / labia majora and with Scarpa's fascia of the abdominal wall. Fused laterally to the ischiopubic rami and posteriorly to the perineal membraneThe inferior fascial boundary of the superficial perineal pouch; a plane of Fournier's gangrene spread[32]
Superficial perineal pouchSee contents belowThe plane of bulbar urethroplasty, AUS placement, penile / clitoral root surgery
Perineal membraneTwo-region structure: a dorsal portion of bilateral transverse fibrous sheets attaching the lateral vaginal wall / perineal body to the ischiopubic ramus, and a ventral portion of solid tissue intimately associated with the compressor urethrae and urethrovaginal sphincter[2][3][5]The roof of the superficial pouch and floor of the deep pouch; structural anchor of the female striated urogenital sphincter complex and of the male rhabdosphincter; landmark for AUS transcorporal placement
Deep perineal pouchRhabdosphincter (M) / striated urogenital sphincter complex (F) / Cowper's glands (M). Muro and colleagues described a smooth-muscle plate continuous with the rectal wall and, in females, the vaginal wall.[4] Kampelmann and colleagues found that sampled deep-pouch tissue was approximately 80% connective tissue and found no discrete transverse striated muscle sheet.[5] An earlier anatomical review described a deep transverse perineal muscle, reflecting a different interpretation of the region.[9]The plane of pelvic-fracture urethroplasty and membranous urethral dissection; transcorporal AUS cuff placement instead exposes the bulbar urethra and adjacent corpora cavernosa[38]
Pelvic floor (levator ani + fascia)Above the deep pouchThe interface with intrapelvic surgery

Superficial perineal pouch — contents​

MenWomen
Root of the penis — bulb of corpus spongiosum (midline) + paired crura of corpora cavernosa attached to ischiopubic ramiVestibular bulbs (paired) flanking the vagina + paired clitoral crura attached to ischiopubic rami
Bulbospongiosus over the bulbBulbospongiosus / bulbocavernosus flanking introitus
Ischiocavernosus over the cruraIschiocavernosus over the clitoral crura
Superficial transverse perineiSuperficial transverse perinei
—Bartholin (greater vestibular) glands
Perineal branches of the pudendal nerve and internal pudendal arterySame

Layer-by-layer cadaveric dissection of the male perineum from the superficial perineal muscles to the deep perineal space

Cadaveric dissection of the male perineum. (A) Removal of skin, fat and connective tissue exposes the perineal muscles. (B) The superficial transverse perineal muscle (STP), a slender band running from the midline to the ischiopubic ramus (IPR). (C) Deeper dissection shows the perineal membrane (PM), a firm, dense connective-tissue layer. (D) Removal of the perineal membrane exposes a triangular, plate-like smooth-muscle structure (SM) with transverse fibers, continuous with the anterior rectal wall (dashed arrows). BP, bulb of penis; Bs, bulbospongiosus; EAS, external anal sphincter; EUS, external urethral sphincter; Ic, ischiocavernosus; LA, levator ani; LM, longitudinal muscle of rectum; Ur, urethra. From Muro S, et al. Sci Rep. 2025;15(1):23730, Fig. 1 (CC BY).[4]

Deep perineal pouch — contents​

MenWomen
Membranous urethra + rhabdosphincter (external urethral sphincter) — anterolateral omega-shaped loopUrethra with the striated urogenital sphincter complex — rhabdosphincter + compressor urethrae + urethrovaginal sphincter; U-shaped anteriorly
Deep transverse perineal region (traditionally called a muscle); no discrete striated belly in sampled older men[5][9]Deep transverse perineal region (traditionally called a muscle); no discrete striated belly and <1% striated fibers in sampled older women[5][9]
Bulbourethral (Cowper's) glands— (homologues are Bartholin's in the superficial pouch)

Lateral-view diagram of the male levator ani, rhabdosphincter, Cowper&#39;s gland and deep transverse perineal muscle

Male pelvis, lateral view through the bony pelvis. The rhabdosphincter (RS), including its prostatocapsular part, is connected to the inferomedial margin of the levator ani by a thick fascia containing veins, nerves, elastic fibers and smooth muscle (between arrows); levator ani fibers run to the external anal sphincter and anus. Stars mark the layer of the male perineal membrane (not drawn). Below the rhabdosphincter, the deep transverse perineal muscle connects Cowper's gland to the internal surface of the ischial bone. From Hinata N, et al. Biomed Res Int. 2014;2014:906921, Figure 10 (CC BY 3.0).

Lateral-view diagram of the female levator ani, rhabdosphincter, compressor urethrae, urethrovaginal sphincter and perineal membrane

Female pelvis, lateral view through the bony pelvis. The rhabdosphincter (RS) is continuous with the urethrovaginal sphincter (UVS) anteriorly and the compressor urethrae (CU) posterolaterally; these striated muscles sit in an elastic-fiber mesh that anchors the perineal membrane (PM) to the ischiopubic ramus. The perineal membrane extends anteromedially to the space between the vestibular bulb and the vaginal wall, and the levator ani attaches to its superior surface (arrows). From Hinata N, et al. Biomed Res Int. 2014;2014:906921, Figure 11 (CC BY 3.0).

Oblique inferior schematic of male and female pelvic structures showing the superficial transverse perineal muscle, perineal membrane and deep perineal smooth muscle

Pelvic region seen from an oblique inferior angle: (A) male and (B) female pelvic structures. (C) Enlarged male perineum, layered from superficial to deep: the superficial transverse perineal muscle (STP), the perineal membrane (PM), then a triangular, plate-like smooth-muscle structure (SM) in the deep perineal space continuous with the rectal wall. (D) Enlarged female perineum with the same sequence, the smooth-muscle structure being continuous with both the rectal and vaginal walls. Bl, bladder; Bs, bulbospongiosus; EAS, external anal sphincter; Ic, ischiocavernosus; LM, longitudinal muscle of rectum; R, rectum; Ur, urethra; Va, vagina. From Muro S, et al. Sci Rep. 2025;15(1):23730, Fig. 7 (CC BY).[4]

Coronal section through the pelvis and perineum showing the pelvic floor and perineal muscles

Coronal section through the pelvis and perineum. The levator ani forms the muscular pelvic floor; below it the ischiocavernosus and bulbocavernosus muscles and the urogenital diaphragm invest the urethra and erectile bodies, flanked by the fat-filled ischiorectal (ischioanal) fossae. (Public domain, Gray's Anatomy)

The Perineal Body — The Structural Anchor​

The perineal body is a pyramidal fibromuscular structure in the midline between the UG and anal triangles, anterior to the anus.[12] Textbook dimensions are about 20–40 mm craniocaudally in women, and a scoping review found substantial heterogeneity in how ultrasound studies measure it. It receives the insertions of:

  • Bulbospongiosus / bulbocavernosus
  • Superficial transverse perinei
  • Deep transverse perinei
  • External anal sphincter (subcutaneous and superficial parts)
  • Puboperinealis fibers of levator ani (entering the perineal body's mid-region in women)[37]
  • Posterior vaginal wall fibromuscularis (in women)
  • Perineal membrane

A dissection of 56 cadaveric specimens (46 adults, 10 neonates) described the perineal body as a three-layer criss-crossing scaffold and not a simple insertion point:[13]

  1. Superficial layer. External-anal-sphincter fleshy fibers continuous across the midline with bulbospongiosus or bulbocavernosus.
  2. Middle layer. Tendinous extension of the superficial transverse perinei in a criss-cross pattern.
  3. Deep layer. Tendinous fibers of the deep transverse perinei decussating with the contralateral muscle.

Some muscle fibers cross the midline in a figure-8 pattern instead of terminating at the perineal body. Diffusion-tensor imaging in 10 nulliparous women and four men, with a male cadaveric micro-CT for validation, showed continuity between superficial perineal and external-anal-sphincter fibers. In a 43-cadaver dissection series, bulbospongiosus and the superficial EAS were anatomically continuous, with common innervation, in 92.3% of assessable specimens.[6][7] These findings support a connected anatomic model.

The Perineal Complex Triad and urogenital hiatus closure. DeLancey and colleagues propose that the levator ani, perineal membrane and perineal body form a perineal complex triad that closes the urogenital hiatus. MRI of 30 nulliparous women and dissection of 10 cadavers indicated a cranioventral levator line of action, and in cadavers loss of the connection between the left and right perineal membranes through the perineal body widened the hiatus. This is an anatomic hypothesis.[3][10]

Why the perineal body matters in reconstruction. The perineal body connects the posterior vaginal wall, perineal membrane and superficial anal-sphincter region. It is generally wider in women (about 20–40 mm) than in men (about 10–15 mm). Obstetric tears and prior surgery may leave a deficient perineum associated with a wide genital hiatus or posterior-compartment symptoms. Perineorrhaphy repairs selected distal support defects. Apical prolapse and sphincter injury are evaluated and treated separately.

The Anal Triangle​

StructureDimensions / featuresFunction
Internal anal sphincter (IAS)~0.3–0.5 cm thick; thickened circular smooth muscle of the rectum[15]Under autonomic control; major contributor to resting anal tone.[14][16] Injury can contribute to passive leakage, but symptoms are multifactorial.[22]
External anal sphincter (EAS)~0.6–1.0 cm thick; commonly described in subcutaneous / superficial / deep portions[15]; predominantly slow-twitch, fatigue-resistant fibersSomatic sacral innervation through variable pudendal and direct branches; voluntary squeeze reinforces closure.[6][14] Injury can contribute to urgency-associated leakage.[22]
PuborectalisLevator-ani sling drawing anorectum anteriorlyContributes to the anorectal angle, which changes during squeeze and defecation; measured angles vary with technique and individual anatomy.[15]
Ischiorectal (ischioanal) fossaFat-filled paired spaces lateral to the anal canal; bounded by obturator internus laterally, levator ani superomedially, and the anal canal mediallyCommunicates posteriorly via a deep postanal space — the anatomic path of horseshoe abscesses
Pudendal (Alcock's) canalFascial tunnel on the medial surface of obturator internusCarries the pudendal nerve and internal pudendal vessels
Anococcygeal body (ligament)Fibromuscular raphe between anal canal and coccyxReceives fibers of levator ani and EAS

The entire sphincter complex extends approximately 4 cm up the anal canal, with the EAS overlapping the distal IAS by approximately 1–2 cm.

EAS innervation varies by subdivision​

In the 43-cadaver series of Plochocki and colleagues, the inferior rectal nerve arose from S3 and S4 separately from the pudendal nerve in 33 of 37 evaluable specimens (89.2%) and innervated only the subcutaneous EAS in 34 of 36 evaluable specimens (94.4%).[6] The superficial EAS received perineal-nerve branches and the deep EAS a branch from the nerve to levator ani.[6] The authors interpret this as potential functional independence of the three EAS portions.

Vascular Supply​

Arterial​

The dominant supply is the internal pudendal artery (anterior division of the internal iliac). It exits the pelvis through the greater sciatic foramen, wraps around the ischial spine, re-enters the perineum through the lesser sciatic foramen, and runs through Alcock's canal on the medial obturator internus. It gives the following branches:

BranchTerritory
Inferior rectal arteryAnal canal, EAS, perianal skin
Perineal artery (→ posterior scrotal / labial, transverse perineal)Superficial pouch, scrotum / labia, perineal body
Artery of the bulb of the penis (M) / vestibular bulb (F)Bulb of spongiosum / vestibular bulb
Urethral artery and dorsal / deep artery of the penis (M) / clitoris (F)Urethral corpus spongiosum; dorsal NVB; cavernosal / corporeal engorgement

The external pudendal arteries (from the femoral) supply anterior scrotum, anterior labia majora and mons skin. The Martius labial fat-pad flap can be based superiorly on external-pudendal branches or inferiorly on internal-pudendal branches, and pedicle choice sets its reach.

Venous and lymphatic​

Venous drainage parallels the arteries. The deep dorsal vein of the penis drains into the prostatic (Santorini's) plexus; the deep dorsal vein of the clitoris drains into the vesical venous plexus, with communicating female pelvic plexuses.[23] Superficial veins drain toward the external pudendal or saphenous system.

Lymphatic drainage is split:

  • Perineal skin and superficial structures drain to the superficial inguinal nodes
  • Urethral drainage depends on segment: the male anterior urethra drains first to superficial and deep inguinal nodes and then to pelvic nodes, whereas the male posterior urethra drains to pelvic nodes. The female distal two-thirds drain first to inguinal nodes and the proximal third to pelvic nodes.[28]
  • This split drives the inguinal-LND template in vulvar / penile SCC and the pelvic-LND template in posterior urethral cancer.

Innervation — The Pudendal Nerve Dominates​

Pudendal nerve (S2–S4)​

The pudendal nerve is a major perineal nerve. After traversing Alcock's canal, it gives perineal and dorsal genital branches; the inferior rectal nerve may instead arise directly from S3/S4, as in the cited cadaveric series.[6] The branches and related nerve are listed below:

BranchTerritory / function
Inferior rectal nerveEAS motor; perianal sensation
Perineal nerve — deepBulbospongiosus, ischiocavernosus, transverse perinei, external urethral rhabdosphincter (via Onuf's nucleus)
Perineal nerve — superficial (posterior scrotal / labial)Posterior scrotum / labia majora sensation
Dorsal nerve of the penis / clitorisDominant sensory input to the glans

Additional peripheral contributions:

  • Ilioinguinal and genital branch of genitofemoral (L1–L2). Anterior scrotum, labia majora and mons
  • Posterior femoral cutaneous, perineal branch. Lateral perineum and upper medial thigh
  • Autonomic fibers from the inferior hypogastric plexus. Erectile tissue, glands, and pelvic viscera; cavernous and clitoral nerves ride with the lateral NVB and with the posterior route (see The Penis)

Onuf's nucleus​

A sacral (S2–S4) somatic motor-neuron pool that innervates the striated external urethral and external anal sphincters. Relative preservation in amyotrophic lateral sclerosis has been reported. Sphincter function in advanced disease still needs its own assessment.

Dorsal penile / clitoral nerve — the sensory-critical branch​

Runs along the dorsal erectile structures after passing beneath the pubic arch (see The Penis / The Vulva). Branching and crossing vary, so no clock-face position is a reliably nerve-free dissection or injection plane. Injury during genital or perineal reconstruction can cause sensory loss.

Physiology​

The perineum supports four overlapping functions, and preserving or reconstructing one can trade off against another.

Continence​

  • External urethral sphincter (voluntary, pudendal) provides phasic closure on cough and Valsalva and a tonic contribution to resting urethral pressure. The guarding reflex recruits the sphincter reflexively before abdominal pressure rises.
  • Anal continence depends on a layered mechanism:[14][15][16][18][21]
    • Mechanical. IAS tone (bulk of resting pressure), EAS squeeze (voluntary reinforcement), puborectalis-generated anorectal angle (flap-valve), and the sealing effect of anal mucosal folds and vascular cushions.
    • Sensory. Pelvic-floor stretch receptors detect rectal distension; anal-transition-zone receptors discriminate gas, liquid, and solid ("rectoanal sampling").
    • Reflex. The rectoanal inhibitory reflex relaxes the IAS on rectal distension, allowing sampling. Involuntary EAS, puborectalis and sphincter-of-O'Beirne contractions, together with retrograde propagating sigmoid and rectal motor patterns, prevent continuous anal outflow between defecations.[18]
  • Pelvic-floor and perineal support. The perineal body, perineal membrane, levator-ani complex, urethral support and sphincter function interact during rises in abdominal pressure. Support defects may contribute to female stress urinary incontinence, and no single perineal structure explains most cases (see The Vagina).

Sexual function​

  • Ischiocavernosus. Contracts during sexual response and compresses the crura, contributing to penile rigidity; this was studied in mammalian penile tissue.[8]
  • Bulbospongiosus (bulbocavernosus). In men, contracts to expel semen and urine through the urethra and maintains intraspongiosal pressure; in women, contributes to introital narrowing, clitoral engorgement via vestibular-bulb compression, and the rhythmic contractions of orgasm.
  • Erectile tissue of the clitoris, vestibular bulbs, corpora cavernosa, and corpus spongiosum. Autonomic-driven engorgement during arousal.
  • Glans sensation. Carried prominently by dorsal penile or clitoral nerve branches, with variable branching and overlapping sensory supply.
  • Three-part reflex control. Erection is parasympathetic-dominant (S2–S4, NO-mediated vasodilation); emission is sympathetic-dominant (T10–L2, contraction of vas deferens, seminal vesicles, and prostate).[19][20] Ejaculatory expulsion uses somatic S2–S4 and pudendal pathways and rhythmic perineal-muscle contractions.[19][20][27] A postmortem study of galaninergic neurons (6 men, 6 women) and 384 men with clinically complete spinal cord injury support a spinal ejaculation generator at L3–L5. Injury involving L3–L5 was the sole independent predictor of failed ejaculation with penile vibratory stimulation.[24]

Defecation​

  • Voluntary relaxation of puborectalis opens the anorectal angle.
  • Voluntary relaxation of EAS combined with reflex IAS relaxation on rectal distension permits evacuation.
  • Perineal-body support contributes to posterior vaginal-wall support. A distal support deficit can coexist with rectocele or obstructed defecation, and symptoms also depend on other pelvic structures and bowel function.

Childbirth​

  • The perineum stretches markedly during the second stage of labor.
  • The perineal body is the most common site of obstetric laceration.[1]
  • Episiotomy. ACOG recommends restrictive over routine episiotomy (Level A).[1] When episiotomy is needed, a mediolateral cut may be preferred because a midline cut is associated with a higher risk of anal sphincter injury, although limited data link mediolateral episiotomy with more perineal pain and dyspareunia (ACOG Level B).[1] In nulliparous operative vaginal births, the 2026 IUGA guideline reports that mediolateral or lateral episiotomy is associated with lower OASIS risk, especially with forceps (Grade A), and recommends a 60° angle from the midline at crowning (Grade C).[36]
  • Obstetric anal sphincter injuries (OASIS). 3rd-degree tears involve the EAS, with or without IAS injury (3c includes both); 4th-degree tears involve EAS, IAS and anorectal mucosa. Offer a rectal examination after every vaginal birth to detect OASIS or an isolated rectal buttonhole tear (IUGA Good Practice Point).[36] Primary repair includes separate IAS repair when identifiable; partial-thickness EAS injury is approximated end-to-end, while full-thickness EAS injury can be repaired end-to-end or by overlap. Give intravenous broad-spectrum antibiotics during repair .[36] Later fecal-incontinence treatment follows evaluation and is not set by tear grade alone.[22][25][36]
  • Levator ani avulsion is an often unrecognized component of birth injury. In an MRI study, 32 of 160 vaginally primiparous women (20%) had a visible levator defect and none of 80 nulliparous women did.[11] Half of the primiparous women had stress incontinence; the sample was not population-based.[11] Levator avulsion is associated with later prolapse.

Vascular Anatomy of Perineal Perforator Flaps​

Beyond the internal and external pudendal supply described above, a microdissection of 11 adult cadavers (22 sides) mapped four relatively constant perforating arteries relevant to perforator-flap planning. Vascular anatomy is confirmed before a flap is planned.[17]

  1. Inguinal perforating branch of the superficial external pudendal artery
  2. Perineal perforating branch of the superficial external pudendal artery
  3. Perforating branch of the anterior cutaneous branch of the obturator artery
  4. Perforating branch of the lateral branch of the posterior scrotal / labial artery

These form upper, middle, and lower anastomoses in the deep fascia above the adductor compartment, the anatomic substrate for the pudendal-thigh (Singapore), internal pudendal artery perforator (IPAP), and anterior obturator artery perforator flaps used in vaginal, vulvar, and perineal reconstruction.

Sex Differences for the Reconstructive Surgeon​

FeatureMenWomen
UG-triangle contentsSingle pass-through (urethra); bulb + crura of penisDouble pass-through (urethra + vagina); vestibular bulbs + clitoral crura
Perineal bodyNarrower (~10–15 mm); less structural roleWider (~20–40 mm); central reconstructive target for posterior compartment and EAS support
Sphincter geometry in deep pouchRhabdosphincter as anterolateral omega-loop around membranous urethraSemicircular rhabdosphincter with distinct compressor urethrae and urethrovaginal sphincter components associated with the perineal membrane[9]
Homologue glandsCowper's (bulbourethral) — in the deep pouchBartholin (greater vestibular) — in the superficial pouch
Scrotum / labia majoraScrotum + dartosLabia majora + dartos; Martius flap territory
Erectile-organ homologyPenis has glans, shaft, paired crura and a dorsal sensory nerveClitoris has glans, body, paired crura and a dorsal sensory nerve; urethra remains anatomically separate
Operative targetsBulbar urethroplasty, AUS, radical perineal prostatectomy, PFUI repairPerineorrhaphy, OASIS repair, vestibulectomy, Martius flap harvest, vaginal reconstruction

Clinical Correlations for the Reconstructive Surgeon​

  • Bulbar urethroplasty. The bulbar urethra sits in the superficial perineal pouch invested by bulbospongiosus. A perineal incision and midline split of bulbospongiosus permit mobilization of the corpus spongiosum for anastomotic or augmentation repair. Barbagli and colleagues also described a muscle- and nerve-sparing approach that leaves the central perineal tendon intact; their 12-patient feasibility series did not establish that it prevents ejaculatory dysfunction or perineal weakness.[29]
  • Artificial urinary sphincter (AUS) cuff placement. Perineal approach to the bulbar urethra; cuff placed around the corpus spongiosum distal to the crura. Transcorporal cuff placement (through the tunica of the corpora cavernosa) reinforces a compromised spongiosum in reoperative or radiation cases.
  • Radical perineal prostatectomy and perineal approach to the prostate. Curved incision anterior to the anus, through the central tendon, between ischiocavernosus muscles, exposing the prostate posterior to the bulb. Useful historically and in selected patients where abdominal access is contraindicated.
  • Pelvic-fracture urethral injury (PFUI) repair. The perineal anastomotic approach mobilizes the bulbar urethra and opens the deep perineal plane to expose healthy proximal urethra. Crural separation is routinely performed; inferior pubectomy and supracrural rerouting are added selectively if needed for a tension-free anastomosis. A transpubic abdominoperineal extension may be required in unusual complex or redo cases when proximal access remains inadequate.[33]
  • Perineorrhaphy and OASIS repair. Reconstruct disrupted perineal-body muscles according to the defect. For a fourth-degree tear, close torn anorectal mucosa first. Identify and repair the IAS separately when torn; use end-to-end EAS approximation for partial-thickness tears and either end-to-end or overlap for full-thickness tears, then repair perineal muscles and overlying tissue. After repair, perform a rectal examination and remove any suture entering the anorectal mucosa.[25]
  • Vestibulectomy for vulvodynia. Excision of painful vestibule with vaginal advancement flap, the neuroproliferative vestibulodynia operation. See The Vulva.
  • Martius labial fat-pad flap. Interposition flap for VVF, RVF, UVF, urethral diverticulectomy, complex perineal wounds. Harvested through a vertical labia-majora incision; pedicle choice (superior external pudendal versus inferior internal pudendal) dictates reach. See The Vulva.
  • Gracilis muscle flap. Reliable regional flap for large perineal defects (rectovaginal / rectourethral fistulae, perineal hernia after APR, vulvar reconstruction). The main pedicle varies: in a dissection of 84 gracilis muscles, it arose from an adductor artery in 73%, the medial circumflex femoral artery in 19.2%, and both in 7.7%.[34]
  • Pudendal-thigh (Singapore) fasciocutaneous flap. Axial groin-crease flap used for vaginal, vulvar, and perineal reconstruction. In five cadavers, posterior labial/scrotal branches of the internal pudendal artery, obturator branches, and external pudendal branches formed three vascular territories; the authors suggested a more medial design to address apical necrosis risk in large flaps.[35]
  • Fournier's gangrene. Necrotizing fasciitis of the dartos / Colles' / Scarpa's plane; testes and cord usually spared. Emergency wide debridement, broad-spectrum antibiotics, diversion as needed, delayed reconstruction.
  • Perineal hernia. Post-APR / post-exenteration defect through the levator and perineal floor; repair may use mesh, regional flap tissue (for example gracilis or VRAM), or a combination selected for the defect and tissue quality.
  • Ischiorectal fossa abscess / horseshoe abscess. Drained through the anal triangle; attention to the deep postanal space where horseshoe abscesses bridge. Unrecognised horseshoe extensions produce recurrent abscess / complex fistula.
  • Pudendal neuralgia and Alcock's canal entrapment. Perineal or genital pain may worsen while sitting. The Nantes criteria support a clinical diagnosis. AUA 2025 notes that the criteria lack clinical validation and do not cover every possible entrapment site. Its ungraded discussion advises against open release because of scarring and re-entrapment risk, while describing limited laparoscopic and robotic evidence.[26] Guideline differences are discussed under Pudendal neuralgia.
  • Sacrospinous ligament fixation (SSLF). Vaginal-vault suspension to the sacrospinous ligament near the ischial spine risks nearby nerves and vessels. In a cadaveric suture-placement study, nerves to coccygeus and levator ani lay closest to the sutures, while the pudendal nerve remained a lateral hazard.[30] Postoperative nerve entrapment can present with gluteal or perineal pain, including suspected pudendal neuropathy.[31]
  • Radical vulvectomy and perineal reconstruction. After wide local excision or radical vulvectomy ± inguinal LND. Reconstruction ladder: primary closure, then local V-Y or rhomboid flaps, then Singapore (pudendal-thigh) flap, then gracilis or VRAM myocutaneous flap for large defects.
  • Cauda equina and S2–S4 lesions. May cause saddle sensory change and bladder, bowel or sexual dysfunction, with patterns varying by lesion. New saddle sensory symptoms, retention or progressive deficits warrant urgent evaluation, and incomplete saddle anesthesia does not exclude cauda equina syndrome.
  • Male sling procedures. Selected transobturator slings for post-prostatectomy SUI support or reposition the bulbar urethra, with mechanisms and fixation that vary by device.
  • Pelvic radiation sequelae. Radiation can impair tissue healing and complicate fistula repair. Well-vascularized interposition tissue (Martius, gracilis or omentum) is often used in complex irradiated repairs.
  • Gender-affirming surgery (perineal component). Phalloplasty and metoidioplasty use perineal tissue for urethral lengthening; vaginoplasty creates the neovaginal cavity in the plane between urethra and prostate (anterior) and rectum (posterior), with the perineal body preserved to support the introitus.

References​

1. Committee on Practice Bulletins—Obstetrics. "ACOG Practice Bulletin No. 198: Prevention and Management of Obstetric Lacerations at Vaginal Delivery." Obstet Gynecol. 2018;132(3):e87–e102. doi:10.1097/AOG.0000000000002841. Interim update; reaffirmed 2025.

2. Stein TA, DeLancey JO. "Structure of the Perineal Membrane in Females: Gross and Microscopic Anatomy." Obstet Gynecol. 2008;111(3):686–693. doi:10.1097/AOG.0b013e318163a9a5

3. DeLancey JO, Pipitone F, Masteling M, et al. "Functional Anatomy of Urogenital Hiatus Closure: The Perineal Complex Triad Hypothesis." Int Urogynecol J. 2024;35(2):441–449. doi:10.1007/s00192-023-05708-w

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