• Embryology

• Germ Layers: Mesoderm (nephric system, gonads, wolffian ducts, mullerian ducts), Endoderm (Cloaca and membrane), Ectoderm (External genetalia)

• Gonads start as genital ridges –>male to female differentiation at 6 weeks
• Both mesonephric and paramesopnephric duct (male and female ducts) are present in developing fetus)
• Regression of paramesonephric ducts –> influenced by mullerian inhibiting substance which is produced by sertoli cells –> would typically develop into fallopian tubes, uterus, and upper portion of vagina in absence of mullerian inhibiting substance
• Development of mesonephric ducts –> produced by interstitial cells of leydig –> influenced by testosterone analog –> development of epididymis, vas deferences, and seminal vesicles
• Female differentiation is known as the “default” with the absence of mullerian inhibiting substance –> vaginal plate apoptosis by 22 weeks develops vaginal canal, process complete by fifth gestational month

• Anatomy
Regions:

• Perineum: includes the area between the vagina and the anus in women and the area between the scrotum and the anus in men. Also described as the pelvic outlet- which is the are between the pubic symphysis and coccyx. 

• Contains two fascial layers superficial and deep –> deep layer is continuous with colles fascia of the thigh

• Male: Penis: consists of root, body, and epithelium (glans penis)

• Penile Layers: Skin, dartos fascia, Bucks Fascia, and tunica albuginea
• Neurovascular Bundle: deep dorsal vein, dorsal artery and paired dorsal nerves of the penis
• Erectile tissue: paired corpora cavernosa and corpora spongiosum; urethra passes through corpus spongiosum and the meatus, ends at the tip of the glans penis
• Scrotum:  

• Female: Vulva- includes mons pubis labia majoria, minora, clitoris, and vestibule

• Labia majora: skin, camper’s fascia, and colle’s fascia (continues with scarpa’s)

• Labia majora has inferior attachment on the ischiopubic rami that prevents the spred of hematomas and infections

• Labia minora: folds of skin without fat 
• Clitoris: derived from undifferentiated phallus and has paired corpora, vestibular bulbs and glans
• Vagina: muscular tubular structure that extends from the vulva to the uterus –> opening located posterior to the urethra and is closed by the labia minora

• Length (typically) 6cm across anterior wall and 7.5cm across posterior wall; width 2.6-3.25cm

• Arterial supply: 

• Internal pudendal artery (supplies perineum) from the internal iliac

• Perineal artery –> supplies perineum and scrotum/vulva
• Common penile artery: three branches (bulbourethral, dorsal, deep cavernosa)–> travels below Buck’s fascia and above the tunica albuginea (remember tunica albuginea envelops the corpus cavernosum)

• Superficial and deep external pudendal artery

• Branch off of the medial side of femoral artery
• Supplies skin of lower abdomen and anastomoses with the internal pudendal artery to supply the genitalia

• Testicular ovarian arteries: branch off aorta where gonads originate
• Uterine artery: supplies vagina

• Innervation:

•  Pudendal nerve: (s2-4)–> follows course internal pudendal artery; perineal nerve (deep motor branch); dorsal nerve of penis/clitoris; posterior scrotal/labial nerves; inferior anal nerves
• Ilioinguinal nerve (L1): anterior scrotal/labial nerve –> root of penis/mons and upper part of scrotum/labium majora (innervate the anterior vulva)
• Congenital Defects

• Vaginal agenesis:

• Hypospadias: male urethra incomplete and exits ventrally
• Epispadias

• Acquired

• Cancer, Trauma, Peyronie’s disease (correlates with dupuytren’s)
• Reconstruction considerations: high bacterial counts (second highest in body), avoiding wound contamination with stool and urine, pressure necrosis, high infection and dehiscence rates–> 66% dehiscence rate 

• Chemoradiation (inflammation/ulceration), fibrotic changes
• Poor nutritional status
• Goal of reconstruction: to return to sexual activity (50% actual return)

• Classification of Defect: (cordeiro et al)

• Partial Type I 

• Anterior or lateral wall (ia), posterior wall (ib)

• Circumferential II

• Upper 2/3 or total

• Treatment for vaginal defects: 

• Singapore:

• First described as 15x6cm skin flap with medial incision in the thigh crease lateral to the hair bearing area, posterior flap at the posterior fourchette
• Arterial supply is posterior labial arteries (branches of pudendal artery)
• Sensation via posterior labial branches of the pudendal nerve
• Elevated in fasciocutaneous plane of the deep fascia of the thigh, directly over adductor muscles –> transposed 70 degrees. Donor site primarily closed 
• Several variations

• Modified singapore flap
• Pudendal thigh flap or singapore flap based off of superficial perineal artery
• Superficial perineal nerve supplies sensation to flap for IMMEDIATE sensation post operatively
• Good for posterior vaginal reconstruction
• Used for Ia defects (unilateral or bilateral)

• Vertical rectus flap

• Most evidence for APR or LAR defects (large composite defects) s/p radiation
• Ib defects (posterior vaginal wall defects)
• Typically after colorectal cancer extending into the vaginal septum and can include vaginal wall and pelvic contents
• Brings healthy tissue into area without radiation

• Mathis and Nahai III; blood supply superior and deep inferior epigastric (based on deep inferior epigastric)
• Skin paddle designed paramedian, primary abdominal wall closure
• Iia (circumferential upper 2/3) may be reconstructed with rolled VRAM, usually after cervical or other gynecologic malignancies–> flap width usually 12-15cm

• Bilateral gracilis flap

• Good for total vaginal reconstruction with or without skin paddle

• Inconsistent sensation; reliable perforator
• Unilateral or bilateral
• Iib circumferential total defects use bilateral myocutaneous flaps (typically after total pelvic exenterations)
• Arterial supply medial femoral circumflex artery with secondary minor pedicles derived from the superficial femoral artery in a segmental fashion
• Identification: line drawn from pubic tubercle and semitendinous tendon (denotes anterior border of gracilis) –> pedicle will enter 7-10cm  below the pubic tubercle in space between adductor longus and magnus

• Skin island may be as large as 6-20cm along the proximal 2/3 of muscle; make sure to design over adductor to include all of the perforators
• Vulvar reconstruction: typically from SCC or other types of skin cancer; lichen schlerosis, HPV

• Divided into upper third (mons and labia), middle third (labia proper), lower third (vaginal orifice and perineum)
• Upper third defects may be closed primarily, larger defects with pedicled ALT
• Pedicled ALT

• For large upper third vulvar defects, based on descending branch of the lateral circumflex artery (between vastus lateralis and medialis)
• Perforators found at midpoint between ASIS and patella, 5cm inferior and superior
• Dissection occurs with anterior incision first, the flap then transferred in subcutaneous plane
• May tunnel under rectus and sartorius to add pedicle length; muscle may be added if dead space is present

• Middle third defects:

• Singapore flap, gracilis, gluteal fold flaps
• Gracilis most typically used (great for cases with radiation)
• Lotus flap: modification of singapore flap uses superficial perineal artery perforators, design of lotus

• Lower third defects: (vaginal orifice or perianal)

• Gluteal fold flap: marked preoperatively with patient in standing position

• Flap located in triangle formed by ischial tuberosity, anus, and vaginal orifice or scrotum
• Skin flap elevated under fascia of gluteus maximus
• Based on internal pudendal perforators, may include posterior cutaneous nerve of the thigh if sensory component desired
• Treatment for Penile defects/reconstruction: typically after resection of lichen sclerosis, carcinoma of penis, neuroendocrine tumors

• Classified as partial or complete

• Radial forearm flap: gold standard for total penile phalloplasty and gender reaffirming surgery

• Innervated skin island- antebrachial cutaneous–> coapted to the pudendal nerves or dorsal nerve to the penis
• Forearm skin for neourethra from a central urethral strip, is tubed over a 12-14 F silicone urinary catheter

• Free sensate osteocutaneous fibula flap

• Main advantage to fibula flap over RFFF is avoidance of prosthesis to provide erectile and sexual function

• Less conspicuous donor site
• Innervated skin island- via peroneal nerve
• Will need FTSG for neourethra- more likely to have urethral constriction

• Pedicled ALT

• Tube in tube technique with preservation of the lateral femoral cutaneous nerves

• Neophallus constructed while flap in thigh

• Scrotal Reconstruction: – in absence of prior radiation therapy, STSG typically used

• Superomedial thigh flaps with pouch
• Pedicled ALT
• Gracilis

• TIssue expansion

• Examples:

• Traumatic Amputation of Penis: attempt microvascular replantation –> keep on saline soaked gauze, place in sterile bag, place bag in slush –> order urinary diversion with suprapubic catheter, urethral anastomosis over foley, corporal body coaptation by approximating tunica albuginea, microsurgical anastomosis of dorsal vessels, nerves, skin closure
• Blood flow: Internal iliac –> internal pudendal artery –> deep dorsal penile arteries
• Replantation via the Dorsal Penile Artery has best outcomes for sexual urinary sensation 

• Fornier’s Gangrene

• Transgender

• Male to Female: Start hormonal therapy 2 years prior, psychiatric clearance

• Breast augmentation
• Rhinoplasty

• Male pattern hair removal
• Reduction of thyroid cartilage
• Feminizing genital surgeries (penectomy, penile inversion, skin grafts, intestinal substiution)

• Female to Male: start hormonal therapy and introduction as male for 2 years, psychiatric clearance

• Mastectomy (typically is mastectomy with free nipple graft especially with ptosis)

• Hysterectomy/oophorectomy
• Phallus construction
• neoscrotum

• Psychosocial: must have continuous disturbance for at least 2 years