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Retroperitoneal anatomy

Renal fascia

• Perirenal space: contains kidney, ureter, and adrenal
• Pararenal space: space outside of Gerota's fascia
• Gerota fascia: surrounds perirenal space, open inferiorly which can lead to inferior drainage of perinephric fluid collections

Renal vessels

• Left renal vein longer than right side, crosses over aorta
• Lumbar vein may drain into left renal vein and can be avulsed during surgery
• Renal artery branching: renal artery, segmental artery (posterior, apical, upper, middle, lower), lobar artery, interlobar artery, arcuate artery, interlobuar artery, afferent artierioles
• Segmental arteries: lack anastomoses and injury can lead to focal renal infarction
• Accessory renal arteries: seen in 25-28% patients
• 5% patients have the main/accessory right renal artery pass anterior to IVC
• Adrenal vascular supply: arterial comes from inferior phrenic, adrenal, and renal arteries, venous drainage via adrenal veins

Collecting system anatomy

• 5-14 minor calyces, grouped as upper, middle, and lower
• Compound calyces: always for upper, rare for middle, common for lower
• Anteroposterior orientation: most superior calyces posterior, most inferior calyx anterior, next most inferior calyx posterior
• Brodel kidney: posterior calyx 20 degrees posterior and anterior calyx 70 degrees anterior to frontal plane, seen in most right kidneys
• Hodson kidney: posterior calyx 70 degrees posterior and anterior calyx 20 degrees anterior to frontal plane, seen in most left kidneys

Ureter

• Main points of obstruction: UPJ, crossing the iliac vessels, UVJ
• Superior ureter receives blood medially (aorta), inferior ureter receives blood laterally (iliac vessels)
• Ureter identified intraoperatively when crossing common iliac bifurcation
• Ureter passes posterior to uterine artery, vulnerable to injury during division of uterine pedicle during hysterectomy

Somatic nerves

• Ilioinguinal: innervates skin over upper medial thigh and anterior scrotum, runs alongside spermatic cord within inguinal canal
• Genitofemoral: genital branch innervates cremaster muscle and anterior scrotum, femoral branch innervates upper anterior thigh, runs over psoas muscle and can be injured during psoas hitch
• Obturator: runs inferior to obturator canal, provides hip adduction, can be stimulated during lateral wall bladder tumor resection
• Femoral: innervates knee extension and hip flexion muscles and anterior thigh skin, compression injury during retractor placement against inguinal ligament, stretch injury from prolonged hip flexion during low lithotomy

Pelvic anatomy

Umbilical ligaments (on anterior abdominal wall)

• Median: urachus, divided during prostate/bladder surgery
• Medial: obliterated umbilical artery
• Lateral: inferior epigastric, avoid lacerating during trocar placement

Prostate

• Cavernosal nerves travel within the parietal pelvic fascia AKA lateral prostatic fascia, can be preserved/damaged during prostatectomy
• Inferior vesical artery supplies prostate, drainage via periprostatic plexus which drains into the internal iliac veins
• Neurovascular bundles: located within prostatic fascia at posterolateral position

Divisions of the Male Urethra

• Bladder neck: surrounded by continued bladder muscles
• Prostatic urethra: surrounded by prostate, contains verumontanum and prostatic utricle (Mullerian remnant)
• Membranous urethra: traverses perineal membrane, surrounded by external sphincter, unattached to any fixed structures
• Bulbar urethra: closer to dorsal side of corpus spongiosum, turns upwards into perineal membrane, transitions from urothelium to squamous epithelium
• Penile urethra: centered within corpus spongiosum
• Fossa navicularis: widened urethra within glans
• Meatus: ventral slit, urethral termination
• Glands of Littre: mucus-secreting cells that lubricate urethra prior to ejaculation

Penile vasculature and drainage

• Internal pudendal artery branches into the corporal, dorsal, and bulbourethral arteries
• Bulbourethral arteries: supply corpus spongiosum, urethra, and glans, transected during urethroplasty
• Corporal arteries: supply corpora cavernosa, helicine arteries dilate with erections
• Dorsal arteries: between dorsal vein (medial) and nerve (lateral), supply spongiosum and urethra
• Penile skin: supplied by external pudendal branches from the femoral artery
• Venous drainage: superficial dorsal vein drains to saphenous vein, cavernosal sinuses drain to emissary veins draining to prostatic plexus and internal pudendal veins
• Lymphatics drain into inguinal nodes

Testicular/scrotal vasculature and drainage

• Arterial supply: testicular (aorta), vas deferens (internal iliac), and cremasteric (inferior epigastric) arteries
• Prior staged orchiopexy: testicular blood supply may be mainly from vas deferens artery, take care if performing vasectomy
• Pampiniform plexus: vein network surrounding testis and artery, allows for countercurrent heat exchange, form 2-3 veins at level of inguinal canal
• Venous drainage: left gonadal vein drains into left renal vein, right gonadal vein feeds directly into IVC (can be avulsed with improper retraction)
• Lymphatic drainage: drain right to left in retroperitoneum, left testis drains to left paraaortic and interaortocaval nodes, right testis drains to interaortocaval nodes and right paracaval nodes
• Testicle does not have somatic innervation, only tunica vaginalis and scrotum
• Scrotal vasculature and nerve supply do not cross median raphe

Female pelvic support levels

• Level 1: cardinal and uterosacral ligaments + parametrium + paracolpium support vagina and uterus, weakness leads to apical prolapse
• Level 2: paravaginal attachments to levator ani and ATFP, supports anterior vaginal wall, weakness leads to anterior wall prolapse
• Level 3: distal vaginal attachments to urethra and levator ani, supports urethra, weakness leads to urethral hypermobility, distal rectocele, and perineal descent

Inguinal anatomy

Inguinal node dissection

• Femoral triangle: inguinal ligament superiorly, sartorius muscle laterally, adductor longus muscle medially, flore created by pectineus medially andiliopsoas laterally
• Saphenofemoral junction is ~2 fingers lateral and inferior to pubic tubercle
• Fascia lata separates superficial and deep lymph node groups
• Superficial ILNs: central (around saphenofemoral junction), superolateral (around superficial circumflex vein), inferolateral (around lateral femoral cutaneous and superficial circumflex veins), superomedial (around superficial external pudendal and superficial epigastric veins), and inferomedial (around greater saphenous vein)
• Node of Cloquet: most cephalad of deep ILNs

Embryology

Nephric system

• Pronephros functional excretory unit until 4wks, then degenerates
• Mesonephros: functional excretory unit 4-8wks, degenerates except gonadal ridge
• Metanephros: forms the kidney, functions after 8wks

Development factors

• SRY: gene on Y chromosome, induces gonadal ridge to become testis (week 7), absence leads to ovary
• Mullerian inhibiting factor (MIF): produced by sertoli cells, causes degeneration of Mullerian ducts (week 8-10), absence leads to Mullerian presence
• Testosterone: produced by leydig cells, causes maturation of Wolffian ducts (week 8-10), absence leads to Wolffian degeneration
• Dihydrotestosterone (DHT): converted by 5a-reductase, causes development of male external genitalia, absence presents genital maturation

Developmental homologues

Embryologic structure	Male structure	Female structure
Mesonephros (genital ridge)	Testis	Ovary
Mesonephric (Wolffian) duct	Bladder trigone
	Ejaculatory ducts	Gartner duct
	Seminal vesicles	(no female homologue)
Ureteric bud	Ureter, renal pelvis, collecting ducts
Metanephros	Kidney
Paramesonephros	(degenerates)	Fallopian tube, uterus, cervix, upper vagina
Urogenital sinus	Prostatic urethra	Urethra
	Cowper glands	Bartholin glands
	Prostate	Skene glands
	(no male homologue)	Lower vagina
	Bladder, urachus
Genital tubercle	Penis	Clitoris
Genital swellings	Scrotum	Labia majora
Urethral folds	Penile urethra	Labia minora
Urogenital groove	Penile urethral lumen	Vestibule
Genital ligament	Gubernaculum	Round ligament

Vestigial structures

Duct	Male remnant	Female remnant
Wolffian	Appendix epididymis Paradidymis (Organ of Giraldes)	Appendix vesiculosa Epoophoron (parovarium, organ of Rosenmuller) Paroophoron of Waldeyer Gartner duct
Mullerian	Appendix testis Prostatic utricle	Morgagni hydatid