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General Surgery
Pelvis and Perineum Pelvic Sidewall, Pelvic Floor
Built from Skandalakis' Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery
What’s inside
13 sections · 159 slides
Overview
- Scope of this topic
Pelvic sidewall: orientation
- Pelvic wall is the source of most surgical problems, anatomic complications and technical difficulty in lower abdominal surgery General surgeons, urologists and gynaecologists must all know its topographic anatomy Oncologic surgeons depend on it for radical cancer operations Organ-based specialisation has fragmented knowledge of pelvic anatomy Adjacent specialties operate in the same region with restricted knowledge of neighbouring structures
- Pelvic bones arise from the anterior and posterior compartments of the limb bud mesoderm Pubis and ischium are of anterior origin Ilium is of posterior origin Detailed embryology of the other pelvic wall structures is dealt with in the organ chapters
- True (lesser or minor) pelvis lies between the pelvic brim and the pelvic floor Bounded by the linea terminalis above and the pelvic and urogenital diaphragms below Distinction is useful to the urologist, gynaecologist and urogynaecologist For many general surgeons operating low in the abdominopelvic cavity it has little practical value Hard to name organs that reside only in one or the other, so both are described together here
- Contains portions of the urinary, genital and digestive tracts Distal ureters, urinary bladder, female genitalia, prostate, rectosigmoid, proximal rectum, small bowel Promontory of the sacrum and the iliopectineal line form the pelvic brim Pelvic diaphragm with the urogenital diaphragm forms the floor Sacrum, hip bones, piriformis and obturator internus with their fasciae form the wall Greater sciatic foramen transmits piriformis, sciatic nerve and the gluteal and perineal neurovasculature
- Linea terminalis separates the false pelvis above from the true pelvis below Formed by the pubic crests, superior symphysis pubis, pectineal lines, arcuate lines and sacral promontory Below it: rectum, empty bladder, non-pregnant uterus and adnexa, vagina, terminal male reproductive tract Also the sacral plexus and pelvic neurovascular structures Greater omentum, transverse and sigmoid colon and ileum are unpredictable temporary residents
- Intraperitoneal anatomy of the false pelvis is the downward continuation of the greater sac Osseous boundaries: wings of the ilia, superior rami of the pubic bones, L4 and L5 vertebrae Its lateral wall is formed in part by the iliacus, which fills the iliac fossa
Bony wall, ligaments and foramina
- Relatively unyielding framework: two os coxae (hip bones), the sacrum and the coccyx, with their ligaments Sacrum and coccyx bound the pelvis posteriorly; the hip bones anteriorly and laterally Piriformis and obturator internus arise from the bony surfaces of the true pelvis With their fascial coverings these muscles form the primary sections of the pelvic sidewall Bony foramina and their contents place secondary limits on the dimensions of the true pelvis
- Pelvic inlet is formed by the body and superior pubic rami with their pectineal lines, the arcuate lines of the ilia and the sacral promontory Pelvic outlet is formed anteriorly and laterally by the inferior pubic rami, pubic symphysis and pubic arcuate ligament Outlet is completed laterally by the rami and tuberosities of the ischia Ligaments, sacrum and coccyx complete it posterolaterally and posteriorly
- Top panel is the right posterior view of the pelvis with the sciatic nerve leaving below piriformis Inset is a right lateral internal view of the potential hernial sites A is a suprapiriformic sciatic hernia, above the piriformis B is an infrapiriformic sciatic hernia, below the piriformis C is a subspinous sciatic hernia through the lesser sciatic foramen
- Both ligaments participate in forming the pelvic walls They convert the greater and lesser sciatic notches into the greater and lesser sciatic foramina Sacrotuberous ligament: origin at the posterior superior iliac spine and lateral border of sacrum and coccyx; inserts on the ischial tuberosity Sacrospinous ligament: origin at the lateral border of sacrum and coccyx; inserts on the ischial spine Medial attachments are to sacrum and coccyx; lateral attachments to ischial tuberosity and ischial spine
- Five times larger than the lesser sciatic foramen Formed by conversion of the greater sciatic notch into a foramen by the sacrospinous ligament Transmits the piriformis muscle and the sciatic nerve Also transmits the gluteal and perineal vessels and nerves leaving the pelvis Piriformis divides it into suprapiriformic and infrapiriformic compartments
- Formed by conversion of the lesser sciatic notch into a foramen by the sacrotuberous and sacrospinous ligaments Obturator internus and the gemelli arise from the edges of the foramen and leave through it Pudendal nerve, internal pudendal vessels and the nerve to obturator internus pass through it to reach the perineum Suprapiriformic, infrapiriformic and lesser sciatic foramina are all potential sites of herniation
- Piriformis emerges through the greater sciatic foramen and separates it into two compartments Obturator internus fills the lateral wall and leaves through the lesser sciatic foramen Sacrospinous and sacrotuberous ligaments close the two notches into foramina Arcus tendineus of levator ani runs across the obturator fascia Coccygeus lies on the pelvic surface of the sacrospinous ligament
- B, Right gluteal region with sites of sciatic hernias. Gluteus maximus transected and reflected.
Layers of the pelvic sidewall
- Three anatomic layers of the pelvic sidewall
- Five surgicoanatomic layers
- Panel A shows the sequence from skin inward: skin, subcutaneous tissue, muscle, bone, muscle Deep to the bone lie the sacral plexus and internal iliac vessels Parietal layer of pelvic fascia separates muscle from the extraperitoneal tissue Peritoneum is the innermost layer of the pelvic wall The same sequence is met in reverse when dissecting from inside the pelvis
- B, Frontal section of pelvis showing fasciae of pelvic diaphragm, obturator fascia, and pudendal (Alcock's) canal.
First layer: pelvic peritoneum
- Several peritoneal folds are associated with the urinary bladder Folds thought to have a support function are called true ligaments Folds thought less supportive are called false ligaments The authors call this distinction arbitrary and unconvincing The important peritoneal ligaments are listed in the table that follows
- Ligaments of the Bladder
- Ligaments of the Bladder (continued)
- Lateral umbilical ligament is peritoneum over the inferior epigastric artery and vein It is a landmark for the ductus deferens at laparoscopic pelvic lymph node dissection It also locates inguinal structures during laparoscopic herniorrhaphy V marks the vein and A the artery in the illustration The vessels ascend medial to the deep inguinal ring
- Medial umbilical ligament is peritoneum over the obliterated umbilical artery, passing up and medially to the umbilicus Median umbilical ligament is peritoneum over the urachus and separates the two supravesical fossae Supravesical fossae lie above the apex of the bladder Paravesical fossae lie lateral to the bladder Transverse vesical fold separates paravesical from supravesical fossae and is most distinct when the bladder is empty
- Rectovesical fossa is the male counterpart of the pouch of Douglas It separates the rectum behind from the bladder and seminal vesicles in front Sacrogenital ligaments are the male counterparts of the uterosacral ligaments Rectal fascia and Denonvilliers' fascia are shown behind and in front of the rectum Ureter passes deep to the ductus deferens on its way to the bladder
- Vesicouterine pouch lies between the upper posterior bladder and the body and fundus of the uterus Broad ligaments extend laterally to the pelvic sidewall Uterosacral ligaments pass back from the cervix, embracing the rectum, raising the rectouterine folds Rectouterine pouch of Douglas separates uterus and posterior vaginal fornix from rectum and rectal ampulla Pararectal fossae lie between the uterosacral folds and the lateral wall of the rectal ampulla
- Peritoneum lies anterior to the fossa Behind it lie the bifurcation of the left common iliac artery and the left ureter entering the true pelvis Sigmoid mesocolon and its vessels, including the sigmoid artery, lie above and to the right Apex of the fossa is a landmark for finding the left ureter With a finger in the fossa the left ureter can be rolled on the underlying left common iliac artery
Second layer: blood vessels of the pelvis
- Arteries and veins of the pelvic wall and viscera lie between the peritoneum and the parietal pelvic fascia The two main vessels are the internal iliac artery and internal iliac vein (hypogastric artery and vein) In the upright position both run vertically along the pelvic sidewall Branches pass medially and inferiorly to reach the pelvic viscera They carry with them a heavy connective tissue mantle, the hypogastric sheath, which supports the organs
- Visceral internal iliac branches, visceral nerves, endopelvic connective tissue and smooth muscle form the second surgical layer It is within this layer that an injured visceral vessel is clamped, ligated or clipped Other pelvic arteries are the unpaired median sacral artery and the terminal inferior mesenteric artery The inferior mesenteric contributes sigmoid branches and the superior rectal artery All of these enter the pelvis retroperitoneally and all can be safely ligated
- Abdominal aorta bifurcates into the common iliac arteries at about L4, 1-2 cm below and to the left of the umbilicus In a thin supine patient the pulse can be palpated at the bifurcation and the external iliacs at the pelvic brim Inferior vena cava is formed from the two common iliac veins about 2-3 cm inferior to the umbilicus Common iliac artery divides into internal and external iliac at the pelvic brim, opposite the sacroiliac joint Less commonly the bifurcation lies just above or below the joint, especially with tortuous or diseased vessels
- Median sacral artery springs from the posterior aortic wall and is often forgotten by the surgeon Despite its small size it can bleed troublesomely when lacerated In some individuals its branches and the lateral sacral arteries ascend through the ventral sacral foramina These branches supply sacral and lumbar nerve roots They may even contribute to the arterial supply of the caudal spinal cord
- The right common iliac artery crosses in front of the left common iliac vein This relationship is thought to underlie the greater frequency of deep venous thrombosis of the left common iliac vein and left lower limb Inferior vena cava reflux with tricuspid regurgitation has been implicated in pelvic congestion syndrome Wohlgemuth et al. recommend percutaneous transluminal angioplasty, stenting or both for pelvic vein stenosis after surgical thrombectomy
- Internal iliac bifurcation and the rule of three
- Internal iliac artery divides into anterior and posterior divisions Superior gluteal artery passes through the superior part of the greater sciatic foramen Inferior gluteal artery enters the foramen below the piriformis Superior and inferior vesical arteries and the obturator artery arise before the foramen is entered Median sacral and superior rectal arteries are unpaired and are not shown All these arteries enter the pelvis extraperitoneally and may be ligated with impunity
- Three parietal branches: iliolumbar, superior gluteal and lateral sacral arteries Iliolumbar artery lies behind the obturator nerve and runs deep and laterally under psoas to supply iliacus and the iliac fossa Superior gluteal artery is related to the sacral plexus It usually passes between the lumbosacral trunk and the ventral ramus of S1 at the upper border of piriformis There are one to three lateral sacral arteries, lying in front of the sacral plexus
- Superficial branch of the superior gluteal artery supplies the upper half of gluteus maximus Deep branch runs transversely between gluteus medius and minimus, supplying both Both branches anastomose extensively with the inferior gluteal, medial circumflex and lateral femoral circumflex arteries Inferior gluteal artery, usually a terminal branch of the anterior division, may leave the pelvis between S1 and S2 It supplies about the lower half of gluteus maximus and anastomoses richly deep to that muscle In a significant number of individuals the inferior gluteal and obturator arteries arise from the posterior division
- Obturator artery lies below the obturator nerve at the pelvic sidewall and leaves through the obturator foramen In about 20 percent of individuals it arises from the superior gluteal artery In 33 percent or more an aberrant or accessory obturator artery arises from the inferior epigastric artery The aberrant vessel is closely related to the lacunar ligament of Gimbernat It crosses medial to, lateral to, or directly over the femoral ring and Cooper's ligament
- Schematic of the right side of the pelvis Position 1 marks the normal obturator vessel arising from the internal iliac system Position 2 marks the variant vessel crossing the superior pubic ramus from the inferior epigastric system The variant vessel crosses the pelvic brim at the site of femoral hernia repair Both may coexist, with anastomoses at the obturator canal
- Gilroy et al. reported an artery, vein or both in the variant position in 70-82 percent of pelvic halves The same study found a variant vessel in 83-90 percent of whole pelves Arteries were found predominantly in the normal position only Normal and anomalous veins were most frequently found together It is therefore far more common than not to find a vessel crossing the pelvic brim at this site
- Schematic summarizing the most common pattern for obturator arteries and veins with the range of percentages from the United States and China in parentheses.
- Summary schematic of the likelihood of encountering a variant obturator vessel on an individual pelvic side.
- Internal pudendal artery is the more anterior of the two terminal branches of the anterior division It leaves the pelvis through the greater sciatic foramen and crosses the sacrospinous ligament just medial to the tip of the ischial spine Artery and vein lie lateral to the pudendal nerve as they exit below piriformis It re-enters through the lesser foramen into Alcock's canal to supply the ischioanal fossa and urogenital structures An accessory pudendal artery often arises just before the internal pudendal leaves the pelvis It occurs in about 10 percent of males and passes beneath the pubic arcuate ligament to the deep dorsal vein of the penis or clitoris
- Middle rectal artery arises most commonly from or with the vesical, internal pudendal or inferior gluteal arteries It may also arise directly from the anterior division of the internal iliac, or from the uterine artery Its three characteristic features caused Last to state that it is inappropriately named Uterine artery crosses the pelvic floor in the parametrial tissue of the broad ligament It arises most commonly from the same vascular stem as the umbilical artery Vaginal artery is often a separate branch of the internal iliac, or arises from the uterine artery; there may be more than one
- Uterine artery passes medially towards the uterine isthmus, crossing over the ureter The crossing is water under the bridge, about 1.5 cm from the cervix, varying from 1 to 4 cm At the cervix the uterine artery turns upward on the lateral wall of the uterine body It anastomoses end on with the tubal branch of the ovarian artery at the uterotubal junction Uterine artery is the principal supply to the uterine tube in about 60 percent of cases Male homologue of the uterine artery is the deferential branch of the inferior vesical artery
- Identify the obliterated portion of the umbilical artery where it passes the bladder Trace it proximally toward its origin from the anterior division of the internal iliac Identify the superior vesical branch passing medially toward the bladder Continue proximally to identify the uterine artery arising from the same vascular stem Follow the uterine artery medially toward the uterine isthmus and note it crossing over the ureter
- Any artery leaving the pelvis may be ligated with relative impunity if its accompanying nerves are spared Occlusion of the internal iliac at its origin, or ligation of both gluteal arteries, can cause gluteal ischaemia The chapter lists eight potentially major collateral pathways after bilateral internal iliac ligation Anastomosis of the middle rectal with the superior rectal artery, and of their veins, can be extensive and significant Superior rectal artery is the terminal continuation of the inferior mesenteric artery
- Superior rectal artery is the downward continuation of the inferior mesenteric artery It touches but does not cross the medial side of the left ureter It crosses the bifurcation of the left common iliac vessels and descends in the sigmoid mesocolon Middle rectal artery anastomoses with the superior rectal artery, and their veins with each other Superior rectal vein drains to the inferior mesenteric vein and so to the portal system Middle and inferior rectal veins drain to the systemic circulation
- Multiple small veins from the rectal plexus form the superior rectal vein, draining to the inferior mesenteric vein and the portal system Other rectal veins combine to form the middle rectal vein Superior and inferior gluteal veins emerge through the suprapiriformic and infrapiriformic apertures and form the internal iliac vein Uterine, vesical or prostatic plexus veins unite with the middle rectal vein to join the internal iliac vein Internal pudendal vein emerges through the lesser sciatic foramen to join the inferior gluteal or internal iliac vein There are many variations of pelvic venous drainage
- Veins of female pelvis.
- Venous pathways.
- Right and left ovarian veins and branches of internal iliac vein.
- Batson's vertebral venous plexus and pelvic metastasis
- Vertebral system of veins.
- Lymphatic drainage of the pelvic organs follows the arteries that supply them The table that follows lists each organ or organ part with the nodal group receiving its lymph Note where drainage changes within a single organ, as in the uterus, vagina, bladder and anal canal The pectinate line of the anal canal is the classic watershed Structures draining to the superficial inguinal nodes are those derived from or covered by perineal skin
- Lymphatic Drainage of Pelvic Organs
- Lymphatic Drainage of Pelvic Organs (continued)
- Lymphatic Drainage of Pelvic Organs (continued)
- Lymphatic Drainage of Pelvic Organs (continued)
Third layer: pelvic fasciae
- Last described it as a strong membranous layer covering the obturator internus and piriformis muscles It is firmly attached to the periosteum at the muscle margins The authors extend it to include the fascia covering the pelvic surface of levator ani and coccygeus This is consistent with the endoabdominal fascial lining being a continuum, the fascia transversalis That continuum runs from the inferior surface of the respiratory diaphragm to the pelvic basin, sidewalls and floor Parietal fascia of the pelvic basin is continuous with that of the false pelvis above
- Visceral fascia is the connective tissue that encapsulates the individual pelvic organs It is named for the organ it covers: vesical, rectal or prostatic Its thickness varies greatly between organs Where an organ passes through the pelvic floor, the visceral capsule fuses with the parietal fascia of the floor Density conforms to the distensibility of the organ: loose over bladder and rectum, dense over prostate The investing fascia contains the collecting lymphatic channels draining the organ
- Prevesical, prevaginal and rectovaginal layers are shown as distinct fascial laminae Main sheet of fascia runs from the sacrum forward across the pelvic floor Uterosacral fold is raised by the underlying uterosacral ligament Levator ani lies below the fascial sheet, with the perineal body anteriorly Fascial layers are named for the organ surface they cover
- Beginning anteriorly at the pubic bones there is a continuous mantle of felt-like connective tissue and smooth muscle It is called the pubocervical, pubovesical or pubovesicocervical fascia It covers the anterior vaginal wall and joins the superior fascia of the pelvic diaphragm lateral to the vagina or prostate There it forms a bilateral band from about 1 cm above the lower border of the pubic bone to the ischial spine This band is the arcus tendineus fascia pelvis, the white line of the pelvis The mantle is continuous with the visceral fascia encapsulating the individual organs
- Cross section taken through the vagina with the bladder and rectum on either side Tendinous arch of the pelvic fascia is the white line or fascia arcus Tendinous arch of levator ani is a separate, more lateral line on the obturator fascia The two arches must be distinguished from one another Rectovaginal fascia of Denonvilliers lies behind the vagina Coccygeus and iliococcygeus complete the floor posterolaterally
- Connective tissues between peritoneum, visceral capsules and parietal fascia are organised into predictable forms Their density and quantity vary with age, sex, state of health and obesity Nomenclature and interpretation of these bands and visceral ligaments lack unanimity in the literature Condensations of connective tissue and smooth muscle accompany the vessels and nerves supplying the pelvic organs The authors group them as a vascular leash and a neural leash to the viscera
- One major band extends from and incorporates the branches of the internal iliac vessels to the midline pelvic organs The authors compare it to a vascular leash to the viscera It appears comparable with Uhlenhuth's hypogastric wings The cardinal ligament is part of this complex and accompanies the uterine artery It is also called the lateral cervical ligament, transverse cervical ligament, retinacula uteri or ligament of Mackenrodt Anteriorly the lateral pillar of the bladder derives from the same tissue and continues upward with the obliterated umbilical artery
- A second condensation is formed largely by presacral connective tissue with contributions from piriformis fascia It incorporates splanchnic nerve branches from the sacral plexus and elements of the pelvic (inferior hypogastric) plexus The authors liken it to a neural leash for the viscera Nerve elements plus connective tissue, smooth muscle and overlying peritoneum form the uterosacral ligaments Left pelvic rectal stalk is thicker than the right: it carries the ascending parasympathetic fibres to descending and sigmoid colon
- Muntean described the presacral fascia as continuous with the lateral pillars of the rectum and with the arcus tendineus fascia pelvis This forms a hammock-like support for the rectum Presacral fascia initially invests the pelvic splanchnic nerves and then the right and left pelvic plexuses The forward extension of presacral fascia, the fascia of Waldeyer, is continuous with the lateral pillar of the rectum It receives the superior and middle rectal vessels and their fasciae Beneath the peritoneum of the pararectal fossa this band is evident as the uterosacral ligament
- Anterior to the cul de sac of Douglas the presacral band splits: part continues as the uterosacral ligament and part as the rectovaginal septum The bilaminar rectovaginal septum of the female separates rectum from posterior vaginal wall The bilaminar rectogenital septum of the male separates rectum from prostate anteriorly The septum extends from one ischial spine to the other and is attached inferiorly to the perineal body and pelvic floor The potential space of Proust lies between its two laminae, facetiously called the space between wind and water It is derived from the original attachment of peritoneum to the pelvic floor, lifted as the organs grew
- Vesicoumbilical fascia is a triangular condensation of extraperitoneal connective tissue from bladder to umbilicus The urachus lies in the middle of the triangle and the obliterated umbilical arteries laterally Variable adipose tissue is incorporated between its anterior and posterior laminae, lying between peritoneum and transversalis fascia In the upright position bladder, anteflexed uterus, most of the vagina and the rectal ampulla lie in horizontal planes These organs are suspended by hammock-like connective tissue extending from one side of the pelvis to the other At the level of the ischial spine the vascular and neural leashes converge with the arcus tendineus fascia pelvis
Fourth layer: nerves of the pelvis
- Havenga et al. define them as the paired sympathetic hypogastric nerve, the sacral splanchnic nerves and the pelvic autonomic plexus Their anatomy is closely related to the fascial planes forming the retrorectal space The rectum is surrounded by fatty tissue containing its vessels, lymphatics and lymph nodes: the mesorectum Bladder and sexual dysfunction after rectal cancer surgery can be avoided in most cases by identifying and preserving these nerves This depends on teaching surgeons the anatomy of the pelvic autonomic nerves and the pelvic fascial planes
- Pelvic nerves include branches of the lumbar and sacral plexuses, the abdominal sympathetics and sensory fibres Visceral nerve elements supply the pelvic organs with autonomic and visceral afferent fibres Parietal neural structures include the obturator nerves, lumbosacral plexus and coccygeal plexus and their derivatives Innervation of visceral peritoneum is poorly localised It is carried by nerves whose principal function is sympathetic Pain is referred to the body wall levels matching the cord segments entered: T11 to L2 serves most of the lower abdomen and pelvis
- Pelvic plexuses are best seen in the endopelvic tissues of the pelvic sidewall They contain a mixture of parasympathetic and sympathetic ganglia They lie lateral to the rectum within the endopelvic and visceral fasciae, mixing sensory and autonomic fibres The term inferior hypogastric plexus is as unsatisfactory as hypogastric artery for the internal iliac, but is fixed in clinical use Hypogastric nerves lie at the lateral pelvic wall, 1-2 cm medial to and parallel with the ureter They bridge the superior hypogastric plexus and the pelvic plexus
- Superior hypogastric plexus lies at the aortic bifurcation and has no named ganglia It can be considered the continuation of the preaortic plexus beyond its inferior mesenteric part It divides into the right and left pelvic (inferior hypogastric) plexuses The hypogastric nerves originate in this plexus When ligating the inferior mesenteric artery, take care not to violate the plexus and the left hypogastric nerves The authors advise careful isolation of the artery before ligation
- Sympathetic fibres are vasomotor, motor to sphincters, inhibitory to peristalsis and sensory for pain from most pelvic viscera Smooth muscle of the vesical trigone and the internal urethral sphincter is supplied through the hypogastric (presacral) sympathetic nerves Testes and ovaries have good sympathetic supply but no demonstrable parasympathetic supply The sympathetic contribution comes largely from the hypogastric plexus in front of the body of L5 Additional branches arise as sacral splanchnic nerves from the sacral sympathetic chains Sacral splanchnic nerves must not be confused with the parasympathetic pelvic splanchnic nerves
- Sacral sympathetic trunks cross the pelvic brim just behind the common iliac artery and vein They run down close to the concavity of the sacrum, in most cases medial to the anterior sacral foramina The foramina are useful landmarks for the topography of the trunks The two chains meet anterior to the coccyx and unite as the ganglion impar All sacral ventral primary rami receive grey communicating rami from the sympathetic trunks
- Parasympathetic part of the pelvic plexus derives from S2 to S4: the pelvic splanchnic nerves or nervi erigentes They are motor and secretomotor to the gut from the splenic flexure to the rectum They innervate the detrusor muscle of the bladder and the muscle of the rectum They supply the smooth muscle of the internal anal sphincter Erectile tissue of the penis and clitoris receives its functional fibres for erection from these nerves
- Schematic transverse section of the male pelvis at the level of the rectum Mesorectum surrounds the rectum within its fascia propria Most of the pelvic nerve plexus is laterally embedded in endopelvic fascia on the pelvic wall Middle rectal artery is separated from the lateral ligaments Presacral fascia and presacral veins lie behind Hypogastric nerve and nervi erigentes lie on the sidewall
- Male pelvis showing fascia in front of and behind rectum (schematic sagittal section). Dotted lines represent paths of incisions in abdominoperineal resection for cancer. Note the incision of anterior peritoneum in front of fascia of Denonvilliers. Fascia of Denonvilliers is incised lower down, opposite seminal vesicles. Rectosacral fascia is incised posteriorly, disconnecting rectum from hollow of sacrum.
- Obturator nerve arises from the anterior divisions of L2 to L4 It is the chief nerve supply of the adductor compartment of the thigh Motor to obturator externus, adductor longus, adductor brevis, adductor magnus (anterior part) and gracilis Anterior division supplies adductor longus and gracilis; posterior division supplies adductor brevis and magnus Sensory to the intermediate part of the medial surface of the thigh, with some fibres to the knee joint It traverses the pelvis only through extraperitoneal fatty tissue
- Nerve is formed from L2, L3 and L4 and descends to the obturator foramen Articular branch is given to the hip joint before the canal Anterior division supplies pectineus, adductor longus, adductor brevis and gracilis Posterior division supplies obturator externus and adductor magnus An articular branch is given to the knee joint distally
- Pellegrino and Johnson reported bilateral obturator nerve injury after prolonged urologic surgery The injury was believed to result from stretching at the bony obturator foramen Ali reported a left tubal ectopic pregnancy presenting with left obturator nerve pain The authors consider referral to the L2 dermatome, which the obturator nerve supplies in part, the more likely explanation Accessory obturator nerve, when present, passes over the superior pubic ramus and behind the femoral sheath It supplies the pectineus muscle
- Lumbosacral plexus is formed by the lumbosacral trunk and the anterior primary rami of L4 to S5 L4 is shared by both lumbar and sacral plexuses; its furcal nerve joins L5 as the lumbosacral trunk Sacral nerves emerge from the anterior sacral foramina and unite in front of piriformis Superior gluteal nerve is L4 to S1 and inferior gluteal nerve L5 to S2 Sciatic nerve is L4 to S3 and pudendal nerve S2 to S4 Posterior femoral cutaneous nerve is S1 to S3
- Lumbosacral plexus (L4-S5) is formed in the posterior wall of the pelvis Several branches supply the pelvic viscera as the pelvic splanchnic nerves Other branches innervate the muscles of the pelvic floor and sidewalls Motor branches lie deep to the endopelvic fascia and exit via the greater sciatic foramen The nerve to levator ani is the exception and does not leave the pelvis Branches exiting the foramen include the pudendal nerve, the gluteal nerves and the sciatic nerve
- Course of the pudendal nerve
- Three divisions: inferior rectal, perineal, and the dorsal genital nerve of the penis or clitoris Inferior rectal nerve supplies the external anal sphincter, assists levator ani, and supplies perianal skin and anal mucosa below the pecten Perineal branch divides into posterior scrotal or labial cutaneous branches and deep muscular branches Deep muscular branches supply the muscles of the superficial and deep perineal pouches Dorsal nerve supplies the glans, prepuce and skin of the penis and spongy urethra, or the clitoris Five territories: pelvic, pudendal, deep perineal pouch, dorsum of penis or clitoris, and gluteal
- Alcock's canal (dotted) and its contents.
- Alcock's canal (formed by pelvic fascia and fascia lunata).
- L1 supplies the anterior scrotum or vulva; S3 supplies the posterior scrotum or vulva In some individuals most of the sensory fibres to the perineum come from the posterior femoral cutaneous nerve In such cases a pudendal nerve block may not achieve complete anaesthesia Large muscles of the lower limb are almost always supplied by two or more spinal nerve levels Pudendal and sciatic nerves are the terminal branches of the sacral plexus
- A, Male.
- B, Female.
- Superior gluteal nerve passes through the suprapiriformic part of the greater sciatic foramen Inferior gluteal nerve, posterior cutaneous nerve of thigh and sciatic nerve pass through the infrapiriformic part Lesser sciatic foramen transmits the pudendal nerve and the nerve to obturator internus Internal pudendal artery and vein also traverse the lesser sciatic foramen Gluteus maximus and medius have been reflected to expose the exits
- Right pelvic wall and nerve supply. Sacral and coccygeal plexus. Inset: Course of pudendal nerve.
- Diagrammatic representation of the course of the sciatic nerve and the common peroneal and tibial nerves, and the nerve to the hamstring muscles.
Fifth layer: muscles and the obturator region
- Pelvic muscles divide into lateral pelvic muscles and the muscles of the pelvic diaphragm The lateral pelvic muscles are the piriformis and the obturator internus Within the pelvis piriformis is related to the rectum, sacral plexus, internal iliac branches and, inferiorly, the coccygeus Outside the pelvis it is related to the posterior surface of the ischium, the hip joint capsule and gluteus maximus Iliacus forms part of the lateral wall of the false pelvis and fills the iliac fossa The authors exclude psoas major and minor from the pelvic sidewall musculature
- Pelvic surface of obturator internus forms the lateral boundary of the ischioanal fossa of the perineum The fossa is fat-filled and pyramid-shaped on either side of the anus Outside the pelvis obturator internus is joined by the superior and inferior gemelli from the margins of the lesser sciatic foramen It is then covered by gluteus maximus and crossed by the sciatic nerve Tendinous arch of levator ani is a specialisation of the obturator fascia running from ischial spine to the body of the pubis It gives origin to the lateral part of pubococcygeus and the whole of iliococcygeus
- View from within the abdomen looking down on the pelvic floor Levator ani is attached laterally to the arcus tendineus Urethra and bladder lie anteriorly in the midline Obturator canal and obturator internus lie on the lateral wall The muscle sheet slopes down and forward from the arch to the midline viscera
- An obturator hernia is protrusion of preperitoneal fat or an intestinal loop through the obturator canal It characteristically affects the right side of middle-aged women Obturator region is bounded above by the superior pubic ramus and laterally by the hip joint and femoral shaft Medially it is bounded by the pubic arch, the perineum and gracilis Inferiorly it is bounded by the insertion of adductor magnus on the adductor tubercle
- Lateral view of the right side of the pelvis showing the three hernial sites Inguinal hernia is the most common and the anatomically weakest site Femoral hernia is less common and anatomically less weak Obturator hernia is rare and the anatomically least weak site Pectineus lies over the obturator site and must be divided or retracted for exposure
- Obturator foramen is the largest bony foramen in the body, formed by the rami of the ischium and pubis It lies inferior to the acetabulum on the anterolateral wall of the pelvis Except for the obturator canal the foramen is closed by the obturator membrane Membrane fibres are continuous with the periosteum of surrounding bone and with the tendons of the internal and external obturator muscles Embryologically the foramen represents an area of potential bone formation that never completes In this sense the foramen is a lacuna and the obturator canal is the true foramen
- View of the medial wall of the male pelvis showing the obturator canal and its contents Obturator canal is a tunnel 2 to 3 cm long beginning at the defect in the obturator membrane It runs obliquely downward to end in the obturator region of the thigh Bounded above and laterally by the obturator groove of the pubis Bounded inferiorly by the free edge of the obturator membrane and the obturator muscles Transmits the obturator artery, vein and nerve, and the hernial sac when present
- C, Diagrammatic coronal section of the lateral wall of the male pelvis showing the relation of obturator nerve, artery, and vein to other pelvic structures.
- The obturator nerve is usually superior to the artery and vein in the canal The nerve separates into anterior and posterior divisions as it leaves the canal A hernial sac may follow either division of the nerve into the thigh The obturator artery divides to form an arterial ring around the foramen In the majority of cases the obturator artery provides the artery to the head of the femur
- Long section of the upper thigh through the obturator foramen Hernia may follow the anterior division of the obturator nerve It may alternatively follow the posterior division Anterior route places the sac in front of adductor brevis, deep to pectineus and adductor longus Posterior route places the sac behind adductor brevis and in front of adductor magnus Peritoneum, obturator internus, obturator membrane and obturator externus are crossed in turn
- Sagittal section of thigh showing the course of obturator hernia (dashed arrows) along obturator nerve and its branches.
- F, As it emerges through the obturator canal, the obturator artery divides to form an arterial ring around the obturator foramen.
- Repair may be abdominal, retropubic, obturator, inguinal, laparoscopic, or a combination Choice of approach depends on whether the diagnosis is certain With a certain diagnosis the authors advise a lower suprapubic transverse incision Without a certain diagnosis they advise a lower midline incision
- The most important principle of curative surgery is total resection of the mesorectum Dissection must be careful, deliberate and haemostatic along the parietal pelvic fascia To mobilise the rectum fully and treat most midrectal cancers the rectovaginal septum must be dissected This creates a rectovaginal space down to the pelvic floor Boundaries of the rectovaginal space: pouch of Douglas cranially, perineal body caudally, pararectal spaces laterally Iatrogenic injury has become the most common cause of genitourinary trauma
Pelvic floor: form and orientation
- Pelvic floor is composed of musculature, erectile tissues and connective tissues of the perineum below Above it lie the pelvic diaphragm and its superior and inferior fasciae The perineal membrane is part of the connective tissue component By convention the floor is described with the organs of the true pelvis and the perineum separately The authors argue this artificial separation adds to the confusion of students and practitioners Musculofascial pelvic floor and the perineum are closely related embryologically, structurally and functionally
- Hip bone shown in its true standing orientation The top of the bone contacts the vertical bar at the anterior superior iliac spine The bottom contacts the same vertical bar at the pubic tubercle Anterior superior iliac spine and pubic tubercle therefore lie in the same vertical plane Smaller bars mark the approximate boundaries between the three bones of the os coxae
- When standing, the anterior superior iliac spines and the pubic tubercles lie in the same vertical plane Most modern anatomy texts acknowledge this Yet illustrations in many of the same texts show an error of almost 60 degrees in orientation They often label the true anterior view as a superior view Stromberg and Williams documented this misrepresentation
- Upper, Commonly presented, but incorrect, "front view" of bony pelvis, rotated about 60° to 75° from proper position. Lower, Similar incorrect view of bony pelvis, originally published in 1801.
- Properly oriented bony pelvis with proximal femora attached (front view). Note that most of sacrum recedes from observer. Compare to Fig 28-33.
- Because the pelvic inlet is relatively vertical, the symphysis and much of the ventral sacrum face essentially downward The long axis of the symphysis slopes downward at about 30 degrees to the horizontal in the female, slightly more in the male The ischiopubic ramus essentially parallels the ground Much of the pressure and weight of the abdominopelvic organs is directed toward the urogenital triangle The urogenital muscular and fascial elements between the ischiopubic rami undergird the pelvic diaphragm They provide essential assistance to its role in support and in pelvic visceral function
Pelvic diaphragm and levator ani
- Pelvic diaphragm provides a musculofascial floor for the true pelvis It is complete except for the midline openings between the two halves: the urogenital hiatus and the rectal hiatus Rectum, urethra and vagina pass through it together with the fascia of levator ani It is composed of two paired muscles, the levator ani and the coccygeus Anteriorly, between the inferior pubic rami, the floor is reinforced by the urethrogenital complex including the urogenital diaphragm Integrity of pelvic organ support depends on this complex of structural features
- Coronal section of male pelvis illustrating main part of funnel-shaped pelvic diaphragm formed mainly by two levator ani muscles. Pelvic diaphragm forms floor of abdominal and pelvic cavities and consists of paired levator ani and coccygeus muscles with their superior and inferior fasciae. Rectum is anchored to pelvic diaphragm in middle (see Fig. 28-41). Only pelvic diaphragm (levator ani portion) intervenes between ischioanal fossa and retropubic space.
- They arise from the ischial spine, the white line (arcus tendineus) of the obturator fascia and the body of the pubis They insert into the coccyx, the anococcygeal raphe, the perineal body and the midline viscera The musculature produces a gutter-like formation that slopes forward and downward Levator ani is made up of three contributing muscles: iliococcygeus, pubococcygeus and puborectalis Puborectalis is essential to maintaining rectal continence Shafik considers the puborectalis part of the external sphincter rather than of the levator ani
- Levator ani is composed of puborectalis, pubococcygeus and iliococcygeus Puborectalis is the most medial and forms a sling behind the anorectal junction Pubococcygeus lies lateral to it, running from the pubis backward Iliococcygeus is the most posterolateral, arising from the arcus tendineus Fibres converge on the anococcygeal raphe and the coccyx Perineal body lies anteriorly in the midline, between urethra and anus
- Iliococcygeus arises from the arcus tendineus levator ani, a specialisation of the obturator and levator fasciae It inserts into the midline raphe and upon the coccyx Posterior edge of pubococcygeus may be separated from the thinner, aponeurotic iliococcygeus by a narrow aponeurosis, or continuous with it Striated muscle between coccyx and rectum, including iliococcygeus and the posterior part of pubococcygeus, forms the levator plate Strength of the levator plate and its angulation to the horizontal matter for faecal continence The plate also prevents prolapse of the upper vagina, uterus and rectum
- Floor of the pelvis seen from above showing the levatores ani Iliococcygeus, pubococcygeus and puborectalis are labelled around the hiatus Coccygeus completes the floor posteriorly Inset shows how the anorectal junction is angulated by the puborectalis sling The sling pulls the anorectal junction forward toward the pubis Loss of the sling straightens the anorectal angle
- Medial borders of pubococcygeus form the lateral borders of the urogenital hiatus; puborectalis takes a more lateral course Delancey and Starr: vaginal wall and paraurethral smooth muscle, collagen and elastic fibres interdigitate with the medial levator fibres This occurs near the proximal urethra and extends from the ureteric orifices down to the urogenital diaphragm The inseparable vagina and lower urethra with their lateral levator attachments let the medial levator control the position of the vesical neck Mostwin observed that disruption of pubococcygeus attachments to the vaginal wall can cause herniation with secondary posterior bladder descent Oelrich found that pubococcygeus has no attachment to the coccyx
- Puborectalis arises from the lower posterior surface of the pubic bone It lies lateral and external to the pubovaginalis (levator prostatae) and pubococcygeus Some deeper fibres arise from fibrous tissue between it and the sphincter urethrae, supporting a levator influence on urethral function Left and right puborectalis fibres pass posteriorly and join behind the rectum as a well-defined sling They blend with and pass external to the more cranial part of the deep external sphincter Puborectalis forms the anorectal ring with the superficial and deep external sphincter and the proximal internal sphincter
- Coccygeus arises from the spine of the ischium and the pelvic surface of the sacrospinous ligament, overlapping it somewhat It inserts on the lateral aspects of the lower two sacral vertebrae and the upper two coccygeal vertebrae The funnel shape of the pelvic floor and anal canal provides discriminatory continence of gas, liquid and solid Many of the physiologic factors involved are poorly understood Two diaphragms are conventionally described at the pelvic outlet, the pelvic and the urogenital In fact these are more closely related anatomically and functionally than most sources recognise
- Sphincter urethrae, the other perineal muscles and the external anal sphincter arise from the cloacal sphincter and form an accessory pelvic diaphragm Levator ani arises from the caudal musculature, which moves the tail in lower animals and is modified in humans for support Levi et al. argue puborectalis is part of levator ani, citing common embryologic origin with pubococcygeus and iliococcygeus Cherry and Rothenberger state puborectalis is anatomically, neurologically and functionally merged with the deep external sphincter Pelvic diaphragm is supplied on its pelvic surface by the nerve to levator ani, from the ventral primary ramus of S4 or S5 A perineal branch may pierce and supply coccygeus and then the external anal sphincter
- A, Seen from above.
- B, Seen from below.
- A, Seen from above.
- B, Seen from below.
- Female pelvis (paramedian section).
Fasciae of the floor, perineal body and perineal hernia
- The three forms of fascia associated with the pelvic floor are parietal, visceral and diaphragmatic Parietal fascia is largely the fascia of obturator internus, piriformis and the pelvic diaphragm muscles It is seemingly interrupted within the pelvis by the narrow band of origin of levator ani It continues below that origin to form the lateral boundaries of the perineum There it forms Alcock's canal at the lateral wall of the ischioanal fossa, covering obturator internus Diaphragmatic fascia covers the superior (supraanal) and inferior (infraanal) surfaces of the pelvic diaphragm
- Visceral fascia is continuous with the endopelvic connective tissue between peritoneum and parietal fascia It invests almost all pelvic surfaces of the pelvic organs, possibly excepting parts of the fundus of the uterus and bladder It is continuous with the connective tissue sheaths of the nerves and vessels supplying the organs Superior layer of the urogenital diaphragm is continuous at its peripheral edges with the pelvic parietal fascia over the pelvic diaphragm The inferior fascia, the perineal membrane, is perhaps a different embryologic entity From a surgical standpoint this embryologic question does not affect function in health or disease
- In the male the perineal body is the central tendinous point, a bolus of tissue between the anus and the bulb In the female it is the perineum of the gynaecologist, a fibromuscular mass between the anus and the vagina It lies under the pelvic floor and is formed by the attachments of several muscles It is a midline landmark between the anterior and posterior triangles of the perineum It gives some support to the levator ani and thus to the pelvic organs It is larger and contains more muscle in the female than in the male
- Sagittal section through the female perineum with the perineal body shown in light grey It lies between the posterior vaginal wall in front and the rectum behind Above it the vaginal and urethral walls are fused Below and in front lies the vestibule It is larger and contains more muscle in the female than in the male
- A, Its formation by several muscles, from below.
- A perineal hernia is protrusion of a viscus through the pelvic diaphragm into the perineum, with a hernial sac It may be primary, or secondary to pelvic surgery; only primary hernias are considered here It is among the rarest of human hernias Unlike inguinal hernia, which seems related to the erect posture, perineal hernia is more common in quadrupeds than in humans By definition the pelvic diaphragm is the floor of the pelvic basin and the roof of the perineum A sac passing through any abnormal opening in the diaphragm will eventually appear in the perineum
- A primary perineal hernia may occur anterior or posterior to the superficial transverse perineus muscle Anterior hernia passes through the pelvic and urogenital diaphragms, lateral to bladder and vagina and anterior to the urethra It has been called pudendal, labial, lateral or vaginal-labial, and is found only in women Posterior hernia passes between components of the pelvic diaphragm or through the hiatus of Schwalbe, lateral to urethra, vagina and rectum The hiatus of Schwalbe is formed by non-union of the obturator internus and levator ani muscles Two posterior sites: upper, between pubococcygeus and iliococcygeus; lower, between iliococcygeus and coccygeus below the gluteus maximus margin
- Female perineum seen from below with the sites of perineal hernia marked Anterior perineal hernia protrudes through the urogenital diaphragm It enters the triangle bounded by bulbospongiosus medially, ischiocavernosus laterally and superficial transverse perineus inferiorly Posterior perineal hernia emerges between levator ani muscle bundles, or between levator ani and coccygeus The posterior site lies midway between the rectum and the ischial tuberosity Anterior hernias occur only in females
- B, Boundaries of the perineum seen from above. This diamond-shaped area can be divided by a line connecting the ischial tuberosities into an anterior or urogenital triangle and a posterior or anal triangle.
- In males the perineal hernia enters the ischioanal fossa In females it may enter the fossa or the labium majus It may also lie close to the vaginal wall, or below the lower margin of gluteus maximus A perineal hernia may be approached for repair through the perineum or through the abdomen Anatomic complications of the pelvic floor are the complications of surgery on the structures related to it
Summary and sources
- Landmarks worth carrying into theatre
- Three hernias of the pelvic wall and floor
- Nerves at risk in pelvic surgery
- Sources cited in the text
- Sources cited in the text (continued)
- Sources cited in the text (continued)
- Sources cited in the text (continued)
- Skandalakis' Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery
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