This chapter should be cited as follows:
Centini G, Cannoni A, et al., Glob Libr Women's Med
ISSN: 1756-2228; DOI 10.3843/GLOWM.420273

The Continuous Textbook of Women’s Medicine Series – Gynecology Module

Volume 8

Gynecological endoscopy

Volume Editors: Professor Alberto Mattei, Director Maternal and Child Department, USL Toscana Centro, Florence, Italy
Dr Federica Perelli, Obstetrics and Gynecology Unit, Ospedale Santa Maria Annunziata, USL Toscana Centro, Florence, Italy

Chapter

Surgical Anatomy of the Pelvis

First published: September 2023
Updated: July 2026

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INTRODUCTION

Pelvic anatomy may be described according to different anatomical concepts, depending on the purpose of the description. These include surgical, functional and topographical anatomy, as well as the anatomy of specific organs and systems, including the neurovascular anatomy of the pelvis.

Although pelvic anatomy has been studied for centuries, the advent of minimally invasive surgery has enabled surgeons to examine living tissues under magnification, providing new insights into anatomical relationships that are less apparent during open surgery.

This chapter aims to provide the basic anatomical knowledge required to perform pelvic surgical procedures. It describes the key anatomical structures and provides practical guidance on developing the pelvic spaces and identifying the important structures that should be preserved during surgery.

PELVIC MUSCLES AND FASCIAS 

Muscles

The central muscular element of the pelvis is represented by the pelvic floor (or pelvic diaphragm), consisting of levator ani muscle and coccygeus muscle, covered by pelvic fascia.¹ The levator ani muscle consists of three different parts: the pubococcygeus, iliococcygeus and puborectalis.

The pelvic floor has two hiatuses: (1) anterior urogenital hiatus, through which the urethra and vagina pass, and (2) the posterior rectal hiatus, through which the anal canal passes. The pelvic floor divides the pelvic cavity from the perineal region, which is located caudally.

The pelvic floor is essential for providing support to the pelvic organs and for maintaining urinary and bowel continence, as it forms part of the urinary and anal sphincter mechanisms.²

The pubococcygeus muscle, shaped like a hammock, is the main component of levator ani muscle and arises from the pubic bone and is directed dorsally towards the coccyx. Some of its fibers are directed towards the urethra and the vagina. The puborectalis muscles arise from the lower part of the pubic symphysis and run caudally and dorsally to conjoin behind the anorectal junction, forming a muscular sling. The iliococcygeus muscle represents the dorsal and lateral part of levator ani muscle; it arises from the ischial spine and is directed towards the lower segment of the coccyx. The coccygeus muscle lies posterior to the levator ani and extends from the ischial spine to the lateral margins of the lower sacrum and coccyx.

Another important muscle of the pelvis is the obturator internus, which originates from the internal surface of the obturator membrane and the surrounding margins of the obturator foramen, including the pubis and ischium.³ It exits the pelvis through the lesser sciatic foramen and inserts onto the greater trochanter of the femur. Through its fascial attachments, it also contributes to support of the pelvic viscera, including the urinary bladder. The posterior and lateral boundaries of the pelvis are formed in part by the piriformis muscle, a flat, pyramidal-shaped muscle that originates from the anterior surface of the sacrum and the superior margin of the greater sciatic notch. It leaves the pelvis through the greater sciatic foramen and inserts onto the greater trochanter of the femur. Piriformis muscle is an important anatomic landmark because it divides the greater sciatic foramen into superior and inferior compartments.

The levator ani has a funnel-shaped configuration, with an anterior opening formed by the urogenital and anal hiatuses. This region represents the weakest part of the pelvic floor and is therefore most susceptible to pelvic organ prolapse.⁴ The puborectalis muscle contributes to closure of the levator hiatus by drawing the anorectal junction and vagina towards the pubic symphysis during the Valsalva maneuver, thereby helping to resist increases in intra-abdominal pressure. However, to reinforce this area, a fibromuscular structure called urogenital diaphragm is located behind the pelvic floor in the anterior part of the perineum.

The urogenital diaphragm is described as consisting of two muscles, the deep transverse perineal muscle and the external urethral sphincter, together with the superior and inferior fascias of the urogenital diaphragm. It forms a triangular musculofascial layer through which the urethra and, in females, the vagina pass.

Fascias

There are two fascial systems in the pelvis: the parietal pelvic fascia and the visceral pelvic fascia.

The parietal pelvic fascia covers the muscles and bony structures that form the walls of the pelvis, as well as the hypogastric vessels and sacral plexus. The fascia adheres firmly to the periosteum and underlying muscles and reflects onto the pelvic organs, helping to support and anchor them within the pelvis. Over the anterior surface of the sacrum and coccyx it is known as the presacral fascia, while over the piriformis muscle, it is referred to as the piriformis fascia.

The visceral pelvic fascia covers the surface of the pelvic organs and is not uniformly distributed, being thicker at the junctions between pelvic organs, where it forms longitudinal and transverse connective tissue bands that maintain the separation of the pelvic organs. As well as covering the surface of pelvic organs, the visceral pelvic fascia covers the ligaments of the parametrium (uterosacral ligament, cardinal ligament); it also forms the peritoneal plications, which are found in the space between pelvic organs (e.g. mesosalpinx, mesovarium, parts of the broad ligament, round ligament, utero-ovarian ligament, infundibulopelvic ligament).

The connective tissue between the parietal and visceral pelvic fascias, the so-called extra-serous pelvic fascia, contains the blood vessels and nerves supplying the pelvic organs. The pelvic fascia is not uniformly distributed and is thickened around the vagina, where it forms condensations known as the pubocervical fascia anteriorly and the rectovaginal fascia posteriorly (Figure 1).

These fascial condensations are firmly adherent to the vaginal wall and cannot be separated from it by blunt dissection. They contribute to the support of the pelvic organs and help prevent pelvic organ prolapse.

The pubocervical fascia extends from the pubis anteriorly to the ischial spine posteriorly and is attached laterally to the tendinous arch of the pelvic fascia (arcus tendineus fasciae pelvis), which overlies the levator ani muscle. 

Defects in these fascial structures are a major cause of anterior and posterior compartment prolapse.

Ligaments

Within the pelvis, ligaments provide additional support for the pelvic organs by attaching them to the pelvic sidewall.

The principal ligaments of gynecological importance are the round, uterosacral, cardinal and infundibulopelvic ligaments.

The round ligament is a dense connective tissue structure that extends from the uterine cornu to the inguinal canal. It is contained within the anterior and posterior layers of the broad ligament. Despite its name, it is not a true ligament in the anatomical sense but a fibromuscular cord, continuous with the uterine myometrium, that lies within the anterior and posterior layers of the broad ligament and is covered by peritoneum. Its principal function is to help maintain the anteverted position of the uterus, particularly in the upright position.

The uterosacral ligaments are paired structures attached ventrally to the uterine torus that extend dorsolaterally into the loose connective tissue of the retroperitoneal space, rather than inserting directly into the sacrum.⁵ Their principal role is to support the uterus in the upright position. Near their uterine origin, they lie in close proximity to the hypogastric nerve and the ureter.

The cardinal ligament has the most complex anatomy of the pelvic ligaments. It lies lateral to the uterus and upper vagina, bounded anteriorly by the pubocervical fascia and posteriorly by the rectovaginal fascia. It provides support for the cervix and upper vagina by attaching them to the pelvic sidewall along the course of the internal iliac (hypogastric) vessels, thereby helping to prevent apical prolapse.

Historically referred to as the cardinal ligament and now more commonly described as the paracervix, this connective tissue contains several structures of major importance in gynecological surgery. Medially, it forms the ureteric tunnel through which the ureter passes before entering the bladder (Figure 2).⁶

The uterine artery and superficial uterine vein are located at the superior aspect of the cardinal ligament and may be used as anatomical landmarks for its identification. Immediately inferior to the uterine artery, the ureter enters the ureteric tunnel, passing above the deep uterine vein. The deep uterine vein is an important landmark for identifying the nerve-bearing portion of the cardinal ligament.

The caudal part of the ligament, below the deep uterine vein, contains fibers of the inferior hypogastric plexus. Surgical damage to this region can cause pelvic organ dysfunction, especially impaired bladder emptying.⁷

A thorough understanding of female pelvic anatomy is essential for gynecologists and other healthcare professionals involved in the diagnosis and surgical management of disorders affecting this anatomical region

THE URETER

The ureter is one of the longest organs in the human body and probably one of the least vascularized and should be handled with care. Approximately 70% of ureteral injuries occur during gynecological procedures and most of them are recognized postoperatively.⁸ A precise knowledge of ureteral anatomy and its pathway can play a pivotal role for a gynecological surgeon transforming this structure from an enemy to an important surgical landmark.

The ureters are paired tubes that run from the kidney to the bladder, with dimensions of approximately 20–30 cm in length and 3–4 mm in diameter. The lumen of the ureter is around 2 mm, lined by urothelium and surrounded by a muscular layer, responsible for the alternating peristaltic contractions that propel urine toward the bladder (at a velocity of 2–3 cm/s). In cross section, the bundles form two muscle layers separated by connective tissue. The inner layer is mainly longitudinal whereas the outer layer is mainly circular. Near the bladder, a third longitudinal muscle layer, known as the muscle of Waldeyer, extends from the bladder wall into the intramural ureter.

The course of the ureter can be divided into abdominal and pelvic segments. In the abdominal segment, the ureter descends along the anterior surface of the psoas muscle to the pelvic brim, where it crosses the iliac arteries before entering the pelvis. From the pelvic brim onwards, the pelvic ureter can be divided into five segments:

• Parietal segment that passes over the iliac artery.
• Retroligamentous segment, which courses retroperitoneally and can be seen through the overlying peritoneum on the lateral pelvic wall.
• Intraligamentous segment where the ureter enters the ureteric tunnel, passing beneath the uterine artery and becoming obscured from the surgeon's view.
• Retrovesical segment, where the ureter joins the bladder passing between the cranial and caudal leaves of the bladder pillars.
• Vesical segment, where it passes through the bladder wall.

At the beginning of its pelvic course, the ureter runs along the lateral pelvic wall, parallel to the uterine artery and lateral to the pararectal fossa. As it approached the parametrium, it turns anteriorly to enter the ureteric tunnel beneath the uterine artery.

After entering the ureteric tunnel, the ureter courses through the medial part of the paravesical fossa. It is covered by the anterior paracervix, which separates the paravesical fossa from the vesicovaginal space (Figure 3).

Blood and nerve supply

The arterial supply of the ureter varies along its course. In the abdomen, the ureter is supplied by four or five small branches arising from the renal, gonadal, common iliac and abdominal aortic arteries. In the pelvis, the blood supply is more variable and, in women, is derived principally from branches of the uterine and vaginal arteries.

These arteries form an anastomotic network within the adventitia, so occlusion of a single vessel does not usually compromise the blood supply to the ureter. The adventitia also contains the ureteric plexus, which receives nerve fibers from the renal and aortic plexuses in the upper ureter, from the superior hypogastric plexus in the middle ureter, and from the inferior hypogastric plexus in the pelvic ureter. Sensory innervation is provided to the ureters from the T11–L2 segments of the spinal cord and ureteric pain is typically referred to the flank and groin.

NERVES AND VESSELS OF THE PELVIS

Pelvic blood supply 

The abdominal aorta, the largest artery in the human body, lies slightly to the left of the inferior vena cava. At the level of the fourth lumbar vertebra, just below the umbilicus, it bifurcates into the right and left common iliac arteries.⁹ Knowledge of this anatomy is essential for safe insertion of the primary trocar at the umbilicus, which is typically located approximately 5 cm above the aortic bifurcation. According to Sandadi et al., injury to major retroperitoneal vessels occurs in 0.3–1% of  cases during primary trocar entry.¹⁰ The inferior vena cava accompanies the abdominal aorta, lying slightly to its right. It is formed by the union of the right and left common iliac veins just above the sacral promontory. The left common iliac vein lies immediately caudal to the aortic bifurcation, just above the sacral promontory. It is an important landmark during promontory dissection for sacrocolpopexy and should be identified at the beginning of the procedure.¹¹ The middle sacral artery and vein arise from the abdominal aorta and inferior vena cava, respectively, and descend over the anterior surface of the sacrum beneath the presacral fascia. In this region, the middle sacral vessels and the superior hypogastric plexus are covered by the presacral fascia and lie in close proximity to one another. The superior hypogastric plexus divides into the right and left hypogastric nerves, which descend along the pelvic sidewall beneath the peritoneum to contribute sympathetic fibers to the inferior hypogastric plexus. (Figure 4).

The common iliac artery, approximately 5 cm in length, divides into the internal and external iliac arteries at the level of the sacroiliac joint. The external iliac artery courses along the pelvic brim without giving rise to branches supplying the pelvic viscera. Before passing beneath the inguinal ligament to become the femoral artery, it gives rise to the inferior epigastric and deep circumflex iliac arteries, which supply the anterior abdominal wall.

The external iliac vein accompanies the external iliac artery, lying slightly medial to it. Near Cooper's ligament, just before leaving the pelvis, it receives the pubic (corona mortis) vein, which anastomoses with the obturator vein, forming a venous communication between the external and internal iliac venous systems. Although this vein can usually be divided without significant consequences, it should be identified during pelvic lymphadenectomy to avoid potentially severe hemorrhage.

The internal iliac artery usually measures around 3–4 cm before it divides into a posterior and anterior trunk. The posterior trunk gives rise to the iliolumbar, lateral sacral and superior gluteal arteries, which supply the pelvic wall and gluteal region. During the surgical management of major pelvic hemorrhage, such as postpartum hemorrhage, the posterior trunk should be preserved by ligating the internal iliac (hypogastric) artery approximately 3–4 cm distal to its origin, thereby maintaining blood flow to the gluteal muscles. The anterior trunk gives rise to several branches, including the obturator, internal pudendal, inferior gluteal, uterine, superior vesical, vaginal and middle rectal arteries, which supply the pelvic muscles and pelvic organs.

The obturator artery is usually the first branch of the anterior division of the internal iliac artery and its only lateral branch. It runs along the lateral aspect of the paravesical space, accompanying the obturator vein, before leaving the pelvis through the obturator canal to supply the obturator internus muscle and adjacent structures.

The umbilical artery is usually the second branch of the anterior division of the internal iliac artery. In most individuals, the umbilical, superior vesical, and uterine arteries share a common origin. The umbilical artery is an important surgical landmark when developing the paravesical space, as it forms the medial umbilical fold, which divides the space into medial and lateral compartments.

The uterine artery courses medially in a tortuous path across the superior aspect of the paracervix to reach the lateral aspect of the uterus, accompanied by the superficial uterine vein. The common origin of the uterine and umbilical arteries is a useful landmark for identifying the uterine artery in the retroperitoneal space.

The umbilical artery can be readily identified on the anterior abdominal wall. During ventral-to-dorsal retroperitoneal dissection, the surgeon can identify the uterine artery by remaining medial to the umbilical artery.

Another important landmark is the deep uterine vein, which lies within the paracervix just below the ureter. This anatomical landmark marks the nerve-bearing portion of the paracervix.

Further inferiorly, the middle rectal artery arises from the internal iliac artery and courses medially through the pararectal space to supply the rectum. In so doing, it traverses the inferior hypogastric plexus, making it an important landmark for identifying the inferior hypogastric plexus and avoiding rectal functional damage during endometriosis surgery.¹²

The terminal branch of the internal iliac artery is the pudendal artery, which leaves the pelvis through the greater sciatic foramen inferior to the piriformis muscle after giving rise to the inferior gluteal artery.

The internal pudendal artery then passes around the sacrospinous ligament and enters the pudendal (Alcock) canal, where it is accompanied by the internal pudendal vein and pudendal nerve before continuing into the perineum.

The ovarian arteries originate arise from the abdominal aorta and course through the retroperitoneal space to the pelvic brim, where they cross above the ureter and enter the infundibulopelvic (suspensory) ligament to reach the ovary. The ovarian veins drain the ovaries and accompany the ovarian arteries, but differ in their venous drainage: the right ovarian vein drains into the inferior vena cava, whereas the left ovarian vein drains into the left renal vein.

Pelvic nerves

Pelvic innervation comprises somatic and autonomic components. The somatic nerves provide motor and sensory innervation to the pelvic floor and perineum, while the autonomic nerves regulate the function of the pelvic viscera.

The inferior hypogastric plexus is a nerve network that contains both sympathetic and parasympathetic fibers. Sympathetic fibers reach the plexus via the hypogastric nerves, which arise from the superior hypogastric plexus, and via sacral splanchnic nerves from the sympathetic trunk. The parasympathetic component is provided by the pelvic splanchnic nerves, which arise from the anterior rami of S2–S4.

The inferior hypogastric plexus lies on both the lateral and medial aspects of the pararectal space, below the level of the deep uterine vein. It divides into branches that provide autonomic innervation to the rectum, uterus and bladder.

The genitofemoral nerve (L1–L2) courses along the anterior surface of the psoas major muscle. It may be injured during pelvic lymphadenectomy or ureteric reimplantation, or by prolonged pressure from a self-retaining retractor (Figure 5). Injury may result in pain or paresthesia involving the inguinal region, labia majora and upper medial thigh. The lateral femoral cutaneous nerve (L2–L3) courses across the iliacus muscle before passing beneath the inguinal ligament. It may be compressed by retractors or excessive hip flexion, resulting in paresthesia over the anterolateral thigh.

The femoral nerve (L2–L4), the largest branch of the lumbar plexus, emerges from the lateral border of the psoas muscle and passes beneath the inguinal ligament to provide motor and sensory innervation to the anterior thigh. Injury, most commonly resulting from prolonged hip hyperflexion and excessive abduction during surgery, may cause weakness of hip flexion and knee extension.

The obturator nerve (L2–L4) arises from the lumbar plexus, descends along the lateral pelvic wall, and exits the pelvis through the obturator canal to supply the adductor muscles of the thigh and provide sensory innervation to the medial thigh. It is particularly vulnerable to injury during dissection of the obturator fossa during pelvic lymphadenectomy and may also be injured during transobturator tape (TOT) procedures. Injury results in weakness of thigh adduction and sensory loss over the medial thigh.¹³

The pudendal nerve (S2–S4) arises from the sacral plexus and accompanies the internal pudendal artery. It leaves the pelvis through the greater sciatic foramen inferior to the piriformis muscle, passes around the sacrospinous ligament, and enters the perineum through the pudendal (Alcock) canal.^{14 15} Pudendal nerve entrapment may occur during sacrospinous ligament fixation, particularly if sutures are placed too close to the ischial spine. Care should therefore be taken during this procedure.^14,15

The sciatic nerve arises from the lumbosacral plexus (L4–S3). It courses through the greater sciatic foramen, usually inferior to the piriformis muscle, to enter the gluteal region. Although uncommon, it may be injured during gynecological surgery or by prolonged lithotomy positioning with excessive hip flexion. Injury may result in hamstring weakness, sensory disturbance, loss of the Achilles tendon reflex and radiating posterior leg pain (sciatica).

In addition to the pudendal nerve, the sciatic nerve should be considered in patients with deep endometriosis involving the lateral parametrium. A thorough understanding of pelvic anatomy is essential for safe nerve-sparing dissection.

PELVIC SPACES

The pelvic spaces are potential spaces formed by the peritoneal reflections between the pelvic organs and the pelvic sidewalls. Their arrangement reflects the embryological development of the pelvic organs. During surgery, these potential spaces are developed by incising the peritoneum and separating the underlying connective tissue planes to gain access to the retroperitoneal structures. They are relatively avascular and contain loose areolar and adipose tissue.¹⁶

They represent important anatomical landmarks for safe pelvic surgery and help define the anatomical boundaries required for specific surgical procedures.¹⁷

The pelvic spaces are divided into midline and paired lateral spaces. The midline spaces develop along the midsagittal plane of the pelvis, whereas the lateral spaces lie between this plane and the pelvic sidewall. In an anteroposterior direction, the midline spaces comprise the prevesical, vesicovaginal space, rectovaginal space and retrorectal (presacral) spaces. The lateral spaces are symmetrical and include the pararectal and paravesical spaces.¹⁸

The midline spaces are more commonly approached during surgery for benign conditions, whereas the lateral spaces are more frequently dissected during oncological procedures and for the management of deep endometriosis.

Midline spaces

Prevesical (Retzius) space

The prevesical space or Retzius space is an extraperitoneal space located anteriorly in the pelvis between the umbilicovesical fascia,¹⁹ and the transversalis fascia of the abdominal wall and the pubic symphysis. It surrounds the anterior and lateral aspects of the urinary bladder. Laterally it communicates with the paravesical spaces, and inferiorly it is bounded by the pubovesical ligaments. Dissection of this space is useful for urogynecological surgery, management of bladder endometriosis, advanced stage cancers and drainage of hemorrhagic fluid collections.

The Retzius space is separated from the peritoneal cavity by the peritoneum and anteriorly by prevesical fascia.

Vesicovaginal space

The vesicovaginal space is a potential space between the vagina and the bladder and is developed during any standard hysterectomy. The space can be fully dissected leading to an avascular triangular shaped space with its apex at the caudal end of the bladder trigone and its lateral boundaries formed by the superficial vascular layer of the anterior paracervix.²⁰ Some authors consider vesicocervical and vesicouterine spaces to be continuous with the vesicovaginal space along its longitudinal axis.

Rectovaginal space

The rectovaginal space is developed by incising the peritoneal reflection of the pouch of Douglas and dissecting caudally towards the levator ani muscles. Its anterior boundary is the posterior wall of the vagina. Anteriorly, it is bounded by the posterior vaginal wall and posteriorly by the anterior wall of the rectum. Laterally it is bounded by the uterosacral ligaments and the rectal pillars. Dissection of this space is useful in the management of deep endometriosis and cervical cancer. The entrance to the rectovaginal space is located approximately 2 cm below the insertion of the uterosacral ligaments on the torus uterinus.²¹

Retrorectal space

Also known as presacral space, the retrorectal space is bounded anteriorly by the rectum, posteriorly by the sacrum and laterally by the hypogastric fascia. In a craniocaudal direction, dissection starts from the rectosigmoid peritoneal reflection to the pelvic floor.²²

There is no universal consensus regarding the fascial anatomy of this space. Two anatomical planes can be distinguished: the interfascial plane and the presacral plane. The fascia propria of the rectum (fascia propria recti) surrounds the mesorectum and rectum, whereas the presacral fascia covers the sacral promontory and the hypogastric nerves. The interfascial plane, located between the fascia propria recti and the presacral fascia, is relatively avascular and is used during rectal resection and presacral neurectomy. The presacral plane lies posterior to the presacral fascia (Waldeyer's fascia) and, in gynaecological surgery, is typically entered only at the level of the sacral promontory during sacrocolpopexy

Lateral spaces

Paravesical space

The paravesical space is bounded medially by the bladder, laterally by the pelvic sidewall, anteriorly by the pubic bone and posteriorly by the paracervix. The paracervix traverses the lateral pelvic spaces and separates the paravesical space anteriorly from the pararectal space posteriorly.

The obliterated umbilical artery divides the paravesical space into a medial and lateral compartments. The lateral compartment is dissected during oncological procedures, particularly pelvic lymphadenectomy, where the obturator internus muscle forms its lateral boundary and the obturator nerve and vessels are identified as they course towards the obturator canal. The medial paravesical space is useful during hysterectomy when dense vesicouterine adhesions are present and during ureteric reimplantation. Whereas the lateral paravesical space is relatively avascular, the medial compartment is traversed by the superior vesical vessels.²³

Pararectal space

The pararectal space is bounded medially by the rectum, laterally by the internal iliac artery, anteriorly by the paracervix and posteriorly by the pelvic sidewall. Dissection proceeds in a craniocaudal direction from the posterior leaf of the broad ligament to the pelvic floor.

The pararectal space is subdivided into medial and lateral compartments according to the position of the ureter.

The medial pararectal space, also known as Okabayashi's space, is developed medial to the ureter. It is an important landmark for nerve-sparing pelvic surgery because the ureter, uterosacral ligament and hypogastric nerve are in close proximity at this level. Development of this space facilitates identification and preservation of the hypogastric nerve. The inferior hypogastric plexus lies lateral to the medial pararectal space. The middle rectal artery, when present, may cross the plexus and is the principal vascular structure within this space. The middle rectal artery and its surrounding connective tissue have also been described as the lateral ligament of the rectum.²⁴

The lateral pararectal space, also known as Latzko’s space, is developed lateral to the ureter. Dissection of Latzko's space facilitates identification of the inferior hypogastric plexus and the sacral nerve roots. This space contains more vascular structures, allowing identification of the internal iliac artery and its anterior and posterior divisions, together with their branches.

The medial pararectal space is dissected for the management of deep endometriosis, sacrocolpopexy, ureteric and autonomic nerve identification and injury prevention, whereas the lateral pararectal space is primarily dissected during oncological procedures.²⁵

Iliolumbar space

The iliolumbar space is located between the common iliac vessels medially and the psoas muscle and pelvic sidewall laterally. It is of particular importance because it contains numerous major pelvic nerves.

Within the iliolumbar space, the lumbosacral trunk formed by contributions from the lumbar plexus, is crossed by the iliolumbar vessels before joining the sacral plexus to contribute to the sciatic nerve, which exits the pelvis through the greater sciatic foramen inferior to the piriformis muscle. The superior gluteal nerve arises from the sacral plexus and exits through the greater sciatic foramen superior to the piriformis muscle, accompanied by the superior gluteal artery and vein. The obturator nerve lies more superficially and medially, whereas the pudendal nerve lies more caudally and laterally.²⁶

The iliolumbar space is dissected primarily during surgery for pudendal neuralgia and pelvic sidewall endometriosis, and for intraoperative nerve mapping using the LANN (laparoscopic neuronavigation) technique.

Yabuki’s space

Yabuki's space, also known as the fourth space, is located between the prevesical segment of the ureter laterally and the lateral vaginal wall medially. To locate and dissect this space, the vesicovaginal plane is first developed, followed by lateral dissection towards the anterior paracervix. Dissection of this space allows identification of the prevesical segment of the ureter and lateralization and isolation of the nerve-bearing portion of the anterior paracervix.²⁷

PRACTICE RECOMMENDATIONS

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