The female inferior hypogastric (= pelvic) plexus: anatomical and radiological description of the plexus and its afferences—applications to pelvic surgery

AIM OF THE STUDY: We wanted to determine the anatomical features of the inferior hypogastric plexus (IHP), and the useful landmarks for a safe surgical approach during pelvic surgery. MATERIALS AND METHODS: We dissected the IHP in 22 formolized female anatomical subjects, none of which bore any stigmata of subumbilical surgery. RESULTS: The inferior hypogastric plexus (IHP) is a triangle with a posterior base and an anterior inferior top. It can be described as having three edges and three angles; its inferior edge stretches constantly from the fourth sacral root to the ureter's point of entry into the posterior layer of the broad ligament; its cranial edge is strictly parallel to the posterior edge of the hypogastric artery, along which it runs at a distance of 10 mm; its posterior (dorsal) edge is at the point of contact with the sacral roots, from which it receives its afferences. They most frequently originate from S3 or S4 (60%) and then, in one or two branches, often from S2 (40%), never from S1 and in exceptional cases from S5 (20%). There are sympathetic afferences in 30% of cases, usually through a single branch of the second, third or fourth sacral ganglion. All IHPs have at least one sacral afference and sometimes there may be up to three afferences from the same sacral root. Its dorsal cranial angle, which is superior, comes after the SHP (hypogastric nerve or presacral nerve filament); its anterior inferior angle is located exactly at the ureter's point of entry into the posterior layer of the broad ligament. This is the top of the IHP; its posterior inferior angle is located at the point of contact with the fourth sacral root. At its entrance at the base of the parametrium the pelvic ureter is the anterior, fundamental positional reference for the IHP. The vaginal efferences come out of the top of the IHP through branches leading to the bladder, the vagina and the rectum, which originate through two trunks exactly underneath the crossing point of the ureter and the uterine artery: (i) one trunk leading to the bladder runs along and underneath the ureter and divides into two groups, which are lateral and medial, trigonal. (ii) the trunk leading to the vagina runs along the inferior edge of the uterine artery. At the point of contact with the lateral edge of the vagina, it splits into two groups: anterior thin and posterior voluminous. Some of its branches perforate the posterior wall of the vagina and are distributed to the rectovaginal septum in a tooth comb pattern. The inferior branches, which emerge from the inferior edge of the IHP, reach the rectum directly. The dissection of the 22 specimens allowed us to describe three efferent plexuses: a vaginal rectal plexus, a vesical plexus and a inferior rectal plexus. So the IHP's anterior, fundamental positional reference is the pelvic ureter at the point where it enters at the base of the parametrium, then at the crossing point of the uterine artery. The ureter is the vector for vesical efferences, the uterine artery is the vector for vaginal efferences, which are thus sent into the vesicovaginal septum and the rectovaginal septum. This surgical point of reference is of vital importance in nerve sparing during the course of a simple or extended hysterectomy. Any dissection carried out underneath and outside of the ureter inevitably carries a risk of lesions to its efferent, lateral vesical or medial, rectovaginal fibres.     

Systematization of the vesical and uterovaginal efferences of the female inferior hypogastric plexus (pelvic): applications to pelvic surgery on women patients

Objective To locate and describe the various efferences of the plexus in order to make it easier to avoid nerve lesions during pelvic surgery on women patients through a better anatomical knowledge of the inferior hypogastric plexus (IHP). Materials and methods We dissected 27 formalin embalmed female anatomical subjects, none of which bore any stigmata of subumbilical surgery. The dissection was always performed using the same technique: identification of the inferior hypogastric plexus, whose posterior superior angle follows on from the hypogastric nerve and whose top, which is anterior and inferior, is located exactly at the ureter’s point of entry into the base of the parametrium, underneath the posterior layer of the broad ligament. Results The IHP is located at the level of the posterior floor of the pelvis, opposite to the sacral concavity. Its top, which is anterior inferior, is at the point of contact with the ureter at its entry into the posterior layer of the broad ligament. The uterovaginal, vesical and rectal efferences originate in the paracervix. Three efferent nerves branch, two of them from its top and the third from its inferior edge: (1) A vaginal nerve, medial to the ureter, follows the uterine artery and divides into two groups: anterior thin, heading for the vagina and the uterus; posterior, voluminous, heading in a superior rectal direction (=superior rectal nerve). (2) A vesical nerve, lateral to the ureter, divides into two groups, lateral and medial. (3) The inferior rectal nerve emerges from the inferior edge of the IHP, between the fourth sacral root and the ureter’s point of entry into the base of the parametrium. Conclusion The ureter is the crucial point of reference for the IHP and its efferences and acts as a real guide for identifying the anterior inferior angle or top of the IHP, the origin of the vaginal nerve, the level of the ureterovesical junction and the division of the vesical nerve into its two medial and lateral branches. Dissecting underneath and inside the ureter and the uterine artery involves a risk of lesion of the vaginal nerve and its uterovaginal branches. Further forward, between the intersection and the ureterovesical junction, dissecting and/or coagulating under the ureter involves a risk of lesions to the vesical nerve, which are likely to explain the phenomena of denervation of the anterior floor encountered after certain hysterectomies and/or surgical treatments of vesicoureteral reflux.     

Origins and distribution of nerves to the female urinary bladder: new anatomical findings in the sex differences

The development of nerve-sparing procedures is important in preventing bladder dysfunction following radical hysterectomy. In this study, we dissected 14 halves of 7 female pelvises (age range: 46-86 years; mean age: 74 years) to examine the origins, courses, and distributions of nerve branches to the bladder in females in detail, and 6 halves of 3 male pelvises (age range: 71-85 years, mean age: 78 years) to compare with the female specimens. Nerve branches to the bladder originated mainly from the inferior hypogastric plexus, but independent direct branches running along the ureter from the hypogastric nerve were also distributed particularly to the trigone in all female specimens. We classified these independent branches into four types according to their relationship to the ureter. In males the numbers of the independent branches were small and they were difficult to find. The present observations indicate that nerve distribution patterns to the bladder differ between females and males. In nerve sparing procedures for radical hysterectomy, the area between the ureter and the hypogastric nerve is important.     

Quantitative anatomical study of male pelvic autonomic plexus and its clinical potential in rectal resection

The pelvic autonomic nerves innervate the pelvic viscera, and carry a high risk of damage during surgery. This high risk has been ascribed to the complex interrelationship of pelvic paravisceral structures and the difficulty in identifying particular structures, despite the fact that the anatomic characteristics of the pelvic autonomic plexus have been well documented. We dissected ten male embalmed adult cadavers with particular attention to the quantitative parameters of the pelvic plexus and its subsidiary plexus. The right inferior hypogastric plexus and its rectal branch were found to be significantly longer and wider than the left one, while the transverse diameter of the vesical and prostatic branches of the left side was significantly larger the right. The inferior mesenteric plexus gave off fibers directly to form the pelvic plexus in four of 20 hemipelves (20%). In the side-by-side comparison, the distance to midpoint of the sacral promontory of the left rectal plexus was significantly longer than that of the right, whereas the maximum length (the length of the longest nerve fiber from origin to corresponding organ) of the left vesical plexus was significantly shorter than that of the right. Additionally, the craniocaudal and dorsoventral diameters of the right pelvic autonomic plexus were significantly shorter those of the left. The quantitative parameters relating to the pelvic autonomic plexuses not only can enhance our understanding of its anatomy and function, but can also be used as references for surgical procedures and robot-assisted surgery.     

Lateral branches of dorsal sacral nerve plexus and the long posterior sacroiliac ligament

Non-specific low back pain and peripartum pelvic pain have aetiologies that may feature the sacroiliac region. This region possesses many potential pain-generating structures sharing common sensory innervation which makes clinical differentiation of pathoanatomy difficult. This anatomical study explores the relationship between the long posterior sacroiliac ligament (LPSL) and the lateral branches of the dorsal sacral nerve plexus. Twenty-five sides of the pelvis from 16 cadavers were studied, three for histological analysis and 22 for gross anatomical dissection. We found that the LPSL is penetrated by the lateral branches of the dorsal sacral rami of predominantly S2 (96%, 21/22) and S3 (100%, 22/22), variably of S4 (59%, 13/22) and rarely of S1 (4%, 1/22). Some of the penetrating lateral branches give off nerve fibres that disappear within the ligament. These findings provide an anatomical basis for the notion that the LPSL is a potential pain generator in the posterior sacroiliac region.     

Anatomy of the pelvic plexus and innervation of the prostate gland

We have examined the anatomy of the pelvic (inferior hypogastric) plexus in six male cadavers, paying particular attention to gross anatomical landmarks that might aid in locating it and have used immunohistochemistry to study the small branches of the plexus that supply the prostate gland. The pelvic plexus was found two finger breadths lateral to the third anterior sacral foramina, lying deep to a line drawn from third sacral vertebra, the conventional level of the recto-sigmoid junction, and the palpable posterior superior surface of the pubic symphysis. Immunohistochemical staining showed small nerve branches from the pelvic plexus entering the prostate gland and the presence of ganglia within the prostate gland that contained both tyrosine hydroxylase positive and negative neuronal cell bodies. This information may be useful in nerve-sparing surgical procedures and in discussions of the functional implications of perturbations of prostate innervation.     

全直肠系膜切除相关盆自主神经的解剖学观察

目的：阐述全直肠系膜切除术相关盆自主神经的局部解剖学特点，探讨盆自主神经保留的部位和对策。方法：对20具男性盆腔固定标本进行解剖观察。结果：腹主动脉丛远离肠系膜下动脉起点；上腹下丛贴近骶岬表面；腹下神经部分毗邻输尿管；盆内脏神经伴行直肠中动脉外侧部；下腹下丛位于直肠系膜后外侧；其直肠侧支走行于直肠侧韧带内，直肠前支向前穿过Denonvilliers筋膜后叶；勃起神经位于Denonvilliers筋膜前叶外侧部。结论：盆自主神经保留的部位是：离断肠系膜下血管时的腹主动脉丛左干，直肠后分离时的上腹下丛和腹下神经，直肠侧面分离时的下腹下丛和盆内脏神经，直肠前分离时的勃起神经。共同原则是：在直肠后间隙中贴近直肠系膜操作；直视下操作；避免过度牵引直肠系膜。     

Does the cardinal ligament of the uterus contain a nerve that should be preserved in radical hysterectomy?

The cardinal ligament (CL) of the uterus is present as a specific part of the parametrium when the pararectal and paravesical spaces are developed surgically. According to usual nerve-sparing radical hysterectomy (the Tokyo method), the CL is divided into two parts, the vascular part for dissection and the nerve part that contains the pelvic splanchnic nerve (PSN) as a major target for nerve sparing. In contrast, we hypothesized that the CL and another structure outside of the usual area for surgical dissection, that is, the lateral rectal ligament, are mutually continuous and that the PSN runs through the lateral ligament rather than the CL. In the present study, a combination of routine dissection, fresh cadaver dissection and in situ sectional anatomy revealed that: (i) the CL did not contain the PSN; (ii) a well-defined fascial structure existed in the bottom or dorsal margin of the CL area; and (iii) the pelvic plexus was separated from vascular components of the CL. The present results provide a new perspective for nerve-sparing radical hysterectomy with extensive lateral parametrial dissection of the CL.     

直肠癌手术相关腹膜后自主神经的筋膜解剖学观察

目的　从临床解剖学和组织学角度进一步阐明盆自主神经的筋膜层次。 方法　选取7具尸体标本和52例接受腹腔镜直肠癌切除手术的病人,观察其自主神经与肾前筋膜-骶前筋膜的关系。切取尸体降乙结肠系膜与主髂动脉之间、直肠系膜与骶骨骨膜之间的腹膜后组织做组织学检查。 结果　解剖学观察显示,腹主动脉丛、上腹下丛、腹下神经、下腹下丛位于肾前筋膜-骶前筋膜后外侧。组织学检查显示：神经纤维位于筋膜后,部分较细的纤维位于筋膜内。 结论　自主神经位于肾前筋膜-骶前筋膜后外侧。保持这一筋膜的完整性,是直肠癌手术中保护自主神经的解剖学基础和基本方法。     

Topography of the pelvic autonomic nervous system and its potential impact on surgical intervention in the pelvis

Bladder, bowel, and sexual dysfunction caused by iatrogenic lesions of the inferior hypogastric plexus (IHP) are well known and commonly tolerated in pelvic surgery. Because the pelvic autonomic nerves are difficult to define and dissect in surgery, and their importance often ignored, we conducted a gross anatomic study of 90 adult and four fetal hemipelves. Using various non-surgical approaches, the anatomic relations and pathways of the IHP were dissected. The IHP extended from the sacrum to the genital organs at the level of the lower sacral vertebrae. It originated from three different sources: the hypogastric nerve, the sacral splanchnic nerves from the sacral sympathetic trunk (mostly the S2 ganglion), and the pelvic splanchnic nerves, which branched primarily from the third and fourth sacral ventral rami. These fibers converge to form a uniform nerve plate medial to the vascular layer and deep to the peritoneum. The posterior portion of the IHP supplied the rectum and the anterior portion of the urogenital organs; nerve fibers traveled directly from the IHP to the anterolateral wall of the rectum and to the inferolateral and posterolateral aspects of the urogenital organs. The autonomic supply from the IHP was supplemented by nerves accompanying the ureter and the arteries. An understanding of the location of the autonomic pelvic network, including important landmarks, should help prevent iatrogenic injury through the adoption of surgical techniques that reduce or prevent postoperative autonomic dysfunction.     

Extrinsic innervation of the pelvic organs in the lesser pelvis of human embryos

Realistic models to understand the developmental appearance of the pelvic nervous system in mammals are scarce. We visualized the development of the inferior hypogastric plexus and its preganglionic connections in human embryos at 4–8 weeks post-fertilization, using Amira 3D reconstruction and Cinema 4D-remodelling software. We defined the embryonic lesser pelvis as the pelvic area caudal to both umbilical arteries and containing the hindgut. Neural crest cells (NCCs) appeared dorsolateral to the median sacral artery near vertebra S1 at ~5 weeks and had extended to vertebra S5 1 day later. Once para-arterial, NCCs either formed sympathetic ganglia or continued to migrate ventrally to the pre-arterial region, where they formed large bilateral inferior hypogastric ganglionic cell clusters (IHGCs). Unlike more cranial pre-aortic plexuses, both IHGCs did not merge because the 'pelvic pouch', a temporary caudal extension of the peritoneal cavity, interposed. Although NCCs in the sacral area started to migrate later, they reached their pre-arterial position simultaneously with the NCCs in the thoracolumbar regions. Accordingly, the superior hypogastric nerve, a caudal extension of the lumbar splanchnic nerves along the superior rectal artery, contacted the IHGCs only 1 day later than the lumbar splanchnic nerves contacted the inferior mesenteric ganglion. The superior hypogastric nerve subsequently splits to become the superior hypogastric plexus. The IHGCs had two additional sources of preganglionic innervation, of which the pelvic splanchnic nerves arrived at ~6.5 weeks and the sacral splanchnic nerves only at ~8 weeks. After all preganglionic connections had formed, separate parts of the inferior hypogastric plexus formed at the bladder neck and distal hindgut.     

The innervation of the external urethral sphincter muscle

Innervation of external urethral sphincter muscle was examined in 100 human fetuses and 10 adults of both sexes. Examined nerves take place from deep perineal nerve (branch of pudendal nerve) and, probably, from pelvic splanchnic nerves (via inferior hypogastric plexus). However, this supposition needs further microscopic research. It is also concluded that pelvic splanchnic nerves and pudendal nerve arise from the same ventral branches of spinal nerves (S2-S4).     

The anatomy of the infrarenal lumbar splanchnic nerves in human cadavers: implications for retroperitoneal nerve‐sparing surgery

Injury to the nerves of the aortic‐ and superior hypogastric plexuses during retroperitoneal surgery often results in significant post‐operative complications, including retrograde ejaculation and/or loss of seminal emission in males. Although previous characterizations of these plexuses have done well to provide a basis for understanding the typical anatomy, additional research into the common variations of these plexuses could further optimize nerve‐sparing techniques for retroperitoneal surgery. To achieve this, the present study aimed to document the prevalence and positional variability of the infrarenal lumbar splanchnic nerves (LSNs) through gross dissection of 26 human cadavers. In almost all cases, two LSNs were observed joining each side of the aortic plexus, with 48% (left) and 33% (right) of specimens also exhibiting a third joining inferior to the left renal vein. As expected, the position of the LSNs varied greatly between specimens. That said, the vast majority (98%) of LSNs joining the aortic plexus were found to originate from the lumbar sympathetic trunk above the level of the inferior mesenteric artery. It was also found that, within specimens, adjacent LSNs often coursed in parallel. In addition to these nerves, 85% of specimens also demonstrated retroaortic LSN(s) that were angled more inferior compared with the other LSNs (P < 0.05), and exhibited a unique course between the aorta/common iliac arteries and the left common iliac vein before joining the superior hypogastric plexus below the aortic bifurcation. These findings may have significant implications for surgeons attempting nerve‐sparing procedures of the sympathetic nerves in the infrarenal retroperitoneum such as retroperitoneal lymphadenectomies. We anticipate that the collective findings of the current study will help improve such retroperitoneal nerve‐sparing surgical procedures, which may assist in preserving male ejaculatory function post‐operatively.     

肠系膜下动脉根部自主神经保护的解剖学基础

目的　观察肠系膜下动脉（IMA）根部与其周围自主神经的解剖学关系,为肠系膜下动脉根部自主神经保护提供解剖学证据。 方法　7例10%福尔马林固定标本进行大体解剖及显微解剖;2例新鲜标本模拟腹腔镜下直肠癌D3根治术中肠系膜下动脉根部自主神经的显露和保护。 结果　上腹下丛(SHP)的左、右侧束及束间交通支与肠系膜下动脉根部关系密切。右侧束距离肠系膜下动脉根部较远,位于肾前筋膜下。以左侧束降支为界,其近端,上腹下丛左侧束、肠系膜下丛、腹主动脉丛紧贴肠系膜下动脉根部左侧壁并相互延续,其远端左侧束走行于肾前筋膜下。左侧束降支距离IMA起点的距离不恒定。 结论　在肾前筋膜前平面分离可有效保护上腹下丛右侧束及侧束间交通支;以SHP左侧束降支作为肠系膜下动脉根部离断的解剖学标志可以有效保护左侧束。     

The nerve branches to the external anal sphincter: the macroscopic supply and microscopic structure

The study was performed using 45 pelvic half section specimens (41 fetal ones and four adults). The macroscopic dissection followed the nerve branches from their spinal roots up to the external anal sphincter. Three nerve branches were found: the anterior ramus arising from the external perineal nerve, the inferior rectal nerve and an independent posterior branch. The anterior and the inferior rectal nerve branches always emerged from the pudendal plexus. The posterior branch arising either from S4 or from the inferior rectal nerve was only found in (31%) of our cases. Five anatomical distributions are described, percentages of every type notified. The fibre content of these nerve bundle branches was evaluated through histological sections using Heidenhain's azan stain and Luxol fast blue. The branches consisted of 2,896 to 2,137 fibres, 20% of them being unmyelinated and 80% containing various myelinated fibres. The nomenclature of these nerve branches has to be debated. The terms of anterior, middle and posterior anal nerves seem more suitable.     

Variability in superior hypogastric plexus morphology and its clinical applications: a cadaveric study

BACKGROUND: The superior hypogastric plexus (SHP) that is formed anterior to the aorta and the sacral promontory and is located anterior to the L5-S1 vertebrae, normally continues as the inferior hypogastric plexus. Several variations have been described from a single trunk to a plexiform arrangement. MATERIALS AND METHODS: The SHP was dissected in 35 formalized cadavers. RESULTS: A single thin and rounded nerve was found in 17.14% of subjects. The type of a wide reticular formation was observed in 28.57% of specimens. Interestingly, a band-like nerve trunk consisting of nerve bundles connected with loose connective tissue was evident in 22.85% of cadavers. Eventually, two distinct nerves at a short distance with each other were found in 31.44% of subjects. Furthermore, we found that branches of the major and minor splanchnic nerves contributed to SHP constitution. We provided, additionally, the topographic anatomy of the SHP with regard to the sacral promontory and the abdomen midline. CONCLUSION: A detailed knowledge of the course, the morphology, the various forms and the topography of the SHP is of outmost significance for several clinical specialties.     

Anatomical study of the pudendal nerve adjacent to the sacrospinous ligament

The pudendal nerve (S3-S5) is a major branch of the sacral plexus. After branching from the sacral plexus, the pudendal nerve travels through three main regions: the gluteal region, the pudendal canal, and the perineum. In the gluteal region, the pudendal nerve lies posterior to the sacrospinous ligament. The relationship of the pudendal nerve to the sacrospinous ligament has important clinical ramifications, but there is a lack of literature examining the variations in pudendal nerve anatomy in the gluteal region. This study investigates the pudendal nerve trunking in relation to the sacrospinous ligament in 37 cadavers (73 sides of pelves) of 21 males and 16 females, ranging from 18-83 years of age. Pudendal nerve trunking could be grouped into five types: Type I is defined as one-trunked (41/73; 56.2%), Type II is two-trunked (8/73; 11%), Type III is two-trunked with one trunk as an inferior rectal nerve piercing through the sacrospinous ligament (8/73; 11%), Type IV is two-trunked with one as an inferior rectal nerve not piercing through the sacrospinous ligament (7/73; 9.5%), and Type V is three-trunked (9/73; 12.3%). In summary, 56.2% of pudendal nerves adjacent to the sacrospinous ligament were one-trunked, 31.5% were two-trunked and 12.3% were three-trunked. Fifteen inferior rectal nerves originated independently from the S4 root and never joined the main pudendal nerve. Eight of fifteen inferior rectal nerves pierced through the sacrospinous ligament, perhaps making it prone for entrapment. We measured the average diameter of the main trunk of the pudendal nerve to be 4.67 +/- 1.17 mm. We also measured the average length of the pudendal nerve trunks before terminal branching to be 25.14 +/- 10.29 mm. There was no significant statistical difference in the average length, average diameter, number of trunks, and pudendal nerve variations between male and female or right or left sides of the pelves. A detailed study of pudendal nerve trunking in relationship to the sacrospinous ligament would be useful for instruction in basic anatomy courses and in relevant clinical settings as well.