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.     

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。     

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.     

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.     

The inferior hypogastric plexus (pelvic plexus): its importance in neural preservation techniques

The progress in the surgery of male neurological cancers relies on the anatomico-surgical approach to the pelvic neural structures. The objective of our study was to provide a better understanding of the inferior hypogastric plexus (IHP) and its anatomical relationships in order to spare it during radical prostatectomy. Fifteen male formalin-preserved cadavers which had no sub-umbilical scar were used. In five subjects, the superior hypogastric plexus (SHP) and the pre-sacral plexus were displayed then the IHP and its sacral afferents (pelvic splanchnic nerves or erector nerves of Eckhardt) were dissected out. Serial sections of the IHP were then studied in ten subjects. This allowed its identification on certain imaging sections obtained in pelvic tumor pathology and these made up the "reference cuts". The IHP lies within a fibro-fatty plate which is flat, rectangular, sub-peritoneal, sagittal and symmetrical. It arises at the level of the intersection between the vas deferens and the terminal pelvic ureter and follows the postero-lateral aspect and circumvolutions of the seminal vesicle, with which there is a plane of surgical cleavage. The seminal vesicle is, therefore, an essential landmark for this neural structure. The plane of this cleavage may be used in pelvic cancer surgery. The safest technical means of respecting sexual function and the integrity of the IHP is to keep it at a distance. The preservation of a lateral layer of the seminal vesicle is probably a method of limiting these complications as long as this does not conflict with the oncological clearance. An irregular communicating branch was found in one of five cases between the IHP, the sacral plexus and the pudendal nerve. This communicating branch lay immediately behind the intersection between the vas deferens and the ureter in the sacral concavity. It overhangs the IHP in the seminal vesicle. Impotence remains a frequent complication after radical prostatectomy. The methods of neural preservation at the prostatic apex are known but neural preservation should also be carried out posteriorly at the lateral pole of the seminal vesicle. The possibility of posterior neural preservation may be assessed pre-operatively by study of the "reference sections". The cleavage plane between the seminal vesicle and the IHP may be used intra-operatively to spare the IHP. The cavernous nerve in particular emerges at the antero-inferior border of the IHP before running along the postero-lateral aspect of the prostate. It therefore passes in contact with the seminal vesicle and may as a result be injured during radical prostatectomy with vesiculectomy. A proximal communicating branch between the IHP and the pudendal nerve is irregular. Such communicating branches may explain a better recovery of sexual function in curative neurological cancer surgery. The essential relationship of the IHP is with the seminal vesicle. The two are in tight contact and the seminal vesicle has a true plane of surgical cleavage with IHP. The risk of injuries to the posterior erectile mechanisms can be reduced either by using the cleavage plane between the IHP and seminal vesicle or by leaving a layer of the seminal vesicle when the oncological conditions allow. During celio-surgery, the operator must be careful to retract the little bands of the seminal vesicle and divide the fibrous and vascular tracts which tighten during this maneuver. During an abdominal approach, dissection of the seminal vesicle takes place at the bottom of a real pit. The operator must carry out the division leaving a layer of the seminal vesicle in place rather than trying to extract all the seminal vesicle by placing the forceps blindly. This maneuver is naturally dependent on the oncological situation. The anatomical confirmation of a regular or irregular proximal or distal communicating branch between the IHP and the pudendal nerve is probably an explanation for the sometimes uncertain results of new techniques of neural preservation in curative cancer surgery.     

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.     

Smooth muscle of the male pelvic floor: An anatomic study

Knowledge of the anatomy of the male pelvic floor is important to avoid damaging the pelvic floor muscles during surgery. We set out to explore the structure and innervation of the smooth muscle (SM) of the whole pelvic floor using male fetuses. We removed en-bloc the entire pelvis of three male fetuses. The specimens were serially sectioned before being stained with Masson's trichrome and hematoxylin and eosin, and immunostained for SMs, and somatic, adrenergic, sensory and nitrergic nerve fibers. Slides were digitized for three-dimensional reconstruction. We individualized a middle compartment that contains SM cells. This compartment is in close relation with the levator ani muscle (LAM), rectum, and urethra. We describe a posterior part of the middle compartment posterior to the rectal wall and an anterior part anterior to the rectal wall. The anterior part is split into (1) a centro-levator area of SM cells localized between the right and left LAM, (2) an endo-levator area that upholsters the internal aspect of the LAM, and (3) an infra-levator area below the LAM. All these areas are innervated by autonomic nerves coming from the inferior hypogastric plexus. The core and the infra-levator area receive the cavernous nerve and nerves supplying the urethra. We thus demonstrate that these muscular structures are smooth and under autonomic influence. These findings are relevant for the pelvic surgeon, and especially the urologist, during radical prostatectomy, abdominoperineal resection and intersphincteric resection. Clin. Anat., 2019. © 2019 Wiley Periodicals, Inc.     

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.     

Innervation of the anterior perineal muscles and its morphological consideration

3 male and 3 female pelvic-halves were dissected carefully under a stereomicroscope in order to obtain more detailed data on the nerve supply to the anterior perineal muscles. At its origin from the pudendal plexus, the perineal nerve has a close relationship with the dorsal nerve of the penis or clitoris, while it tends to be separate from the inferior rectal nerve. The ischiocavernosus and the transversus perinei profundus are in general supplied by a common branch which arises from the perineal nerve at the posterior part of the ischiorectal fossa and takes a more lateral course, independent of the cutaneous branches. The bulbospongiosus and the transversus perinei superficialis receive several twigs from the medial and intermediate cutaneous branches of the perineal nerve. From the view point of nerve supply, the anterior perineal muscles may be classified into 2 groups: the lateral group comprising the ischiocavernosus and the transversus perinei profundus, the medial group comprising the bulbospongiosus and the transversus perinei superficialis.     

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.     

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。     

直肠癌患者及健康人群直肠及周围解剖结构的高分辨MRI观察

目的 应用高分辨MRI观察直肠肠壁及其周围解剖细节,为直肠癌的临床诊断和治疗提供解剖参数和依据。 方法 收集60名健康人及20例直肠癌患者的盆腔多序列参数MRI;两位高年资医师行双盲法阅片,对20例直肠癌患者行术前T分期并与术后病理对照,分析准确率;统计分析60名正常人直肠固有筋膜前、后、左、右侧的MRI显示率,以及所有研究对象的骶前筋膜、骶骨筋膜、腹膜返折、直肠侧韧带、下腹下丛的MRI显示率。结果 高分辨MRI可以清楚地显示直肠壁的黏膜层、黏膜下层和固有肌层,直肠癌术前T分期的总准确率为80%（16/20）。健康人直肠固有筋膜前、后、左、右侧的MRI显示率分别为71.7% （43/60）、96.7%（58/60）、90.0%（54/60）和83.3%（56/60）。Denonvillier′s筋膜、骶前筋膜、直肠骶骨筋膜、腹膜返折及下腹下丛的MRI显示率分别为68.8%（55/80）、65.0%（52/80）、87.8%（69/80）、86.3%（69/80）和90.0%（72/80）;直肠侧韧带的显示率较低,左侧为53.8%（43/80）,右侧为47.6%（38/80）。结论 高分辨MRI可以辨识直肠肠壁及其周围解剖细节,帮助直肠癌术前T分期及制定临床治疗方案,判断全直肠系膜切除手术的侧切缘是否浸润,提高微转移癌灶的手术切除率,减少手术并发症。     

男性盆腔内脏神经的解剖学研究及其临床意义

男性盆腔内脏神经与盆筋膜及盆内脏器的毗邻关系复杂,且个体形态学差异大,临床上涉及肛肠外科、泌尿外科、男科等多个学科,应用甚广。近年来,对内脏神经的术中保护越来越受到重视。男性盆腔内脏神经主要包括上腹下丛、腹下神经、下腹下丛(即盆丛)、盆内脏神经、膀胱丛、前列腺丛、直肠丛及其分支等。现已证明盆腔内脏神经的损伤会给患者的排便、排尿及阴茎勃起等造成功能障碍。熟悉男性盆腔内脏神经及其分支的形态特点及其与周围结构的关系,能降低手术并发症,提高患者术后生活质量。     

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.     

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。     

内踝区动脉网的显微解剖与隐神经营养血管远端蒂皮瓣的设计

目的：为隐神经营养血管远端蒂皮瓣设计提出解剖学依据。方法：30侧经动脉灌注红色乳胶成年下肢标本，解剖观测内踝区动脉来源、分支、分布及吻合。结果：内踝区动脉有9个来源，构成3条纵向的血管网：(1)内踝前动脉和踝上支的前纵向血管网；(2)骨皮穿支的中纵向血管网；(3)胫后动脉肌间隙支和踝管动脉穿支的后纵向血管网。形成3个层面的血管网：(1)骨膜血管网；(2)深筋膜血管网；(3)皮神经浅静脉血管网。内踝区骨膜、筋膜、大隐静脉、隐神经和皮肤的营养血管同源。结论：内踝区血供来源为多源性，有明显的方向性，吻合十分丰富，可以设计3种包含浅深筋膜、皮神经、浅静脉及其营养血管的小腿内侧远端蒂皮瓣：(1)以胫后动脉肌间隙支为蒂，旋转轴点在内踝最凸出点上3cm；(2)以内踝前动脉筋膜穿支为蒂；(3)以踝管区动脉穿支为蒂，旋转轴点在内踝最凸出点平面。     

Coexistence of adrenergic and cholinergic nerves in the inferior hypogastric plexus: anatomical and immunohistochemical study with 3D reconstruction in human male fetus

Classic anatomical methods have failed to determine the precise location, origin and nature of nerve fibres in the inferior hypogastric plexus (IHP). The purpose of this study was to identify the location and nature (adrenergic and/or cholinergic) of IHP nerve fibres and to provide a three-dimensional (3D) representation of pelvic nerves and their relationship to other anatomical structures. Serial transverse sections of the pelvic portion of two human male fetuses (16 and 17 weeks' gestation) were studied histologically and immunohistochemically, digitized and reconstructed three-dimensionally. 3D reconstruction allowed a 'computer-assisted dissection', identifying the precise location and distribution of the pelvic nerve elements. Proximal (supra-levator) and distal (infra-levator) communications between the pudendal nerve and IHP were observed. By determining the nature of the nerve fibres using immunostaining, we were able to demonstrate that the hypogastric nerves and pelvic splanchnic nerves, which are classically considered purely sympathetic and parasympathetic, respectively, contain both adrenergic and cholinergic nerve fibres. The pelvic autonomic nervous system is more complex than previously thought, as adrenergic and cholinergic fibres were found to co-exist in both 'sympathetic' and 'parasympathetic' nerves. This study is the first step to a 3D cartography of neurotransmitter distribution which could help in the selection of molecules to be used in the treatment of incontinence, erectile dysfunction and ejaculatory disorders.     

An anatomical investigation on the muscles of the pelvic outlet in crab-eating monkey (Macaca irus) and Japanese monkey (Macaca fuscata) with special reference to their nerve supply

For a fuller understanding of the nerve supply to the muscles of the pelvic outlet in man, 4 pelvic-halves of crab-eating monkeys and 6 pelvic-halves of Japanese monkeys were minutely dissected. 1) The composition of the pudendal plexus tends to be limited to 2 segments, S1 and S2. 2) If we consider the origin of the nerves, the pudendal plexus is divided into 2, the first or medial and the second or lateral parts. From the first part arise the pelvic splanchnic nerves, the nerve to the iliopubocaudalis and the nerve to the ischiocaudalis. From the second part the dorsal nerve of the penis or clitoris, the perineal nerve and the inferior rectal nerve originate. 3) A laminate arrangement exists among the 3 nerves from the first part at their origin; the pelvic splanchnic nerves are situated ventrally, and the nerve to the ischiocaudalis dorsally, with the nerve to the iliopubocaudalis in between. No obvious laminate arrangement exists among the 3 nerves from the second part. 4) The part of the iliopubocaudalis, contiguous with the rectal wall but without attaching to it, has no branches of supply from the perineal nerve and the inferior rectal nerve. 5) A detailed discussion of our findings in relation to man, is given below.