Review: Pelvic nerves - from anatomy and physiology to clinical applications

Emergency treatment of pelvic ring injuries: state of the art

High energy pelvic injuries sustain significant mortality rates, due to acute exsanguination and severe associated injuries. Managing the hemodynamically unstable trauma patient with a bleeding pelvic fracture still forms a major challenge in acute trauma care. Various approaches have been applied through the last decades. At present the concept of Damage Control Resuscitation (DCR) is universally accepted and applied in major trauma centers internationally. DCR combines hemostatic blood transfusions to restore blood volume and physiologic stability, reduced crystalloid fluid administration, permissive hypotension, and immediate hemorrhage control by operative or angiographic means. Different detailed algorithms and orders of hemostatic procedures exist, without clear consensus or guidelines, depending on local traditions and institutional setups. Fracture reduction and immediate stabilization with a binder constitute the basis for angiography and embolization (AE) or pelvic packing (PP) in the hemodynamically unstable patient. AE is time consuming and may not be available 24/7, whereas PP offers a quick and technically easy procedure well suited for the patient in extremis. Resuscitative endovascular balloon occlusion of the aorta (REBOA) has also been described as a valuable adjunct in hemostatic non-responders, but merely constitute a bridge to surgical or angiographic hemostasis and its definitive role in DCR is not yet clearly established. A swift algorithmic approach to the hemodynamically unstable pelvic injury patient is required to achieve optimum results. The present paper summarizes the available literature on the acute management of the bleeding pelvic trauma patient, with emphasis on initial assessment and damage control resuscitation including surgical and angiographic hemostatic procedures. Furthermore, initial treatment of open fractures and associated injuries to the nervous and genitourinary system is outlined.

Entrapped by pain: The diagnosis and management of endometriosis affecting somatic nerves

Somatic nerve entrapment caused by endometriosis is an underrecognized and often misdiagnosed issue that leads to many women suffering unnecessarily. While the classic symptoms of endometriosis are well-known to the gynaecologic surgeon, the dermatomal-type pain caused by endometriosis impacting neural structures is not within gynecologic day-to-day practice, which often complicates diagnosis and delays treatment. A thorough understanding of pelvic neuroanatomy and a neuropelveologic approach is required for accurate assessments of patients with endometriosis and nerve entrapment. Magnetic resonance imaging is the preferred imaging modality for this presentation of endometriosis. Surgical management with laparoscopic or robotic-assisted techniques is the preferred approach to treatment, with excellent long-term results reported after nerve detrapment and endometriosis excision. The review calls for increased awareness and education on the links between endometriosis and the nervous system, advocating for patient-centered care and further research to refine the diagnosis and treatment of this challenging condition.

3D MR neurography with gadolinium contrast to improve the visualization of pelvic nerves and the branches

Objective

To evaluate the effectiveness of 3D NerveVIEW sequence with gadolinium contrast on the visualization of pelvic nerves and their branches compared to that without contrast.

Methods

Participants were scanned twice using 3D NerveVIEW sequence with and without gadolinium contrast to acquire pelvic nerve images. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and contrast ratio of the nerves were calculated and compared to determine the quality of images. To subjectively assess, using a 3-point scale, branch nerves critical to therapeutic decision-making, including the pelvic splanchnic nerve and pelvic plexus, the superior gluteal nerve, and the pudendal nerve.

Results

In the 32 eligible participants after using contrast, the CNRs of the images of nerve-to-bone and nerve-to-vessel significantly increased (p < 0.05). The CR of the images with contrast of all nerve-to-surrounding tissues (i.e., bone, muscle, blood vessels, and fat) were also found significantly higher (p < 0.05). The assessment of observers also shows higher scores for images with contrast compared to images without contrast.

Conclusion

The 3D NerveVIEW sequence combined with gadolinium contrast improved vascular suppression, increased the contrast between pelvic nerves and surrounding tissue, and enhanced the visualization of nerves and their branches. This study may be helpful for the technically challenging preoperative planning of pelvic diseases surgery.

Key Anatomical Concepts, Landmarks, and Proposed Terminology for Nerve-Sparing Gynecologic Surgery: A Narrative Review

OBJECTIVE

To synthesize the terminology utilized in nerve-sparing surgical literature and propose standardized and nonconflicting terms to allow for consistent vocabulary.

DESIGN

We performed a literature search on PubMed using the search terms "pelvis" and "nerve-sparing." Nongynecologic surgery and animal studies were excluded. A narrative review was performed, focusing on nerves, fasciae, ligaments, and retroperitoneal spaces. Terms from included papers were discussed by all authors, who are surgeons versed in nerve-sparing procedures and one anatomist, and recommendations were made regarding the most appropriate terms based on the frequency of occurrence in the literature and the possibility of overlapping names with other structures.

RESULTS

224 articles were identified, with 81 included in the full-text review. Overall, 48% of articles focused on cervical cancer and 26% on deeply infiltrating endometriosis. Findings were synthesized both narratively and visually. Inconsistencies in pelvic anatomical nomenclature were prevalent across publications. The structure with the most varied terminology was the rectal branch of the inferior hypogastric plexus with 14 names. A standardized terminology for pelvic autonomic nerve structures, fasciae, ligaments, and retroperitoneal spaces was proposed to avoid conflicting terms.

CONCLUSION

Surgeons and anatomists should use consistent terminology to facilitate increased uptake of nerve-sparing techniques in gynecologic surgery through a better understanding of surgical technique description. We have proposed a standardized terminology believed to facilitate this goal.

Anatomical Location of the Vesical Branches of the Inferior Hypogastric Plexus in Human Cadavers

We have demonstrated in canines that somatic nerve transfer to vesical branches of the inferior hypogastric plexus (IHP) can be used for bladder reinnervation after spinal root injury. Yet, the complex anatomy of the IHP hinders the clinical application of this repair strategy. Here, using human cadavers, we clarify the spatial relationships of the vesical branches of the IHP and nearby pelvic ganglia, with the ureteral orifice of the bladder. Forty-four pelvic regions were examined in 30 human cadavers. Gross post-mortem and intra-operative approaches (open anterior abdominal, manual laparoscopic, and robot-assisted) were used. Nerve branch distances and diameters were measured after thorough visual inspection and gentle dissection, so as to not distort tissue. The IHP had between 1 to 4 vesical branches (2.33 ± 0.72, mean ± SD) with average diameters of 0.51 ± 0.06 mm. Vesical branches from the IHP arose from a grossly visible pelvic ganglion in 93% of cases (confirmed histologically). The pelvic ganglion was typically located 7.11 ± 6.11 mm posterolateral to the ureteral orifice in 69% of specimens. With this in-depth characterization, vesical branches from the IHP can be safely located both posterolateral to the ureteral orifice and emanating from a more proximal ganglionic enlargement during surgical procedures.

Sex Differences in Sexual Motivation in Humans and Other Mammals: The Role of Conscious and Unconscious Processes

In self-report questionnaires, men report higher scores than women on variables such as desire for sex, frequency of sexual thoughts, number of sex partners, etc. Based on this, men are considered to have a higher level of sexual motivation than women. However, retrospective self-reports may be unsuitable for estimations of the inherent level of sexual motivation. We review data on automatic (unconsciously controlled) responses and measures of implicit motivation during exposure to sexual stimuli. These responses and measures are inaccessible to willful manipulations and make it possible to determine whether the sex difference in answers to questionnaires is replicated when volitional response manipulations are unlikely. We complement the human data with observations from some rodent and non-human primate species. The attentional resources allotted to stimuli with sexual relevance as well as genital responses to such stimuli are similar in men and women. Measures of implicit motivation also fail to detect any sex difference. Finally, the frequency of masturbation is superior in female infants before the age at which social expectations begin to determine behavior. Neither in rodents nor in non-human primates is there any clear-cut evidence for sex differences in motivation. It seems that males and females are similar with regard to the intensity of sexual motivation. The responses to questionnaires may be affected by social learning of sexual scripts and/or the inferior quality of sexual experiences in women, among other things.

Automatic muscle impedance and nerve analyzer (AMINA) as a novel approach for classifying bioimpedance signals in intraoperative pelvic neuromonitoring

Frequent complications arising from low anterior resections include urinary and fecal incontinence, as well as sexual disorders, which are commonly associated with damage to the pelvic autonomic nerves during surgery. To assist the surgeon in preserving pelvic autonomic nerves, a novel approach for intraoperative pelvic neuromonitoring was investigated that is based on impedance measurements of the innervated organs. The objective of this work was to develop an algorithm called AMINA to classify the bioimpedance signals, with the goal of facilitating signal interpretation for the surgeon. Thirty patients included in a clinical investigation underwent nerve-preserving robotic rectal surgery using intraoperative pelvic neuromonitoring. Contraction of the urinary bladder and/or rectum, triggered by direct stimulation of the innervating nerves, resulted in a change in tissue impedance signal, allowing the nerves to be identified and preserved. Impedance signal characteristics in the time domain and the time-frequency domain were calculated and classified to develop the AMINA. Stimulation-induced positive impedance changes were statistically significantly different from negative stimulation responses by the percent amplitude of impedance change Amax in the time domain. Positive impedance changes and artifacts were distinguished by classifying wavelet scales resulting from peak detection in the continuous wavelet transform scalogram, which allowed implementation of a decision tree underlying the AMINA. The sensitivity of the software-based signal evaluation by the AMINA was 96.3%, whereas its specificity was 91.2%. This approach streamlines and automates the interpretation of impedance signals during intraoperative pelvic neuromonitoring.

Surgical Anatomy and Dissection of the Hypogastric Plexus in Nerve-Sparing Radical Hysterectomy

Radical hysterectomy is a central surgical procedure in gynecological oncology. A nerve-sparing approach is essential to minimize complications from iatrogenic injury to the pelvic nerves, resulting in postoperative urinary, anorectal, and sexual dysfunction. The hypogastric plexus (HP), a complex network of sympathetic and parasympathetic nerves, plays a critical role in pelvic autonomic innervation. This article offers a comprehensive overview of the surgical anatomy of the HP and provides a step-by-step description of HP dissection, with a particular emphasis on preserving the bladder nerve branches of the inferior HP. A thorough understanding and mastery of the anatomical and surgical nuances of HP dissection are crucial for optimizing outcomes in nerve-sparing gynecologic-oncological procedures.

Peripheral Nerve Blocks for Cesarean Delivery Analgesia: A Narrative Review

Effective postoperative analgesia using multimodal approach improves maternal and neonatal outcomes after cesarean delivery. The use of neuraxial approach (local anesthetic and opioids) and intravenous adjunctive drugs, such as nonsteroidal anti-inflammatory drugs and acetaminophen, currently represents the standard regimen for post-cesarean delivery analgesia. Peripheral nerve blocks may be considered in patients who are unable to receive neuraxial techniques; these blocks may also be used as a rescue technique in selected patients. This review discusses the relevant anatomy, current evidence, and advantages and disadvantages of the various peripheral nerve block techniques. Further research is warranted to compare the analgesic efficacy of these techniques, especially newer blocks (e.g., quadratus lumborum blocks and erector spinae plane blocks). Moreover, future studies should determine the safety profile of these blocks (e.g., fascial plane blocks) in the obstetric population because of its increased susceptibility to local anesthetic toxicity.

Technical aspects of a new approach to intraoperative pelvic neuromonitoring during robotic rectal surgery

It has been found that rectal surgery still leads to high rates of postoperative urinary, fecal, or sexual dysfunction, which is why nerve-sparing surgery has gained increasing importance. To improve functional outcomes, techniques to preserve pelvic autonomic nerves by identifying anatomic landmarks and implementing intraoperative neuromonitoring methods have been investigated. The objective of this study was to transfer a new approach to intraoperative pelvic neuromonitoring based on bioimpedance measurement to a clinical setting. Thirty patients (16 male, 14 female) involved in a prospective clinical investigation (German Clinical Trials Register DRKS00017437, date of first registration 31/03/2020) underwent nerve-sparing rectal surgery using a new approach to intraoperative pelvic neuromonitoring based on direct nerve stimulation and impedance measurement on target organs. Clinical feasibility of the method was outlined in 93.3% of the cases. Smooth muscle contraction of the urinary bladder and/ or the rectum in response to direct stimulation of innervating functional nerves correlated with a change in tissue impedance compared with the pre-contraction state. The mean amplitude (Amax) of positive signal responses was Amax = 3.8%, negative signal responses from a control tissue portion with no stimulation-induced impedance change had an amplitude variation of 0.4% on average. The amplitudes of positive and negative signal responses differed significantly (statistical analysis using two-sided t-test), allowing the nerves to be identified and preserved. The results indicate a reliable identification of pelvic autonomic nerves during rectal surgery.

Dichotomous colorectal cancer behaviour

Colorectal cancer (CRC) is the third most common malignant tumor and one of the deadliest cancers. At molecular level, CRC is a heterogeneous disease that could be divided in four Consensus Molecular Subtypes. Given the differences in the disease due to its anatomical location (proximal and distal colon), another classification should be considered. Here, we review the current knowledge on CRC dichotomic´s behaviour based on two different entities; right and left-sided tumors, their impact on clinical trial data, microbiota spatial composition and the interaction with the nervous system. We discuss recent advances in understanding how the spatial tumor heterogeneity influences the tumor growth, progression, and responses to current therapies.

Nerve-Sparing Gynecologic Surgery Enabled by A Near-Infrared Nerve-Specific Fluorophore Using Existing Clinical Fluorescence Imaging Systems

Patients undergoing gynecological procedures suffer from lasting side effects due to intraoperative nerve damage. Small, delicate nerves with complex and nonuniform branching patterns in the female pelvic neuroanatomy make nerve-sparing efforts during standard gynecological procedures such as hysterectomy, cystectomy, and colorectal cancer resection difficult, and thus many patients are left with incontinence and sexual dysfunction. Herein, a near-infrared (NIR) fluorescent nerve-specific contrast agent, LGW08-35, that is spectrally compatible with clinical fluorescence guided surgery (FGS) systems is formulated and characterized for rapid implementation for nerve-sparing gynecologic surgeries. The toxicology, pharmacokinetics (PK), and pharmacodynamics (PD) of micelle formulated LGW08-35 are examined, enabling the determination of the optimal imaging doses and time points, blood and tissue uptake parameters, and maximum tolerated dose (MTD). Application of the formulated fluorophore to imaging of female rat and swine pelvic neuroanatomy validates the continued clinical translation and use for real-time identification of important nerves such as the femoral, sciatic, lumbar, iliac, and hypogastric nerves. Further development of LGW08-35 for clinical use will unlock a valuable tool for surgeons in direct visualization of important nerves and contribute to the ongoing characterization of the female pelvic neuroanatomy to eliminate the debilitating side effects of nerve damage during gynecological procedures.

Challenges in the Diagnosis and Individualized Treatment of Cervical Cancer

Cervical cancer is still the fourth most common cancer in women throughout the world; an estimated 604,000 new cases were observed in 2020. Better knowledge of its pathogenesis, gained in recent years, has introduced new preventive and diagnostic approaches. Knowledge of its pathogenesis has made it possible to provide individualized surgical and drug treatment. In industrialized countries, cervical cancer has become a less frequent tumor entity due to the accessibility of the human papilloma virus vaccination, systematic preventive programs/early detection programs, health care infrastructure and the availability of effective therapy options. Nevertheless, globally, neither mortality nor morbidity has been significantly reduced over the past 10 years, and therapy approaches differ widely. The aim of this review is to address recent advances in the prevention, diagnostic investigation and treatment of cervical cancer globally, focusing on advances in Germany, with a view toward providing an updated overview for clinicians. The following aspects are addressed in detail: (a) the prevalence and causes of cervical cancer, (b) diagnostic tools using imaging techniques, cytology and pathology, (c) pathomechanisms and clinical symptoms of cervical cancer and (d) different treatment approaches (pharmacological, surgical and others) and their impact on outcomes.

The neural pathway of the hyperthermic response to antagonists of the transient receptor potential vanilloid-1 channel

We identified the neural pathway of the hyperthermic response to TRPV1 antagonists. We showed that hyperthermia induced by i.v. AMG0347, AMG 517, or AMG8163 did not occur in rats with abdominal sensory nerves desensitized by pretreatment with a low i.p. dose of resiniferatoxin (RTX, TRPV1 agonist). However, neither bilateral vagotomy nor bilateral transection of the greater splanchnic nerve attenuated AMG0347-induced hyperthermia. Yet, this hyperthermia was attenuated by bilateral high cervical transection of the spinal dorsolateral funiculus (DLF). To explain the extra-splanchnic, spinal mediation of TRPV1 antagonist-induced hyperthermia, we proposed that abdominal signals that drive this hyperthermia originate in skeletal muscles - not viscera. If so, in order to prevent TRPV1 antagonist-induced hyperthermia, the desensitization caused by i.p. RTX should spread into the abdominal-wall muscles. Indeed, we found that the local hypoperfusion response to capsaicin (TRPV1 agonist) in the abdominal-wall muscles was absent in i.p. RTX-desensitized rats. We then showed that the most upstream (lateral parabrachial, LPB) and the most downstream (rostral raphe pallidus) nuclei of the intrabrain pathway that controls autonomic cold defenses are also required for the hyperthermic response to i.v. AMG0347. Injection of muscimol (inhibitor of neuronal activity) into the LPB or injection of glycine (inhibitory neurotransmitter) into the raphe blocked the hyperthermic response to i.v. AMG0347, whereas i.v. AMG0347 increased the number of c-Fos cells in the raphe. We conclude that the neural pathway of TRPV1 antagonist-induced hyperthermia involves TRPV1-expressing sensory nerves in trunk muscles, the DLF, and the same LPB-raphe pathway that controls autonomic cold defenses.

Risk factors for postoperative urinary retention in patients undergoing colorectal surgery: a systematic review and meta-analysis

PURPOSE

Postoperative urinary retention (POUR) is a common complication following colorectal surgery. The incidence of POUR among colorectal surgery patients varies widely, and the risk factors and outcomes of POUR are also debatable. This meta-analysis aims to systematically evaluate the risk factors for POUR in patients after colorectal surgery.

METHODS

PubMed, Web of Science, the Cochrane Library, Embase, Medline, and Chinese databases (CBM, CNKI, and WanFang Databases) were searched to identify relevant cohort studies (from inception to August 2022). Two researchers independently conducted literature quality evaluation and data extraction. All data were analyzed by using the Review Manager 5.4 software.

RESULTS

Nineteen studies with 101,025 patients were included in this meta-analysis. The risk factors for POUR in colorectal surgery patients were male sex, older age, diabetes mellitus, urological diseases, tumor location in the lower rectum, APR, laparoscopic surgery, operation time ≥ 4 h, postoperative date of urinary catheter removal, excessive intraoperative intravenous fluid volume, and postoperative ileus. The postoperative anastomotic leak, on the other hand, was not a risk factor for POUR.

CONCLUSIONS

Multiple risk factors influence the incidence of POUR in patients undergoing colorectal surgery. To reduce the incidence of POUR in colorectal surgery patients, medical staff should identify risk factors early and enforce interventions to prevent them.

The Pelvic and Sacral Splanchnic Nerves - Identification by Dissection, Trajectory

The modern principles in pelvic surgery imply the preservation of the nervous structures that are involved in the physiological functioning of the pelvic and genital organs. The main pelvic nervous element is represented by the inferior hypogastric plexus. This plexus receives sympathetic afferent fibres from the hypogastric nerve, parasympathetic afferent fibres from the pelvic splanchnic nerves and also sympathetic afferent fibres coming from the sympathetic sacral chain via the sacral splanchnic nerves. We aimed to demonstrate the anatomy of these structures through dissection and we exposed the origins, pathway and manner of distribution of the splanchnic nerves of the pelvis. We managed to clarify the main anatomical relations of these nerves, among which we highlighted the relation to the branches of the internal iliac artery. The parasympathetic fibres reach the pelvis by running through the anterior rami of the spinal nerves, which are the origin of the sacral plexus. We managed to exhibit the way in which the parasympathetic fibres emerge from the sacral nerves and form the pelvic splanchnic nerves. Pelvic surgery nowadays is focused on nerve-sparing, which essentially means the conservation of the integrity of splanchnic nerves, hypogastric nerves and inferior hypogastric plexuses in order to maintain the normal functioning of the anatomical sphincters and genital organs. In this respect, it is crucial for the surgeon who performs pelvic procedures to be more than well-acquainted to the anatomy of the pelvic splanchnic nerves, which are considered to be the erectile nerves, and to that of the sacral splanchnic nerves.

Assessment of the Versius Robotic Surgical System in Minimal Access Surgery: A Systematic Review

Background: Despite the superiority of minimal access surgery (MAS) over open surgery, MAS is difficult to perform and has a demanding learning curve. Robot-assisted surgery is an advanced form of MAS. The Versius® surgical robot system was developed with the aim of overcoming some of the challenges associated with existing surgical robots. The present study was designed to investigate the feasibility, clinical safety, and effectiveness of the Versius system in MAS. Materials and Methods: A comprehensive search was carried out in the Medline, Web of Science Core Collection (Indexes = SCI-EXPANDED, SSCI, A & HCI Timespan), and Scopus databases for articles published until February 2022. The keywords used were Versius robot, visceral, colorectal, gynecology, and urologic surgeries. Articles on the use of the Versius robot in minimal access surgery (MAS) were included in the review. Results: Seventeen articles were reviewed for the study. The investigation comprised a total of 328 patients who had been operated on with this robot system, of which 48.3%, 14.2%, and 37.5% underwent colorectal, visceral, and gynecological procedures, respectively. Postoperative and major complications within 30 days varied from 7.4% to 39%. No major complications and no readmissions or reoperations were reported in visceral and gynecological surgeries. Readmission and reoperation rates in colorectal surgeries were 0–9%. Some procedures required conversion to conventional laparoscopic surgery (CLS) or open surgery, and all procedures were completed successfully. Based on the studies reviewed in the present report, we conclude that the Versius robot can be used safely and effectively in MAS. Conclusions: A review of the published literature revealed that the Versius system is safe and effective in minimal access surgery. However, the data should be viewed with caution until randomized controlled trials (RCTs) have been performed. Studies on the use of this robotic system in oncological surgery must include survival as one of the addressed outcomes.

The distribution of the inferior hypogastric plexus in female pelvis

Elements that comprise the inferior hypogastric plexus are difficult to expose, intricate, and highly variable and can easily be damaged during local surgical procedures. We aimed to highlight, through dissection, the origin, formation, and distribution of the hypogastric nervous structures and follow them in the female pelvis. We performed detailed dissections on 7 female formalin-fixed cadavers, focusing on structures surrounding the pelvic organs. For each hemipelvis, we removed the peritoneum from the pelvic floor, and after we identified the hypogastric nerves, we continued our dissection towards the inferior hypogastric plexuses, following the branches of the latter. Laterorectally, the hypogastric nerves form the inferior hypogastric plexus, a variable structure - nervous lamina, neuronal network (more frequently), or sometimes a combination of them. We identified three components of the inferior hypogastric plexus. The anterior bundle travels towards the base of the urinary bladder, the middle part innervates the uterus and the vagina, and the posterior segment provides the innervation of the rectum. The plexus can be identified after removing the pelvic peritoneum and the subperitoneal adipose tissue. Intraoperatively, the structures can be preserved by using an immediately-subperitoneal dissection plane. The variable branches are relatively well-organized around the pelvic vessels, supplying the urinary bladder, the genital organs, and the rectum. The ureter is surrounded by some branches, especially in its last segment, and it also receives innervation directly from the hypogastric nerve. Close to the viscera, the nerves enter neurovascular plexuses, making the intraoperative separation of the nerves and the vessels virtually impossible.