Topographic anatomy of the male perineal structures with special reference to perineal approaches for radical prostatectomy

Role of puboperinealis and rectourethralis muscles as a urethral support system to maintain urinary continence after robot-assisted radical prostatectomy

The present study investigated the role of a urethral support system to maintain urinary continence after robot-assisted radical prostatectomy (RARP), with a focus on pelvic floor muscles, such as the puboperinealis muscle (PPM) and rectourethralis muscle (RUM). Finally, 323 patients who underwent RARP were analyzed in this study. All patients performed a one-hour pad test 1, 3, 6, 9, and 12 months after RARP to assess urinary incontinence and MRI before and 9 months after RARP to evaluate the pelvic anatomical structure. The preoperative cross-sectional area of PPM (2.21 ± 0.69 cm2) was significantly reduced by 19% after RARP (1.79 ± 0.60 cm2; p < 0.01). Positive correlations were observed between the amount of urinary leakage according to the 1-h pad test 1, 3, 6, 9, and 12 months after RARP and the change in the cross-sectional area of PPM by RARP (p < 0.01, < 0.001, < 0.001, < 0.001, and < 0.001, respectively). A positive correlation was also noted between the amount of urinary leakage 6 and 12 months after RARP and the preoperative RUM diameter (p < 0.05). The amount of urinary leakage 1, 3, 6, 9, and 12 months after RARP negatively correlated with the change in the antero-posterior diameter of the membranous urethra (MU diameter) from the static to dynamic phases during the Valsalva maneuver by cine MRI. Furthermore, the change in the MU diameter negatively correlated with the change in the cross-sectional area of PPM (p < 0.05). PPM and RUM play significant roles as a supportive mechanism to maintain urinary continence by functioning as a urethral support.

Pelvic floor and perineal muscles: a dynamic coordination between skeletal and smooth muscles on pelvic floor stabilization

The purpose of this review is to present our researches on the pelvic outlet muscles, including the pelvic floor and perineal muscles, which are responsible for urinary function, defecation, sexual function, and core stability, and to discuss the insights into the mechanism of pelvic floor stabilization based on the findings. Our studies are conducted using a combination of macroscopic examination, immunohistological analysis, 3D reconstruction, and imaging. Unlike most previous reports, this article describes not only on skeletal muscle but also on smooth muscle structures in the pelvic floor and perineum to encourage new understanding. The skeletal muscles of the pelvic outlet are continuous, which means that they share muscle bundles. They form three muscle slings that pass anterior and posterior to the anal canal, thus serving as the foundation of pelvic floor support. The smooth muscle of the pelvic outlet, in addition to forming the walls of the viscera, also extends in three dimensions. This continuous smooth muscle occupies the central region of the pelvic floor and perineum, thus revising the conventional understanding of the perineal body. At the interface between the levator ani and pelvic viscera, smooth muscle forms characteristic structures that transfer the lifting power of the levator ani to the pelvic viscera. The findings suggest new concepts of pelvic floor stabilization mechanisms, such as dynamic coordination between skeletal and smooth muscles. These two types of muscles possibly coordinate the direction and force of muscle contraction with each other.

Various significant connections of the male pelvic floor muscles with special reference to the anal and urethral sphincter muscles

The male pelvic floor is a complex structure formed by several muscles. The levator ani muscle and the perineal muscles are important components of the pelvic floor. The perineal muscles comprise the external anal sphincter, bulbospongiosus, superficial transverse perineal muscles, and ischiocavernosus. Although the connections of the muscles of the pelvic floor have been reported recently, the anatomical details of each muscle remain unclear. In this study, we examined the male pelvic floor to clarify the connection between the muscles related to function. Fifteen male pelvises were used for microscopic dissection, and three male pelvises were used for histological examination. On the lateral aspect, the perineal muscles were connected to each other. Bundles of the levator ani muscle extended to connect to the perineal muscles. In addition, the extended muscle bundle from the levator ani muscle and the perineal muscles surround the external urethral sphincter. On the medial aspect, the levator ani muscle and the external anal sphincter form the anterior and posterior muscular slings of the anal canal. The connection between the perineal muscles and levator ani muscle indicates a possible close relationship between the functions of the urethra and anus.

The evolution and resurgence of perineal prostatectomy in the robotic surgical era

PURPOSE

To review the recent advances in terms of surgical technique and new robotic platforms applied to radical perineal prostatectomy (RPP).

METHODS

A literature review was performed focusing on original articles on perineal prostatectomy searching via Medline/Pubmed and Embase. The entire spectrum was covered such as development of surgical technique including pelvic lymphadenectomy, adoption of novel surgical platforms, learning curve and future directions.

RESULTS

Surgical removal of the prostate plays a significant role on the treatment of localized prostate cancer (PCa). RPP was the first surgical approach described for radical prostatectomy. This technique declined in popularity secondary to the development of the retropubic approach. Recently, the appearance of novel robotic technology has generated renewed interest in the perineal approach.

CONCLUSION

There has been a recent resurgence on the interest of radical perineal prostatectomy for the treatment of localized PCa driven by the advent of new robotic surgical technologies into the field. Future studies are needed to better determine the learning curve of the perineal approach and its current role in the treatment of prostate cancer.

Precise Three-Dimensional Morphology of the Male Anterior Anorectum Reconstructed From Large Serial Histologic Sections: A Cadaveric Study

BACKGROUND

Deep anatomic knowledge of the male anterior anorectum is important to avoid urethral injury and rectal perforation in intersphincteric resection or abdominoperineal resection for very low rectal cancer. However, its structure is difficult to understand, because the anorectum, muscles, and urogenital organs are complicatedly and 3-dimensionally arranged.

OBJECTIVE

The purpose of this study was to revisit the anatomic information of the male anterior anorectum for intersphincteric resection and abdominoperineal resection with a focus on the spatial muscular morphology.

DESIGN

This was a descriptive cadaveric study.

SETTINGS

The study was conducted at Ehime and Kyoto universities.

PATIENTS

Tissue specimens from 9 male cadavers were included.

MAIN OUTCOME MEASURES

Specimens around the anterior anorectum were serially sectioned in the horizontal, sagittal, or frontal plane; large semiserial histologic sections were created at 250-μm intervals. The series were stained with Elastica van Gieson, and some sections from the series were studied by immunohistochemistry to detect smooth and striated muscles. Two series were digitalized and reconstructed 3-dimensionally.

RESULTS

Two regions without a clear anatomic border were elucidated: 1) the anterior region of the external anal sphincter, where the external anal sphincter, bulbospongiosus muscle, and superficial transverse perineal muscle were intertwined; and 2) the rectourethralis muscle, where the smooth muscle of the longitudinal muscle continuously extended to the posteroinferior area of the urethra, which became closest to the anorectum at the prostatic apex level. A tight connection between the striated and smooth muscles was identified at the anterior part of the upper external anal sphincter and anterolateral part of the puborectalis muscle level.

LIMITATIONS

This study involved a small sample size of elderly cadavers.

CONCLUSIONS

This study clarified the precise spatial relationship between smooth and striated muscles. The detailed anatomic findings will contribute more accurate step-by-step anterior dissection in intersphincteric resection and abdominoperineal resection, especially with the transanal approach, which can magnify the muscle fiber direction and contraction of striated muscle by electrostimulation. MORFOLOGÍA TRIDIMENSIONAL PRECISA DEL ANORRECTO ANTERIOR MASCULINO RECONSTRUIDO A TRAVÉS DE SECCIONES MAYORES HISTOLÓGICAS EN SERIE: UN ESTUDIO CADAVÉRICO: El conocimiento anatómico amplio del anorrecto anterior masculino es importante para evitar lesiones de uretra y perforación de recto en la resección interesfinterica o la resección abdominoperineal para cáncer de recto bajo. Sin embargo, su estructura es difícil de entender porque el anorrecto, los músculos y los órganos urogenitales están aliñados en forma complexa tridimensional.

OBJETIVO

Revisar de nuevo el conocimiento anatómico del anorrecto anterior masculino relevante a la resección interesfinterica y la resección abdominoperineal con un enfoque en la morfología muscular espacial. DISEÑO:: Estudio descriptivo cadavérico.

ENTORNO

Ehime y la Universidad de Kyoto.

SUJETOS

Tejido especímenes de nueve cadáveres masculinos. PUNTOS FINALES DE VALORACIÓN:: Las muestras alrededor del anorrecto anterior se seccionaron en serie en planos horizontal, sagital y coronal. Se crearon mayores secciones histológicas en serie a intervalos de 250 μm. Los especímenes fueron teñidos con Elástica van Gieson, y algunas secciones de la serie se estudiaron mediante inmunohistoquímica para detectar músculos lisos y estriados. Dos series fueron digitalizadas y reconstruidas tridimensionalmente.

RESULTADOS

Se demostraron dos regiones sin un borde anatómico definido: (i) la región anterior del esfínter anal externo, donde se entrelazaron el esfínter anal externo, el músculo bulbospongoso y el músculo perineal transverso superficial; y (ii) músculo rectouretral, donde el músculo liso del músculo longitudinal se extiende continuamente a la zona posteroinferior de la uretra, que se acerca más al anorrecto a nivel del ápice prostático. La conexión estrecha entre los músculos estriados y lisos se identificó en la parte anterior del esfínter anal externo superior y la parte anterolateral del nivel del músculo puborrectal. LIMITACIÓN:: Este estudio incluyó una muestra pequeña de cadáveres ancianos. CONCLUSIÓN:: Este estudio aclaró la relación espacial precisa entre los músculos lisos y estriados. Los hallazgos anatómicos detallados ayudarán para una disección anterior paso a paso más precisa en la resección interesfintérica y la resección abdominoperineal, especialmente con el abordaje transanal, que puede magnificar la dirección de las fibras musculares y la contracción del músculo estriado utilizando electroestimulación.

Anatomy of the smooth muscle structure in the female anorectal anterior wall: convergence and anterior extension of the internal anal sphincter and longitudinal muscle

AIM

The anatomy of the region between the vagina and anal canal plays an essential role when performing a proctectomy for low-lying tumours. However, the anatomical characteristics of this area remain unclear. The purpose of the present study was to clarify the configuration, and both lateral and inferior extensions, of the muscle bundles in the anorectal anterior wall in females.

METHODS

Using cadaveric specimens, macroscopic anatomical and histological evaluations were conducted at the anatomy department of our institute. Macroscopic anatomical specimens were obtained from six female cadavers. Histological specimens were obtained from eight female cadavers.

RESULTS

The smooth muscle fibres of the internal anal sphincter and longitudinal muscle extended anteriorly in the anorectal anterior wall of females and the muscle bundles showed a convergent structure. The anterior extending smooth muscle fibres merged into the vaginal smooth muscle layer, distributed subcutaneously in the vaginal vestibule and perineum and spread to cover the anterior surface of the external anal sphincter and the levator ani muscle. Relatively sparse space was observed in the region anterolateral to the rectum on histological analysis.

CONCLUSION

Smooth muscle fibres of the rectum and vagina are intermingled in the median plane, and there is relatively sparse space in the region anterolateral to the rectum. Therefore, when detaching the anorectal canal from the vagina during proctectomy, an approach from both the lateral sides should be used.

Rectal Injury in Radical Perineal Prostatectomy

Objective

To report our experience in treating patients with rectal injury with radical perineal prostatectomy.

Methods

Medical charts of 176 patients submitted to radical perineal prostatectomy from 1996 to 2005 were reviewed to identify rectal problems. A review of rectal injury in prostatectomy is provided.

Results

Of 176 patients who underwent radical perineal prostatectomy, 10 (5.7%) had rectal injury and 4 (2.3%) presented rectal fistula. Two (1.1%) patients were submitted to colostomy. We discuss how to avoid and treat the complications.

Conclusions

There is a real risk of rectal injury during radical perineal prostatectomy, particularly during the learning period or if the approach is not often performed. Fistula might occur, but colostomy is actually unnecessary and rare. A better understanding of the perineal anatomy and knowledge about the technique is recommended before practicing radical perineal prostatectomy.

Descriptive Technique and Initial Results for Robotic Radical Perineal Prostatectomy

OBJECTIVE

To minimize technical challenges of radical perineal prostatectomy (RPP), we conceived and applied the robotic approach to this technique in an aim to improve surgical applicability of RPP. Radical prostatectomy via the perineal route, avoiding the intra-abdominal cavity, has been shown to be oncologically safe, with excellent functional outcomes and a short hospital stay. We report our initial results with this novel approach.

MATERIALS AND METHODS

We performed the procedure in 4 patients. With the patient in the exaggerated lithotomy position, following a 3 cm perineal incision, the initial perineal dissection using Belt's approach is performed, followed by single port placement and docking of the robot.

RESULTS

The median age for patients was 64 years (60-69). Two patients had no rectum because of the abdominoperineal resection due to inflammatory bowel diseases. One of the other 2 patients had a surgical history of aborted robotic-assisted laparoscopic radical prostatectomy and 1 patient had no surgical history. There were no perioperative complications and the patients were discharged within 16-48 hours. Urethral catheter was removed within 10 days in 3 patients, and 3 weeks in 1 patient. Two patients were immediately continent when Foley was removed. The final pathology revealed focally positive margin in those 3 patients who had surgical histories and it was margin negative in the patient with native anatomy. All patients had undetectable prostate-specific antigen postoperatively.

CONCLUSION

RPP was successfully completed in 4 cases, applying a single port robotic perineal approach. Initial results are encouraging, with short hospital stay and minimal postoperative pain.

The male bulbospongiosus muscle and its relation to the external anal sphincter

PURPOSE

The bulbospongiosus muscle is part of the superficial muscular layer of the perineum and pelvic floor. Its morphology remains controversial in the literature. Therefore, we reinvestigated the fascial arrangement and fiber courses of the bulbospongiosus muscle and its topographical relation to the external anal sphincter.

MATERIALS AND METHODS

The perineum was dissected in 9 male cadavers (mean ± SD age 78.3 ± 10.7 years). Select samples were obtained for histology and immunohistochemistry. In 43 patients (mean age 60.7 ± 12 years) the topographical relation between the bulbospongiosus muscle and the external anal sphincter was determined by magnetic resonance imaging.

RESULTS

The perineum contains several fascial layers consisting of elastic and collagen fibers as well as bundles of smooth muscle cells. The bulbospongiosus muscle was subdivided into a ventral and dorsal portion, which developed in 4 variants. The ventral insertion formed a morphological unity with the ischiocavernous muscle while the dorsal origin had a variable relation to the external anal sphincter (5 variants). A muscle-like or connective tissue-like connection was frequently present between the muscles. However, in some cases the muscles were completely separated.

CONCLUSIONS

We suggest a concept of variations of bulbospongiosus muscle morphology that unifies the conflicting literature. Its ventral fiber group and the ischiocavernosus muscle form a functional and morphological unity. While the bulbospongiosus muscle and the external anal sphincter remain independent muscles, their frequent connection might have clinical implications for perineal surgery and anogenital disorders.

The urethral rhabdosphincter, levator ani muscle, and perineal membrane: a review

Detailed knowledge of the anatomy of the rhabdosphincter and adjacent tissues is mandatory during urologic surgery to ensure reliable oncologic and functional outcomes. To characterize the levator ani (LA) function for the urethral sphincter, we described connective tissue morphology between the LA and urethral rhabdosphincter. The interface tissue between the LA and rhabdosphincter area in males contained abundant irregularly arrayed elastic fibers and smooth muscles. The male rhabdosphincter was positioned alongside the LA to divide the elevation force and not in-series along the axis of LA contraction. The male perineal membrane was thin but solid and extends along the inferior margin or bottom of the rhabdosphincter area. In contrast, the female rhabdosphincter, including the compressor urethrae and urethrovaginal sphincter muscles, was embedded in the elastic fiber mesh that is continuous with the thick, multilaminar perineal membrane. The inferomedial edge of the female LA was attached to the upper surface of the perineal membrane and not directly attached to the rhabdosphincter. We presented new diagrams showing the gender differences in topographical anatomy of the LA and rhabdosphincter.

Female longitudinal anal muscles or conjoint longitudinal coats extend into the subcutaneous tissue along the vaginal vestibule: a histological study using human fetuses

PURPOSE

It is still unclear whether the longitudinal anal muscles or conjoint longitudinal coats (CLCs) are attached to the vagina, although such an attachment, if present, would appear to make an important contribution to the integrated supportive system of the female pelvic floor.

MATERIALS AND METHODS

Using immunohistochemistry for smooth muscle actin, we examined semiserial frontal sections of 1) eleven female late-stage fetuses at 28-37 weeks of gestation, 2) two female middle-stage fetus (2 specimens at 13 weeks), and, 3) six male fetuses at 12 and 37 weeks as a comparison of the morphology.

RESULTS

In late-stage female fetuses, the CLCs consistently (11/11) extended into the subcutaneous tissue along the vaginal vestibule on the anterior side of the external anal sphincter. Lateral to the CLCs, the external anal sphincter also extended anteriorly toward the vaginal side walls. The anterior part of the CLCs originated from the perimysium of the levator ani muscle without any contribution of the rectal longitudinal muscle layer. However, in 2 female middle-stage fetuses, smooth muscles along the vestibulum extended superiorly toward the levetor ani sling. In male fetuses, the CLCs were separated from another subcutaneous smooth muscle along the scrotal raphe (posterior parts of the dartos layer) by fatty tissue.

CONCLUSION

In terms of topographical anatomy, the female anterior CLCs are likely to correspond to the lateral extension of the perineal body (a bulky subcutaneous smooth muscle mass present in adult women), supporting the vaginal vestibule by transmission of force from the levator ani.

A single institution study on patient's self-reporting appraisal and functional outcomes of the first set of men following radical perineal prostatectomy

Introduction

This study evaluates the functional outcomes and satisfaction of an initial series of 47 patients after radical perineal prostatectomy performed in our department.

Material and methods

The first set of 47 consecutive patients underwent perineal prostatectomy during 2008 and 2009. Continence, sexual outcomes, and satisfaction of the treatment were evaluated using a self-reporting questionnaire, which was mailed to all patients after 15 to 33 months of follow-up. 26 patients (55.3%) returned a completed form and participated in the study. Additionally, final outcomes were compared to results reported elsewhere.

Results

Amid respondents, 91.7% were satisfied with the chosen treatment and 8.3% regret the previous decision. 38.5% patients reported any urine leakage, 15.4% drip up to 100 ml a day, and only one patient (3.8%) was totally incontinent. 76.9% men report a decline in prior sexual function. Six patients (23.1%) patients have any degree of spontaneous erections and undertake sexual activity. However, as erectile outcomes are adjusted to nine nerve-sparing cases, 66.7% have spontaneous erections and 55.5% undertake sexual activity, but only 40% of them describe their sexual function as satisfying.

Conclusions

Our survey demonstrates that, because of short operating time, fast recovery, low postoperative pain score, early patient mobilization and feeding, and a small (8-10 cm) and inconspicuous skin incision, radical perineal prostatectomy fully deserves to be recognized as a low-morbidity procedure. The perineal approach provides a quality of life and patients satisfaction rate comparable to trendy, highly equipped procedures and emerges as an attractive alternative to them. Even novice “perineal surgeons” may achieve favorable results.

Surgical anatomy of intrapelvic fasciae and vesico-uterine ligament in nerve-sparing radical hysterectomy with fresh cadaver dissections

Radical hysterectomy has been performed for invasive cervical cancer, and autonomic nerve-sparing procedures have been developed to preserve bladder function. To perform and improve the nerve-sparing radical hysterectomy, it is important to understand anatomy of the intra pelvic fasciae, specially vesico-uterine ligament (VUL), because most of injuries to the nerves occurred during incision of the VUL in radical hysterectomy procedures. The objectives of the present study were to provide histological understanding of major structures found in nerve-sparing radical hysterectomy. Serial macroscopic slices (15-20 mm thick) from five female pelves were trimmed and prepared for paraffin-embedded histology. We noted an anatomical entity as "the visceroparietal fascial bridge", which corresponds with the macroscopically identified arcus tendineus fasciae pelvis. A histologically identifiable neurovascular pedicle to the bladder neck corresponded with the deep portion of VUL. These findings could help better preservation of autonomic nerves during radical hysterectomy and improve patient's quality of life after the operation. Translation of surgical anatomy into anatomic terminology enables us to have fruitful discussions with persuasive power by excluding any bias from individual surgeons.

A histotopographic study of the perineal body in elderly women: the surgical applicability of novel histological findings

Female perineal structures located around the perineal body were histologically examined using semiserial sections obtained from 15 elderly female cadavers. The smooth muscle content of the perineal body was greater in multiparous women. The connective tissue of the perineal body extended inferolaterally and provided a fibromuscular mass that was 10-30 mm long mediolaterally and 3-15 mm long superoinferiorly. The lateral extension (LEX) of the perineal body occupies a space that is surrounded by the vestibular bulb, internal anal sphincter, and levator ani slings. The LEX did not directly connect to the ischiopubic bony rami but did connect indirectly via the vestibular bulb and ischiocavernosus. Thus, the LEX appears to play a critical role for maintaining the topographical relationship between the vagina and the rectum. The surgical approximation of bilateral LEX instead of levator ani may be of key importance when doing a perineorrhaphy. As pudendal nerve branches run along the inferior margin of the LEX, a mediolateral episiotomy may not be the best option.

Rectourethralis muscle and pitfalls of anterior perineal dissection in abdominoperineal resection and intersphincteric resection for rectal cancer

When performing nerve-sparing abdominoperitoneal resection or intersphincteric resection of lower rectal cancer, difficulty is sometimes encountered during dissection, separation and treatment in the area anterior to the anorectum passing through the levator hiatus between the bilateral levator ani slings owing to missing the surgical plane or venous bleeding. The rectourethralis muscle, which is a mass of smooth muscle, occupies the levator hiatus. The present histological study using nine male cadaveric specimens demonstrated that: (i) the external anal sphincter is likely to be tightly connected to the rectourethralis muscle; (ii) the rectal muscularis propria communicates with the rectourethralis muscle; (iii) the anorectal veins take a tortuous course across the rectourethralis muscle; (iv) Denonvilliers' fascia ends at the rectourethralis muscle; and (v) the rectourethralis muscle provides posterior attachment for the rhabdosphincter. Moreover, the cavernous nerve has been reported to penetrate the rectourethralis muscle. Therefore, careful treatment of the muscle seems to be necessary to avoid male sexual dysfunction. Owing to muscle fiber communications between the rectal muscularis propria and the rectourethralis muscle, and the fact that Denonvilliers' fascia terminates in the rectourethralis muscle, the surgical plane would tend to deeply penetrate the muscle mass. However, mass ligation of the anterior tissues for control of venous bleeding should be avoided. When the tumor is non-anterior, an abdominal surgical plane behind Denonvilliers' fascia is recommended to avoid excess invasion into the rectourethralis muscle.

AN EMBRYOLOGICAL STUDY OF FETAL DEVELOPMENT OF THE RECTOURETHRALIS MUSCLE—DOES IT REALLY EXIST?

PURPOSE

The so-called rectourethralis muscle is widely described in the urological literature. However, its description is subject to variations concerning extent and morphology. Moreover, little is known about its fetal development, which would allow a better understanding of the adult anatomy. The aim of this study was to investigate the morphology, extent and development of the rectourethralis muscle in fetal specimens.

MATERIALS AND METHODS

A total of 15 normal human male fetuses were included in the study. Age ranged from 13th week of gestation to term. The histological study used plastination and standard and immunohistochemical techniques to identify the developing muscular structures in serial sections of the rectourethral space. Investigations in all 3 planes (coronal, sagittal and transverse) were performed.

RESULTS

In all sections of the proximal aspect of the rectourethral space no developing muscle fibers could be identified leaving the anterior wall of the rectum to join the rhabdosphincter or the apical prostate. In the distal aspect of the rectourethral space an independent muscular structure located between the external muscular layer of the anorectal canal and the dorsal bundles of the rhabdosphincter could be clearly demonstrated. This structure consisted of connective, smooth and striated muscle tissue, and was deeply anchored to the apical perineal body.

CONCLUSIONS

This study suggests that the so-called rectourethralis muscle is a misnomer in the urological literature. In the fetal period a developing muscular structure could be clearly identified as a part of the apical perineal body, which would correspond to the rectoperinealis muscle in the adult.

Variation in course of cavernous nerve with special reference to details of topographic relationships near prostatic apex: Histologic study using male cadavers

OBJECTIVES

To study interindividual variation in the cavernous nerve course near the rhabdosphincter and the apex of the prostate as a basis for refining nerve-sparing radical prostatectomy. The varying anatomy of the cavernous nerve might account for the disparate potency rates after nerve-sparing radical prostatectomy.

METHODS

We examined serial histologic sections from 20 male pelves (7 frontal, 8 sagittal, and 5 axial sections) and performed 5 fresh cadaver dissections.

RESULTS

In the fresh dissections, the macroscopically identified neurovascular bundle consistently showed an almost straight proximal-to-distal course along the urethra. However, on histologic analysis, the types of the nerve course were classified as frontal (2 of 7 specimens), sagittal (3 of 8), and axial (2 of 5). In the frontal and sagittal courses, the nerves passed through the connective tissue of a narrow potential space between the rhabdosphincter and the levator ani. In the specimens showing an axial course, the nerves were spatially distinct from the prostate, coursing ventromedially in the pararectal space. Thus, the nerves could display a long, tortuous course, passing through the rectourethral muscle at its thickest portion. In addition, a nerve component supplying the area of the rhabdosphincter seemed to accompany the cavernous nerve.

CONCLUSIONS

The neurovascular bundle, previously defined in terms of surgery, is likely to differ from the actual course of the cavernous nerve when this is axial, passing through the pararectal space and rectourethral muscle. To avoid cavernous nerve injury, the rectourethral muscle must be managed carefully in both the retropubic and the perineal approaches.

Histotopographic study of the rectourethralis muscle

Radical perineal prostatectomy, relative to retropubic prostatectomy, has become an increasingly used surgical technique for prostate cancer, following advances in laparoscopic methods for pelvic lymph node dissection. Recent protocols of risk stratification may even obviate the need for lymph node dissection. Section of the rectourethralis muscle (RUM) is necessary for access to the retroprostatic space, however, during this procedure rectal injuries may be produced. In this work, we studied the topography and morphology of the RUM, which, despite its importance in perineal surgery, has not been univocally described in the literature. After in situ formalin fixation, the pelvic viscera were removed from 16 male cadavers (age: 54-72 years) and from 4 full-term infants (gestational age: 37-38 weeks). Serial macrosections of the bladder base, prostate gland, and lower rectum cut in horizontal (6 adults and 2 infants) and sagittal (6 adults and 2 infants) planes underwent histological (hematoxylin and eosin, azan-Mallory, and Weigert's staining) and immunohistochemical (anti-smooth muscle actin and anti-sarcomeric actin) study. The remaining 4 adult specimens were cut in horizontal and sagittal planes and plastinated using the epoxy resin E12 sheet procedure. RUM was identified in 10 of 12 (83%) adult specimens and in 4 of 4 (100%) infant specimens. In both sagittal and transverse sections, it showed a triangular-shaped configuration. In all cases, at the level of its posterior portion, fibers continuing with the longitudinal muscular layer of the rectum were visible. In the majority of adult and infant cases, attachment of muscle fibers into the anterior wall of the anal canal was also observed. Anteriorly, the mean (+/-SD) distance between the RUM and the membranous urethra was 5.3 (+/-1.25) mm in adults and 1.0 (+/-0.41) mm in infants. Location of RUM in the prerectal space and the absence of urethral attachment makes the original name of this muscle, "prerectal," by Henle, more correct. In 7 of 10 (70%) adult cases and in 1 of 4 (25%) infant cases, muscle fibers were densely packed along the lateral portions of the RUM, while in its central portion connective tissue was prevalent, with sparse numbers of smooth muscle fibers. Immunohistochemical staining showed that this muscle consists almost entirely of smooth fibers. In all the infant specimens, the RUM was clearly separated from the levator ani, while in 8 of 10 (80%) adult cases, striated fibers of the levator ani and smooth fibers of the RUM intermingled. These structural associations suggest a functional cooperation between the two muscles, particularly in determining the anorectal flexure.

Morphologies of the interfaces between the levator ani muscle and pelvic viscera, with special reference to muscle insertion into the anorectum in elderly Japanese

A specific, smooth muscle-mediated interface between the levator ani muscle (LA) and the pelvic viscera has been reported. Using 110 sagittally trimmed anorectal tissue strips (80 lateral, 15 anterior and 15 dorsal specimens) obtained from the donated cadavers of 46 elderly subjects, we examined variations in the interface between the LA and the rectal muscularis propria, including the so-called conjoined longitudinal muscles. In type A (9/46), little or no tissue connected the LA to the external rectal muscularis propria, but the LA and external sphincteric mass formed a definite complex. In type B (26/46), the covering fascia of the LA changed abruptly into smooth muscles, which merged into the external rectal muscularis propria. In type C (11/46), most of the LA-associated connective tissues, composed of smooth muscles, were tightly connected to the internal and external rectal muscularis propria. These variations seemed to depend on the morphology of the recto-urethralis, the lateral extension of which reinforced the LA-associated smooth muscles sufficiently to form type B and C insertions. We also demonstrated differences in the interfacial tissues between the LA and other pelvic viscera. We hypothesize that, to avoid injury of the LA and its interfaces during strong movement of the pelvic viscera, for example during childbirth, coitus or squeezed evacuation, the pelvic connective tissue-like smooth muscles play an important role as an autonomic buffer and/or modulator of pelvic floor function. Digital examination and transrectal or transvaginal sonography may be useful for evaluating interindividual variation in these interfacial tissues in elderly patients.

Fascial structures and autonomic nerves in the female pelvis: a study using macroscopic slices and their corresponding histology

We investigated the topographical anatomy of the pelvic fasciae and autonomic nerves using macroscopic slices of five decalcified female pelves. The lateral aspect of the supravaginal cervix uteri and superior-most vagina issued abundant thick fiber bundles. These visceral fibrous tissues extended dorsolaterally, joined another fibrous tissue from the rectum (the actual lateral ligament of the rectum) and attached to the parietal fibrous tissues at and around the sciatic foramina (i.e. the sacrospinous ligament, thick fasciae of the coccygeus and piriformis and dorsal end of the covering fascia of the levator ani). The inferior or ventral vagina also issued thick fiber bundles communicating with the levator ani fascia. This connection between the vagina and levator fascia, when stretched, seemed to provide a macroscopic morphology called the arcus tendineus fasciae pelvis. The overall morphology of the visceroparietal fascial bridge exhibited a bilateral wing-like shape. The fascial bridge complex was adjacent but dorso-inferior to the internal iliac vascular sheath and located slightly ventral to the pelvic splanchnic nerve. However, the pelvic plexus and its peripheral branches were embedded in the fascial complex. The hypogastric nerve ran along and beneath the uterosacral peritoneal fold, which did not contain thick fibrous tissue. During surgery, in combination with the superficially located vascular sheath, the morphology of the visceroparietal fascial bridge and associated nerves seemed to be artificially changed and developed into the so-called cardinal, uterosacral, uterovesical and/or rectal lateral ligaments. The classical and original concepts of these pelvic fascial structures may need to be altered to adjust to these surgical observations.