Histotopographic study of the rectourethralis muscle

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.

Complete intersphincteric longitudinal muscle excision May Be key to reducing local recurrence during intersphincteric resection

BACKGROUND

Although total mesorectal excision (TME) is regarded as a standard procedure for rectal cancer, technical definition and evaluation method have not yet been investigated for intersphincteric resection (ISR). This study was performed to introduce a complete ISR procedure, and to assess whether total intersphincteric longitudinal muscle excision (TILME) facilitated the completeness of ISR and reduced recurrence.

METHODS

A total of 1080 patients with rectal adenocarcinoma who underwent robot-assisted low anterior resection (LAR) over 10 years were consecutively enrolled. Propensity-score matching of the two LAR groups (ISR vs LAR group, 1:1) and three ISR subgroups (partial vs subtotal vs total ISR subgroup, 2:2:1) was performed by strict adjustment of baseline characteristics. Archived specimens and video-/photo-records were reevaluated to examine completeness of TILME.

RESULTS

Complete-TILME was performed in 84.5% of patients who underwent ISR. Multivariate analysis showed that incomplete-TILME was the only parameter independently associated with increased 5-year cumulative local recurrence (odds ratio = 23.385; 95% confidence interval = 1.492-366.421; p = 0.03), and that incomplete-TILME was independently associated with adipose tissue surrounding the intersphincteric longitudinal muscle, coloanal anastomosis, and total ISR (p < 0.001-0.05). Although mean incontinence scores and anorectal manometry deteriorated to some degree 12-24 months after surgery in all patients, they remained acceptable. The 5-year cumulative DFS (74.1% vs 60%, p = 0.18) and OS (85.9% vs 70%, p = 0.10) rates tended to be higher in patients with complete than incomplete-TILME.

CONCLUSIONS

The completeness of TILME appears to be an independent indicator of complete ISR, reducing local recurrence following lower rectal cancer surgery.

The series of smooth muscle structures in the pelvic floors of men: Dynamic coordination of smooth and skeletal muscles

Introduction

Recent studies have revealed the extended nature of smooth muscle structures in the pelvic floor, revising the conventional understanding of the “perineal body.” Our aim was to clarify the three‐dimensional configuration and detailed histological properties of the smooth muscle structures in the region anterior to the rectum and anal canal in men.

Materials and methods

Four male cadavers were subjected to macroscopic and immunohistological examinations. The pelvis was dissected from the perineal side, as in the viewing angle during transperineal surgeries. Serial transverse sections of the region anterior to the rectum and anal canal were stained with Masson's trichrome and immunohistological stains to identify connective tissue, smooth muscle, and skeletal muscle.

Results

There was a series of smooth muscle structures continuous with the longitudinal muscle of the rectum in the central region of the pelvic floor, and three representative elements were identified: the anterior bundle of the longitudinal muscle located between the external anal sphincter and bulbospongiosus; bilateral plate‐like structures with transversely‐oriented and dense smooth muscle fibers; and the rectourethral muscle located between the rectum and urethra. In addition, hypertrophic tissue with smooth muscle fibers extended from the longitudinal muscle in the anterolateral portion of the rectum and contacted the levator ani.

Conclusions

The series of smooth muscle structures had fiber orientations and densities that differed among locations. The widespread arrangement of the smooth muscle in the pelvic floor suggests a mechanism of dynamic coordination between the smooth and skeletal muscles.

Essential anatomy for total mesorectal excision and lateral lymph node dissection, in both trans-abdominal and trans-anal perspective

BACKGROUND AND PURPOSE

Total Mesorectal Excisions (TME) is the standard treatment of rectal cancer. It can be performed under laparoscopic, robotic or transanal approach. Inadvertent injury to surrounding structure like autonomic nerves is avoidable, no matter which approach is adopted. Lateral lymph node dissection (LLND) is a less commonly performed pelvic operation involving dissection in an unfamiliar area to most general surgeons. This article aims to clarify all the essential anatomy related to these procedures.

METHODS

We performed thorough literature search and revision on the pelvic anatomy. Our cases of TME and LLND, under either laparoscopic or transanal approach, were reviewed. We integrated the knowledge from literatures and our own experience. The result was presented in details, together with original figures and intra-operative photos.

MAIN FINDINGS

Anatomy of pelvic fascia, autonomic nerve system, anal canal and sphincter complex are core knowledge in performing TME and LLND.

CONCLUSIONS

Thorough understanding of the pelvic anatomy enables colorectal surgeons to master these procedures, avoid complication and perform extended resection. On the other hand, surgeons can appreciate the complex pelvic anatomy easier by seeing the pelvis in opposite angles (transabdominal and transaanal view).

Spatial distribution of smooth muscle tissue in the female pelvic floor and surrounding the urethra and vagina

Data regarding urethral supporting structures are insufficient for understanding the mechanism of stress urinary incontinence. Whether smooth muscle fibers contribute to urethral support and pelvic floor support structures is unclear. This study aimed to clarify the histological structures and spatial distributions of smooth muscle tissues surrounding the urethra and vagina. Using cadaveric specimens, macroscopic anatomical and histological evaluations were conducted. Six female cadavers were used for macroscopic observations. Ten female cadavers were used for histological observations. Three pelvises were cut in a plane vertical to the urethra, and the other pelvises were cut in a plane parallel to the urethra and vagina to observe tissues surrounding the urethra and vagina. The major tissue component around the proper muscle layer of the urethra was smooth muscle tissue, which mediated among the urethra, pubis, and levator ani. Smooth muscle tissues laterally extended the smooth muscle fibers, both superiorly and inferiorly toward the levator ani, with a few fibers inserted in the levator ani. Smooth muscle was found between the urethral walls and pubic bones. Smooth muscle may contribute to the mechanism of pelvic floor support.

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.

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.

Treatment of large avulsion injury in perianal, sacral, and perineal regions by island flaps or skin graft combined with vacuum assisted closure

BACKGROUND

Traumatic avulsion injuries to the anus, although uncommon, can result in serious complications and even death. Management of anal avulsion injuries remains controversial and challenging. This study aimed to investigate the clinical effects of treating large skin and subcutaneous tissue avulsion injuries in the perianal, sacral, and perineal regions with island flaps or skin graft combined with vacuum assisted closure.

METHODS

Island flaps or skin graft combined with vacuum assisted closure, diverting ileostomy, the rectum packed with double-lumen tubes around Vaseline gauze, negative pressure drainage with continuous distal washing, wounds with skin grafting as well as specialized treatment were performed.

RESULTS

The injuries healed in all patients. Six cases had incomplete perianal avulsion without wound infection. Wound infection was seen in four cases with annular perianal avulsion and was controlled, and the separated prowl lacuna was closed. The survival rate in 10 patients who underwent skin grafting was higher than 90%. No anal stenosis was observed after surgery, and ileostomy closure was performed at 3 months (six cases) and 6 months (four cases) after surgery, respectively.

CONCLUSIONS

Covering a wound with an island flap or skin graft combined with vacuum assisted closure is successful in solving technical problems, protects the function of the anus and rapidly seals the wound at the same time.

Architecture of structures in the urogenital triangle of young adult males; comparison with females

The fibro‐muscular architecture of the urogenital triangle remains contentious. Reasons are small size of the constituting structures and poor visibility with most imaging methods. We reinvestigated the area in serial sections of three males (21–38 years old) of the American and Chinese Visible Human Projects and two 26‐week‐old male fetuses, and compared the findings with earlier observations in females. The mass of the levator ani muscle was approximately twofold smaller and its funnel shape steeper in males than females. In the levator hiatus, a strand of the smooth longitudinal muscle layer of the rectum, the ‘rectourethral (RU) muscle’, extended anteriorly from the anorectal bend to the penile bulb. Fibrous tissue that formed in the inferior reach of the fetal RU muscle identified the location of the developing perineal body (PB) and divided the muscle into posterior ‘rectoperineal’ and anterior ‘deep perineal’ portions. In males, the PB remained small and bipartite, so that the RU muscle presented as an undivided midline structure. The well‐developed female PB, instead, intertwined with the deep perineal muscle and both structures passed the vagina bilaterally to form the perineal membrane in the posterior portion of the urogenital triangle. The urethral rhabdosphincter extended in the anterior portion of the urogenital triangle between the penile bulb inferiorly and the bladder neck superiorly, and consisted of a well‐developed circular ‘membranous’ portion with bilateral posteroinferior ‘wings’ and a thinner ‘prostatic’ portion on the prostate anterior side. In men, muscles occupy the urogenital triangle, but additional tightening of the locally fibrous adipose tissue by the superficial transverse perineal muscle appears necessary to generate functional support in women. An interactive 3D pdf file with these anatomical details (available online) should allow more accurate interpretation of ultrasound, computed tomography and magnetic resonance images.

Essential Anatomy of the Anorectum for Colorectal Surgeons Focused on the Gross Anatomy and Histologic Findings

The anorectum is a region with a very complex structure, and surgery for benign or malignant disease of the anorectum is impossible without accurate anatomical knowledge. The conjoined longitudinal muscle consists of smooth muscle from the longitudinal muscle of the rectum and the striate muscle from the levator ani and helps maintain continence; the rectourethralis muscle is connected directly to the conjoined longitudinal muscle at the top of the external anal sphincter. Preserving the rectourethralis muscle without damage to the carvernous nerve or veins passing through it when the abdominoperineal resection is implemented is important. The mesorectal fascia is a multi-layered membrane that surrounds the mesorectum. Because the autonomic nerves also pass between the mesorectal fascia and the parietal fascia, a sharp pelvic dissection must be made along the anatomic fascial plane. With the development of pelvic structure anatomy, we can understand better how we can remove the tumor and the surrounding metastatic lymph nodes without damaging the neural structure. However, because the anorectal anatomy is not yet fully understood, we hope that additional studies of anatomy will enable anorectal surgery to be performed based on complete anatomical knowledge.

The utility of plastinates in court: a case of firearm homicide

Plastination is a technique renowned for its use in the preservation of human tissues or organs, and is mainly employed in anatomical training and in research regarding various scientific fields. The advantages of this method are related to the natural appearance, absence of odor, and easy-handling of the plastinated products. The use of plastinates in forensic sciences, their potential role in personal identification, and their usefulness in interpretation of post-mortem findings has been described, although literature on this topic is poor. The present paper is the first report of a firearm homicide where the brain of the victim was plastinated and presented in court as documentary evidence. Three dimensional examination of the brain during the trial allowed the judge to directly evaluate the pathway of the projectile and to compare it with the information that was presented based on depositions, post mortem data and police investigations, in a more straightforward manner. The important role played by plastination in the reported case in assisting with the final verdict could be a catalyst to extend the use of this technique to other criminal cases.

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.

Use of a novel absorbable barbed plastic surgical suture enables a "self-cinching" technique of vesicourethral anastomosis during robot-assisted prostatectomy and improves anastomotic times

PURPOSE

To demonstrate a novel technique of self-cinching anastomosis using a barbed and looped suture during robot-assisted radical prostatectomy (RARP).

PATIENTS AND METHODS

This is a feasibility study of 50 consecutive patients who underwent this novel self-cinching anastomotic technique using a V-Loc™ 180 absorbable barbed suture after RARP for clinically localized prostate cancer. The results were then compared with 50 consecutive patients who underwent RARP by the same surgeon before this new technique. We examined whether this novel technique had any effects on posterior reconstruction time, vesicourethral anastomosis time, and thus total reconstruction and operative time by inference.

RESULTS

The V-Loc 180 group had significantly shorter posterior reconstruction (40 seconds vs 60 seconds; P ≤ 0.001) and vesicourethral anastomotic times (7 min vs 12 min; P ≤ 0.001). By inference, this meant that total reconstruction and operative times were also significantly less (8 minutes vs 13.5 min; P ≤ 0.001 and 106 min vs 114.5 minutes; P ≤ 0.001, respectively).

CONCLUSION

We have shown that this technique is feasible and improves posterior reconstruction and anastomotic times. Further follow-up will determine any benefits of this technique on anastomotic urinary leak rates, continence, and catheter removal times.

The male rectourethralis and deep transverse perineal muscles and their relationship to adjacent structures examined with successive slices of celloidin-embedded pelvic viscera

BACKGROUND

The precise relationship of the structures dorsal to the membranous urethra, including the rectourethralis muscle, the rhabdosphincter, the deep transverse perineal muscle (DTPM), the perineal body, and Denonvillier's fascia, remains controversial.

OBJECTIVE

Our aim was to reexamine the detailed anatomy of the rectourethralis muscle and the deep transverse perineal muscle and their relationship with adjacent structures.

DESIGN, SETTING, AND PARTICIPANTS

The pelvic viscera, including bladder, prostate, and rectum, were obtained from 20 formalin-fixed adult male cadavers.

MEASUREMENTS

The pelvic viscera were embedded in celloidin and then cut into successive slices with an immersing-alcohol microtome. All slices were explored with anatomic microscopy.

RESULTS AND LIMITATIONS

The longitudinal muscle of the anterior rectal wall was divided into anterior and posterior bundles at the junction of the rectum and anal canal. The intermediate fibers of the anterior bundle ended at the perineal body. The lateral fibers of the anterior bundle terminated at the posterior connective tissue of the bulbus penis. The DTPM occupied the space between the rhabdosphincter, rectum, and the bilateral levator ani muscle. Denonvillier's fascia terminated at the junction of the prostate and rhabdosphincter. Numerous slender nerves coming from the neurovascular bundle perforated the DTPM.

CONCLUSIONS

The anterior bundle of the longitudinal muscle of the rectum inserts into the bulbus penis forming the rectourethralis muscle and ends at the perineal body forming the rectoperinealis muscle. The anterior bundle and DTPM together may contribute to the rectal angle of the anterior rectal wall, and they support the posterior border of the rhabdosphincter.

A critical analysis of the current knowledge of surgical anatomy related to optimization of cancer control and preservation of continence and erection in candidates for radical prostatectomy

CONTEXT

Detailed knowledge of the anatomy of the prostate and adjacent tissues is mandatory during radical prostatectomy to ensure reliable oncologic and functional outcomes.

OBJECTIVE

To review critically and to summarize the available literature on surgical anatomy of the prostate and adjacent structures involved in cancer control, erectile function, and urinary continence.

EVIDENCE ACQUISITION

A search of the PubMed database was performed using the keywords radical prostatectomy, anatomy, neurovascular bundle, fascia, pelvis, and sphincter. Relevant articles and textbook chapters were reviewed, analyzed, and summarized.

EVIDENCE SYNTHESIS

Anatomy of the prostate and the adjacent tissues varies substantially. The fascia surrounding the prostate is multilayered, sometimes either fused with the prostate capsule or clearly separated from the capsule as a reflection of interindividual variations. The neurovascular bundle (NVB) is situated between the fascial layers covering the prostate. The NVB is composed of numerous nerve fibers superimposed on a scaffold of veins, arteries, and variable amounts of adipose tissue surrounding almost the entire lateral and posterior surfaces of the prostate. The NVB is also in close, cage-like contact to the seminal vesicles. The external urethral sphincter is a complex structure in close anatomic and functional relationship to the pelvic floor, and its fragile innervation is in close association to the prostate apex. Finally, the shape and size of the prostate can significantly modify the anatomy of the NVB, the urethral sphincter, the dorsal vascular complex, and the pubovesical/puboprostatic ligaments.

CONCLUSIONS

The surgical anatomy of the prostate and adjacent tissues involved in radical prostatectomy is complex. Precise knowledge of all relevant anatomic structures facilitates surgical orientation and dissection during radical prostatectomy and ideally translates into both superior rates of cancer control and improved functional outcomes postoperatively.

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.