The dispute about the external sphincter and the urogenital diaphragm

Anatomy of muscle connections in the male urethra and anorectal canal

OBJECTIVES

To elucidate the male urethral muscular structure and its relationship with the anorectal canal muscles, as establishing an anatomical foundation for urethral function will contribute to the prevention, diagnosis, and treatment of urinary incontinence.

METHODS

Eight male cadavers were used. Using a multifaceted approach, we performed macroscopic anatomical examination, histological analysis of wide-range serial sectioning and immunostaining, and three-dimensional (3D) reconstruction from histological sections. In the macroscopic anatomical examination, pelvic halves were meticulously dissected in layers from the medial aspect. In the histological analysis, the tissue, including the urethra and anorectal canal, was serially sectioned in the horizontal plane. The muscular structures were reconstructed and visualised in 3D.

RESULTS

The membranous portion of the urethra had three muscle layers: the longitudinal and circular muscles (smooth muscle) and the external urethral sphincter (skeletal muscle). The circular muscle was connected posteriorly to the longitudinal rectal muscle. The external urethral sphincter had a horseshoe shape, with its posterior ends continuing to the external anal sphincter, forming a 3D ring-like sphincter.

CONCLUSION

This study revealed skeletal and smooth muscle connections between the male urethra and anorectal canal, enabling urethral compression and closure. These anatomical muscle connections suggest a functional linkage between them.

Imaging the levator ani and the puborectalis muscle: implications in understanding regional anatomy, physiology and pathology

Purpose:To review the findings of recent dynamic imaging of the levator ani muscle in order to explain its function during defecation. Historical anatomical studies have suggested that the levator ani initiates defecation by lifting the anal canal, with conventional dissections and static radiologic imagery having been equated with manometry and electromyography.Materials and methods:An analysis of the literature was made concerning the chronological development of imaging modalities specifically designed to assess pelvic floor dynamics. Comparisons are made between imaging and electromyographic data at rest and during provocative manoeuvres including squeeze and strain.Results:The puborectalis muscle is shown distinctly separate from the levator ani and the deep external anal sphincter. In contrast to conventional teaching that the levator ani initiates defecation by lifting the anus, dynamic illustration defecography (DID) has confirmed that the abdominal musculature and the diaphragm instigate defecation with the transverse and vertical component portions of the levator ani resulting in descent of the anus. Current imaging has shown a tendinous peripheral structure to the termination of the conjoint longitudinal muscle, clarifying the anatomy of the perianal spaces. Planar oXy defecography has established patterns of movement of the anorectal junction that separate controls from those presenting with descending perineum syndrome or with anismus (paradoxical puborectalis spasm).Conclusions:Dynamic imaging of the pelvic floor (now mostly with MR proctography) has clarified the integral role of the levator ani during defecation. Rather than lifting the rectum, the muscle ensures descent of the anal canal.

Imaging of the Bulbourethral (Cowper) Gland: Abnormalities and Differential Diagnosis

Normal Cowper glands and ducts are imperceptible at imaging. However, abnormalities of the Cowper glands and ducts are increasingly seen owing to increasing use of cross-sectional imaging. In this article, the authors present a comprehensive review of the normal anatomy of the Cowper glands and ducts and the clinical and imaging findings of conditions that affect them in an effort to help lead to appropriate diagnosis and management. A Cowper duct syringocele is a congenital or acquired dilatation of the Cowper duct in the bulb of the corpus spongiosum. Retrograde urethrography is the standard test to diagnose a communicating (open) Cowper duct syringocele, and MRI is used for further morphologic assessment. Cowperitis refers to inflammation of the gland and/or duct, and recurrent cowperitis is usually associated with an underlying syringocele, a urethral fistulous connection to the Cowper gland, or a perianal fistula. MRI allows detection of the underlying structural abnormality and the superimposed inflammation. Cowper stones are typically radiopaque and are found in both the Cowper gland and duct. A Cowper gland HHhemorrhagic cyst may be incidentally detected at MRI of the prostate, and follow-up MRI may be required to ensure evolution of hemorrhage and exclude an underlying neoplasm. Cowper gland carcinoma is rare and includes adenocarcinoma and adenoid cystic carcinoma subtypes. Transperineal US may be used for initial evaluation and CT and/or MRI are necessary for further characterization and staging. Cowper gland hyperplasia is a rare entity with few previous reports that may be incidentally detected at imaging and may mimic malignancy. ^©RSNA, 2022.

Psychosocial Distress in the Early Recovery Period after Radical Prostatectomy

PURPOSE

This study aimed to evaluate psychosocial distress in the context of continence and oncological outcome during the early recovery period after radical prostatectomy (RP) for prostate cancer.

PATIENTS AND METHODS

Retrospectively collected data from 587 patients who underwent inpatient rehabilitation after RP in 2016 and 2017 were analyzed. Psychosocial distress (measured by using a Questionnaire on Stress in Cancer Patients [QSC-R10]) and continence status (urine loss on a 24-h pad test and urine volume on uroflowmetry) were evaluated at the beginning (T1) and end (T2) of a 3-week inpatient rehabilitation. Multivariate logistic regression was performed to identify predictors for high distress (QSC-R10 score ≥15).

RESULTS

The median patient age was 65 years. At the start of rehabilitation, 204 patients (34.8%) demonstrated high distress. Psychosocial distress decreased significantly (p < 0.001) from a median of 11.0 at T1 (median 16 days after surgery) to a median of 6.0 at T2 (median 37 days after surgery). Complete continence increased significantly (p < 0.001) from 39.0% at T1 to 58.9% at T2. The median urine volume increased significantly (p < 0.001) from 161 mL at T1 to 230 mL at T2. Often, distress is higher in younger patients, whereas incontinence is higher in older patients. Multivariate logistic regression analysis identified age ≤69 years (p = 0.001) and tumor stage ≥pT3 (p = 0.006) as independent predictors of high distress.

CONCLUSIONS

Distress and incontinence decreased significantly during the 3 weeks of inpatient rehabilitation after RP. Patient age ≤69 years and tumor stage ≥pT3 are independent predictors of high psychosocial distress.

The distribution pattern of periprostatic neurovascular bundles examined with successive celloidin slices

Background

Although several distribution patterns of periprostatic neurovascular bundles have been proposed, variant dissection technique based on these patterns still confused surgeons. The aim of this study was to describe the periprostatic neurovascular bundles and their relationship with the fascicles around prostate and provide the accurate morphologic knowledge of periprostatic tissue for prostate operation.

Methods

The pelvic viscera were obtained from 26 adult male cadavers. They were embedded in celloidin and cut into successive slices. The slices were explored with anatomic microscopy. 3-Dimensional reconstruction was achieved with celloidin sections and series software.

Results

The prostatic capsule which surrounded the dorsal, bilateral aspect of the prostate was attached ventrally to anterior fibrous muscular stroma (AFMS). The lower part of the striated sphincter completely embraced the urethral; the upper part of this muscle covered the lower ventral surface of prostate. The upper ventral surface of prostate is covered by the circular muscle of detrusor. The levator fascia and the capsule adhered on the most convex region of the lateral prostate, but separated on the other region. The pelvic neurovascular bundles (PNVB) divided into the anterior and posterior divisions. The anterior division continued as dorsal vascular complex (DVC). The distal part of DVC entered into penile hilum. The posterior division continued as neurovascular bundles, and then as the cavernous supply (CS). The distal part of CS joined into pudendal neurovascular bundles.

Conclusions

The capsule and AFMS formed a pocket like complex. There were anterior and posterior neurovascular approaches from PNVB to penile hilum.

Interactive three-dimensional teaching models of the female and male pelvic floor

Controversies regarding structure and function of the pelvic floor persist because of its poor accessibility and complex anatomical architecture. Most data are based on dissection. This "surgical" approach requires profound prior knowledge, because applying the scalpel precludes a "second look." The "sectional" approach does not entail these limitations, but requires segmentation of structures and three-dimensional reconstruction. This approach has produced several "Visible Human Projects." We dealt with limited spatial resolution and difficult-to-segment structures by proceeding from clear-cut to more fuzzy boundaries and comparing segmentation between investigators. We observed that the bicipital levator ani muscle consisted of pubovisceral and puborectal portions; that the pubovisceral muscle formed, together with rectococcygeal and rectoperineal muscles, a rectal diaphragm; that the external anal sphincter consisted of its subcutaneous portion and the puborectal muscle only; that the striated urethral sphincter had three parts, of which the middle (urethral compressor) was best developed in females and the circular lower ("membranous") best in males; that the rectourethral muscle, an anterior extension of the rectal longitudinal smooth muscle, developed a fibrous node in its center (perineal body); that the perineal body was much better developed in females than males, so that the rectourethral subdivision into posterior rectoperineal and anterior deep perineal muscles was more obvious in females; that the superficial transverse perineal muscle attached to the fibrous septa of the ischioanal fat; and that the uterosacral ligaments and mesorectal fascia colocalized. To facilitate comprehension of the modified topography we provide interactive 3D-PDFs that are freely available for teaching purposes. Clin. Anat. 33:275-285, 2020. © 2019 Wiley Periodicals, Inc.

Functional recovery after radical prostatectomy for prostate cancer

With the enthusiasm regarding robotic application in radical prostatectomy in accordance with the widespread use of serum prostate-specific antigen as a screening test, the number of surgeries performed for complete removal of the gland is increasing continuously. However, owing to the adjacent anatomical location of the prostate to the nerve and urethral sphincter complex, functional recovery, namely improvement from post-prostatectomy incontinence (PPI) and post-prostatectomy erectile dysfunction, still remains a main problem for patients who are reluctant to undergo surgery and tend to choose alternative ways instead. Since the late 1980s, the introduction of radical prostatectomy by open surgical modalities, the depth of the anatomical understanding of the structure surrounding the prostate is getting tremendous, which leads to the development of new surgical modalities and techniques that are consequently aimed at reducing the incidences of PPI and erectile dysfunction. Briefly, recent data from robotic radical prostatectomy, particularly on PPI, are quite acceptable, but by contrast, the reported potency regain rate still remains <20%, which indicates the need for advanced surgical modification to overcome it. In this review, the authors summarized the recent findings on the anatomy and surgical techniques reported up to now.

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.

Architectural differences in the anterior and middle compartments of the pelvic floor of young-adult and postmenopausal females

The pelvic floor guards the passage of the pelvic organs to the exterior. The near-epidemic prevalence of incontinence in women continues to generate interest in the functional anatomy of the pelvic floor. However, due to its complex architecture and poor accessibility, the classical 'dissectional' approach has been unable to come up with a satisfactory description, so that many aspects of its anatomy continue to raise debate. For this reason, we opted for a 'sectional' approach, using the Chinese Visible Human project (four females, 21-35 years) and the Visible Human Project (USA; one female, 59 years) datasets to investigate age-related changes in the architecture of the anterior and middle compartments of the pelvic floor. The puborectal component of the levator ani muscle defined the levator hiatus boundary. The urethral sphincter complex consisted of a circular proximal portion (urethral sphincter proper), a sling that passed on the vaginal wall laterally to attach to the puborectal muscle (urethral compressor), and a circular portion that surrounded the distal urethra and vagina (urethrovaginal sphincter). The exclusive attachment of the urethral sphincter to soft tissues implies dependence on pelvic-floor integrity for optimal function. The vagina was circular at the introitus and gradually flattened between bladder and rectum. Well-developed fibrous tissue connected the inferior vaginal wall with urethra, rectum and pelvic floor. With eight-muscle insertions, the perineal body was a strong, irregular fibrous node that guarded the levator hiatus. Only loose areolar tissue comprising a remarkably well developed venous plexus connecting the middle and superior parts of the vagina with the lateral pelvic wall. The posterolateral boundary of the putative cardinal and sacrouterine ligaments coincided with the adventitia surrounding the mesorectum. The major difference between the young-adult and postmenopausal pelvic floor was the expansion of fat in between the components of the pelvic floor. We hypothesize that accumulation of pelvic fat compromises pelvic-floor cohesion, because the pre-pubertal pelvis contains very little fibrous and adipose tissue, and fat is an excellent lubricant.

Injury in Pelvic Fracture Urethral Injury Is Membranobulbar: Fact or Myth

Pelvic fracture urethral injuries commonly result from motor vehicle collisions, and the mechanism of injury conventionally thought was a shearing injury at the membranous urethra, which would destroy the striated sphincter. Continence would therefore depend on the bladder neck. Striated sphincter and the site of injury have not been shown clearly on preoperative imaging. We demonstrate our protocol of performing magnetic resonance imaging whereby the membranous sphincter is seen intact and the injury is shown to be at the membranobulbar junction contrary to conventional belief. This suggests that surgical reconstruction can be undertaken, preserving both sphincter mechanisms and improving postoperative continence.

Perineal body anatomy seen by three-dimensional endovaginal ultrasound of asymptomatic nulliparae

AIM

The perineal body (PB) plays an important role in supporting the pelvic floor and the posterior vaginal wall, but its attachments and relationships are still debated. This study aimed to assess the normal anatomy of the PB using high-resolution three-dimensional endovaginal ultrasound (3D-EVUS) in asymptomatic nulliparae.

METHOD

To validate the identification of perineal structures, 3D-EVUS was initially performed on nulliparous cadavers. Fresh frozen pelves were prepared and echogenic structures thought to be the PB, the external anal sphincter, the superficial and deep transverse perineii, pubovaginalis, puboperinealis, puboanalis, puborectalis and iliococcygeus muscles were tagged with biopsy needles, and marked with indigo carmine dye for localization during dissection. In the second part of the study, consecutive asymptomatic nulliparae were prospectively imaged with the same ultrasound modality. Interrater reproducibility was assessed off-line from stored 3D US volumes using a standardized technique.

RESULTS

Five fresh frozen pelves and 44 asymptomatic nulliparae were assessed with 3D-EVUS. The PB was seen as an ovoid structure of mixed echogenicity between the rectum and vagina. It appeared to be divided into a superficial level, in contact with the external anal sphincter, the bulbospongiousus and the superficial transverse perineii muscle and a deep level, in contact with puboperinealis and puboanalis muscles. Interobserver repeatability was excellent for the measurements of PB height [intraclass correlation coefficient (ICC) 0.927], PB depth (ICC 0.969) and PB width (ICC 0.932).

CONCLUSION

The PB is divided into two levels with different anatomical relationships with the pelvic floor muscles. 3D-EVUS yields reproducible assessment of this complex structure.

A Critical Analysis of the Current Knowledge of Surgical Anatomy of the Prostate Related to Optimisation of Cancer Control and Preservation of Continence and Erection in Candidates for Radical Prostatectomy: An Update

CONTEXT

In 2010, we published a review summarising the available literature on surgical anatomy of the prostate and adjacent structures involved in cancer control and the functional outcome of prostatectomy.

OBJECTIVE

To provide an update based on new literature to help the surgeon improve oncologic and surgical outcomes of radical prostatectomy (RP).

EVIDENCE ACQUISITION

We searched the PubMed database using the keywords radical prostatectomy, anatomy, neurovascular bundle, nerve, fascia, pelvis, sphincter, urethra, urinary continence, and erectile function. Relevant articles and textbook chapters published since the last review were critically reviewed, analysed, and summarised. Moreover, we integrated aspects that were not addressed in the last review into this update.

EVIDENCE SYNTHESIS

We found new evidence for several topics. Up to 40% of the cross-sectional surface area of the urethral sphincter tissue is laterally overlapped by the dorsal vascular complex and might be injured during en bloc ligation. Denonvilliers fascia is fused with the base of the prostate in a horizontal fashion dorsally/caudally of the seminal vesicles, requiring sharp detachment when preserved. During extended pelvic lymph node dissection, the erectile nerves are at risk in the presacral and internal iliac area. Dissection planes for nerve sparing can be graded according to the amount of tissue left on the prostate as a safety margin against positive surgical margins. Vascular structures can serve as landmarks. The urethral sphincter and its length after RP are influenced by the shape of the apex. Taking this shape into account allows preservation of additional sphincter length with improved postoperative continence.

CONCLUSIONS

This update provides additional, detailed information about the surgical anatomy of the prostate and adjacent tissues involved in RP. This anatomy remains complex and widely variable. These details facilitate surgical orientation and dissection during RP and ideally should translate into improved outcomes.

PATIENT SUMMARY

Based on recent anatomic findings regarding the prostate and its surrounding tissue, the urologist can individualise the dissection during RP according to cancer and patient characteristics to improve oncologic and functional results at the same time.

Development of a novel classification system for anatomical variants of the puboprostatic ligaments with expert validation

INTRODUCTION

We propose a novel classification system with a validation study to help clinicians identify and typify commonly seen variants of the puboprostatic ligaments (PPL).

METHODS

A preliminary dissection of 6 male cadavers and a prospective dataset of over 300 robotic-assisted laparoscopic radical prostatectomies (RARP) recorded on video were used to identify 4 distinct ligament types. Then the prospectively collected database of surgical videos was used to isolate images of the PPL from RARP. Over 300 surgical videos were reviewed and classified with 1 to 5 pictures saved for reference of the type of PPL. To validate the new classification system, we selected 5 independent, blinded expert robotic surgeons to classify 100 ligaments based on morphology into a 4-type system: parallel, V-shaped, inverted V-shape, and fused. One week later, a subset of 25 photographs was sent to the same experts and classified. Statistical analyses were performed to determine both the intra-rater and inter-rater reliability of the proposed system.

RESULTS

Inverted V-shaped ligaments were noted most frequently (29.97%), parallel and V-shaped ligaments were found at 19.19% and 11.11%, respectively and fused ligaments were noted less frequently (6.06%). There was good intra-rater agreement (κ = 0.66) and inter-rater agreement (κ = 0.67) for the classification system.

CONCLUSIONS

This classification system provided standardized descriptions of ligament variations that could be adopted universally to help clinicians categorize the variants. The system, validated by several blinded expert surgeons, demonstrated that surgeons were able to learn and correctly classify the variants. The system may be useful in helping to predict peri- and postoperative outcomes; however, this will require further study.

Newer and novel artificial urinary sphincters (AUS): the development of alternatives to the current AUS device

INTRODUCTION

The current artificial urinary sphincter (AUS), AMS 800 (American Medical Systems, Minnesota, MN, USA) is considered the standard of care for the treatment of urinary incontinence (UI). While the long-term effectiveness, safety, and durability of the current model of the AMS 800 are well documented, it is not without its limitations and complications. Over the last few years, improvements in design and innovative research into AUS devices have increased the treatment arsenal in male UI.

METHODS

Articles from peer-reviewed journals, abstracts from scientific meetings and electronic literature searches formed the basis of this review.

RESULTS

Newer AUS models, e.g. FlowSecure, Zephyr, Pro-ACT and other novel experimental AUS devices, are designed to simulate a healthy human sphincter and address the limitation of the existing AMS 800 device.

CONCLUSIONS

Newer and novel AUS models are innovative and showed promising outcomes in short- to intermediate-term follow-up. However, there exists the need for prospective randomised clinical trials and complete reporting of adverse and long-term results before these AUS models can replace the existing AMS 800 device.

Fetal topographical anatomy of the female urethra and descending vagina: a histological study of the early human fetal urethra

BACKGROUND

Which parts of the male urethra correspond to the female urethra? To resolve this question, we need to understand fetal topographical changes in the urethra, its external sphincter and vagina. The vagina joins the mid-course of the primitive urethra and, later "descends" to the vaginal vestibulum.

METHODS

We examined histological sections of 14 female and 4 male mid-term fetuses.

RESULTS

The inferior end of the vagina was consistently embedded in the posterior wall of the urethra at 9-12 weeks. The supero-inferior level of the vaginal merging was lower in larger fetuses. Thus, the sequential variation in levels appeared to reflect the process of vaginal descent. However, in spite of penetration of the vaginal end into the posterior urethral wall, we found no sign of destruction of the urethral wall after vaginal descent in the low-merging types. Before vaginal descent, the female external sphincter extended posterolaterally around the urethra.

CONCLUSION

The vaginal descent is classically regarded as a relative topographical change, but it is likely to be a result of elongation of the proximal urethra in the superior side of the vaginal merging. Conversely, the distal urethra is likely to be incorporated into the vaginal vestibulum by 15 weeks. During these processes, most of the female external sphincter seems to be expelled from the original anterior position into the vestibular wall as the urethrovaginal sphincter. The adult female urethra seems to correspond to the male prostatic urethra superior to the prostatic colliculus.

Anatomy and histology of the lower urinary tract

The function of the lower urinary tract is basically storage of urine in the bladder and the at-will periodic evacuation of the stored urine. Urinary incontinence is one of the most common lower urinary tract disorders in adults, but especially in the elderly female. The urethra, its sphincters, and the pelvic floor are key structures in the achievement of continence, but their basic anatomy is little known and, to some extent, still incompletely understood. Because questions with respect to continence arise from human morbidity, but are often investigated in rodent animal models, we present findings in human and rodent anatomy and histology. Differences between males and females in the role that the pelvic floor plays in the maintenance of continence are described. Furthermore, we briefly describe the embryologic origin of ureters, bladder, and urethra, because the developmental origin of structures such as the vesicoureteral junction, the bladder trigone, and the penile urethra are often invoked to explain (clinical) observations. As the human pelvic floor has acquired features in evolution that are typical for a species with bipedal movement, we also compare the pelvic floor of humans with that of rodents to better understand the rodent (or any other quadruped, for that matter) as an experimental model species. The general conclusion is that the "Bauplan" is well conserved, even though its common features are sometimes difficult to discern.

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.

Intergender differences in histological architecture of the fascia pelvis parietalis: a cadaveric study

The fascia pelvis parietalis (FPP) or endopelvic fascia is a well-known structure, but few studies described the detailed histological architecture, including the composite fiber directions. We hypothesized a gender-specific fiber architecture corresponding to the functional demand. For the first step to examine this hypothesis, we investigated specimens from 27 adult cadavers (10 males and 17 females) and 11 midterm fetuses (five males and six females) using immunohistochemistry and aldehyde-fuchsin staining. The adult female FPP was a solid, thick monolayered structure that was reinforced by abundant elastic fibers running across the striated muscle fibers, but it contained little or no smooth muscles (SM). In contrast, the male FPP was multilayered with abundant SM. In midterm fetuses, SM originated from the inferior part of the bladder and extended inferiorly along the gender-specific courses. Thus, we found a clear intergender difference in FPP architecture. However, the functional significance remained unknown because the basic architecture was common between nulliparous and multiparous women. Rather than for meeting the likely mechanical demands of pregnancy and vaginal delivery, the intergender difference of the FPP seemed to result from differences in the amount and migration course of bladder-derived SM as well as in hormonal background.

Neural control of the female urethral and anal rhabdosphincters and pelvic floor muscles

The urethral rhabdosphincter and pelvic floor muscles are important in maintenance of urinary continence and in preventing descent of pelvic organs [i.e., pelvic organ prolapse (POP)]. Despite its clinical importance and complexity, a comprehensive review of neural control of the rhabdosphincter and pelvic floor muscles is lacking. The present review places historical and recent basic science findings on neural control into the context of functional anatomy of the pelvic muscles and their coordination with visceral function and correlates basic science findings with clinical findings when possible. This review briefly describes the striated muscles of the pelvis and then provides details on the peripheral innervation and, in particular, the contributions of the pudendal and levator ani nerves to the function of the various pelvic muscles. The locations and unique phenotypic characteristics of rhabdosphincter motor neurons located in Onuf's nucleus, and levator ani motor neurons located diffusely in the sacral ventral horn, are provided along with the locations and phenotypes of primary afferent neurons that convey sensory information from these muscles. Spinal and supraspinal pathways mediating excitatory and inhibitory inputs to the motor neurons are described; the relative contributions of the nerves to urethral function and their involvement in POP and incontinence are discussed. Finally, a detailed summary of the neurochemical anatomy of Onuf's nucleus and the pharmacological control of the rhabdosphincter are provided.

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.

Anorectal and pelvic floor anatomy

The anorectum and pelvic floor are crucial in maintaining continence, facilitating evacuation, providing pelvic organ support while in females the pelvic floor is part of the birth canal. The anal sphincter is a multilayered cylindrical structure, including the smooth muscle internal sphincter and the outer striated muscle layer. The latter comprises the external sphincter as lower outer half and puborectalis as upper outer half of the sphincter. The external sphincter is continuous with the rectum at the anorectal junction. The pelvic floor constitutes four principal layers: endopelvic fascia, the muscular pelvic diaphragm (commonly referred to as levator plate), the perineal membrane (urogenital diaphragm) and the superficial transverse perineii. Anorectum and pelvic floor have multiple interconnections by fascia and ligaments as well as multiple indirect connections to the bony pelvis. Other structures as perineal body and a fibro-elastic network add to this support.

Neuroanatomy of the male pelvis in respect to radical prostatectomy including three-dimensional visualization

The neuroanatomical structures of the radical prostatectomy (RP) are extensively discussed for their existence, localization and function. Especially structures, e.g. the so-called neurovascular bundle (NVB) that are points of debate in numerous anatomical studies. We review the literature and present our observations in cadaveric specimens, to reconstruct neuroanatomical structures in three dimensions (3D) with the use of appropriate computer applications and produce images of operative fields. We used an internet PubMed survey (http://www.ncbi.nlm.nih.gov) to review recent publications and included back copies of historical neuroanatomical studies from our own library. Our own experimental cadaveric (specimens preserved in Thiel's solution) studies of the autonomic nerve supply of the lower urinary tract were also reviewed. Visualization of the pelvic anatomy and neuroanatomy was done using computer-based software packages. No unified terminology for the structures of the NVBs can be presented to date. The innervation of the smooth muscular structures of the urethra and the complex morphology of urethral sphincter remain unclear. Our cadaveric studies showed that nerves are located on the lateral aspect of the prostate in addition to the NVBs described at the dorsolateral side of the prostate. The neuroanatomical investigations of the male pelvis and visualization of the structures in 3D enable the presentation of operative sites as seen intraoperatively. Moreover, dynamic depiction of the pelvic floor is also possible.

Value of frozen section biopsies during radical prostatectomy: significance of the histological results

PURPOSE

To review the evidence about frozen sections during radical prostatectomy (RP) and its ability to decrease the incidence of positive margins, the impact on PSA postoperatively and the significance of residual benign prostatic cells after prostatectomy.

METHODS

The information for this review was compiled by searching the Pubmed database. We used Mesh Terms "Prostatectomy" and "Prostatic Neoplasms" and we added "frozen sections" and/or "hyperplasic cells" and/or "benign cells" and/or "positive margins". Furthermore, we review the articles referenced in those studies and editorials letters.

RESULTS

Several groups have studied the performance of frozen section during RP to try and assess the risk of positive margins intraoperatively. The controversial sites where they should be performed are the apex, the dorsolateral zones and the bladder neck. They have been performed routinely or when the surgeon decides it, depending on the preoperative or intraoperative findings.

CONCLUSIONS

At the present time there is no standardisation in the number, the site and the type of patient where this procedure should be done. The improvement in functional outcomes and biochemical control is not proven.

Ultrasonographic anatomy of perineal structures during pregnancy and immediately following obstetric injury

OBJECTIVES

To assess perineal anatomy using ultrasound before and immediately after delivery.

METHODS

Structures in the perineum were studied by real-time two-dimensional transvaginal and endoanal ultrasound imaging using a combined linear and semicircular (up to 200 degrees sector) probe. We examined 45 nulliparous pregnant women and 44 primiparae immediately after delivery (40 with anal sphincter tears and four without sphincter injury). In each case a single longitudinal image was later assessed by two observers in order to evaluate interobserver agreement.

RESULTS

In pregnancy, the perineal membrane, puboperineal muscles, conjoined longitudinal muscle and central point were identified on real-time examination in 91%, 98%, 100% and 100% of cases, respectively. At offline evaluation of the longitudinal images obtained for each of the pregnant women, the percentage of cases in which each structure was identified by both observers ranged from 64% to 100%. In the women who were examined postpartum, all structures were identified by both observers in all four of the women without sphincter injury. In the women with sphincter tears, the perineal membrane, puboperineal muscles, conjoined longitudinal muscle and central point were found by ultrasound to be intact in 10%, 10%, 55% and 18%, respectively. The agreement between two observers regarding identification of intact structures in a single longitudinal image was good for perineal membrane (kappa index, 0.66), fair for puboperineal muscles (kappa index, 0.40), and poor for conjoined longitudinal muscle and central point (kappa index, 0.08 and 0.17, respectively).

CONCLUSIONS

Ultrasonography might be helpful in the evaluation of perineal anatomy and extent of perineal tears. However, the relatively poor agreement between the two observers evaluating single linear transvaginal images implies that both transverse and longitudinal projections are necessary to obtain relevant information. Further studies are needed regarding the importance of specific sonographically identified structures and their role in pelvic floor dysfunction after delivery.

The anatomical components of urinary continence

BACKGROUND

The levator ani muscle (LAM) plays an important role in urinary continence, but the anatomical relationship between this pelvic floor muscle and the external urethral sphincter (EUS) remains incompletely understood.

OBJECTIVE

To investigate the topographical relationship between the EUS and the LAM.

DESIGN, SETTING, AND PARTICIPANTS

Serially sectioned and histochemically stained foetal pelves from eleven females and nine males (10-27 wk of gestation) were studied. Three foetal pelves (two female, 12 and 18 wk of gestation; one male, 12 wk of gestation) and three adult pelves (two females, 54 and 85 yr; one male, 75 yr) were stained immunohistochemically for the presence of striated and smooth muscle tissue. Three-dimensional reconstructions were prepared.

MEASUREMENTS

Anatomy of the LAM and urethral sphincter components was evaluated qualitatively.

RESULTS AND LIMITATIONS

The EUS has no direct bony attachment. In female foetuses, the inferior part of the EUS is firmly attached to the LAM by a tendinous connection. Contraction of this part of the EUS produces a force on the urethra in a posteroinferior direction. Contraction of the LAM compresses the rectum and moves the rectovaginal complex anteriorly and superiorly towards the urethra in a plane that lies parallel to, but superior of, that of the EUS. Simultaneous contraction of the LAM and EUS causes an anteriorly convex bend in the midurethra, which closes the midurethral lumen. A similar attachment of the EUS to the LAM is absent in the male. Our study is limited due to the absence of young adult study specimens.

CONCLUSIONS

The EUS in females is anchored to the levator ani muscle via a tendinous connection. Because of this attachment to the LAM, proper function of the EUS is dependent on the integrity of the LAM and its attachment to the pelvic wall.

Structure of the perineal membrane in females: gross and microscopic anatomy

OBJECTIVE

To re-examine the anatomy of the perineal membrane and its anatomical relationships in whole-pelvis and histologic serial section as well as gross anatomical dissection.

METHODS

Serial trichrome-stained histologic sections of five female pelvic specimens (0-37 years old) were examined. Specimens included the urethra, perineal membrane, vagina, and surrounding structures. Macroscopic whole-pelvis sections of three adults, 28-56 years of age, in axial, sagittal, and coronal sections were also studied. Dissections of six female cadavers, 48-90 years of age, were also performed.

RESULTS

The perineal membrane is composed of two regions, one dorsal and one ventral. The dorsal portion consists of bilateral transverse fibrous sheets that attach the lateral wall of the vagina and perineal body to the ischiopubic ramus. This portion is devoid of striated muscle. The ventral portion is part of a solid three-dimensional tissue mass in which several structures are embedded. It is intimately associated with the compressor urethrae and the urethrovaginal sphincter muscle of the distal urethra with the urethra and its surrounding connective. In this region the perineal membrane is continuous with the insertion of the arcus tendineus fascia pelvis. The levator ani muscles are connected with the cranial surface of the perineal membrane. The vestibular bulb and clitoral crus are fused with the membrane's caudal surface.

CONCLUSION

The structure of the perineal membrane is a complex three-dimensional structure with two distinctly different dorsal and ventral regions; not a simple trilaminar sheet with perforating viscera.

Pelvic floor images: anatomy of the levator ani muscle

PURPOSE

The levator ani has been divided into many functional portions based on necropic observation. Our objective was to use a combination of CT and magnetic resonance images to show a complete levator ani.

METHODS

Normal magnetic resonance images of the pelvis were obtained at rest in 22 volunteers while in the lying position (10 males, aged 21-23 yr). The pelvic floor images of ten cadavers (5 males) were obtained while in the supine position by CT. Source magnetic resonance images were used to measure the heights of the transverse portion of the levator ani and the area of the genital hiatus. Source magnetic resonance images and CT reconstructed images were used to study the anatomy of the levator ani.

RESULTS

The levator ani had a transverse portion and a vertical portion. The anterior transverse portion was found to be basin-shaped, the middle transverse portion was funnel-shaped, and the posterior transverse portion was dome-shaped. The transverse portion sloped sharply downward to form the vertical portion at the puborectalis plane. The vertical portion was a muscular tube outside the intrahiatal structures. The puborectalis was a u-shaped muscle outside the vertical portion. One case of the deep transverse perineal muscle was found in 22 volunteers. The volume of the ischioanal fossa influenced the anatomic appearance of the pelvic floor in cadavers.

CONCLUSIONS

The transverse portion of the levator ani has five kinds of shapes in the different-coronal sections of the pelvis, which changes from basin to dome in a lying position. The puborectalis is outside the vertical portion and not part of the levator ani.

Disposition of the striated urethral sphincter and its relation to the prostate in human fetuses

OBJECTIVE

To describe the arrangement of the muscle fibers of the striated urethral sphincter and its relationship with the prostate during the fetal period in humans.

MATERIALS AND METHODS

We analyzed 17 prostates from well preserved fresh human fetuses ranging in age from 10 to 31 weeks postconception (WPC). Transversal sections were obtained and stained with Gomori's trichrome and immunolabeled with anti alpha-actin antibody.

RESULTS

We found that the urethral striated sphincter (rabdosphincter) is located on the periphery of the smooth muscle and there was no merge between striated and smooth muscle fibers in any fetal period. In the prostate apex, the striated sphincter shows a circular arrangement and covers completely the urethra externally, whereas adjacent to verumontanum, it looks like a "horseshoe" and covers only the anterior and lateral surfaces of the urethra. Near the bladder neck, in fetuses younger than 20 WPC, we have found striated muscle fibers only at the anterior surface of the prostate, while in fetuses older than 20 WPC, the striated muscle covers the anterior and lateral surfaces of the prostate.

CONCLUSIONS

The urethral sphincter muscle covers the anterior and lateral surfaces of the urethra in all fetuses older than 20 WPC, close to the bladder neck and at the distal prostate. In the region of the prostate apex, the urethral sphincter covers completely the urethra circularly. The knowledge of the normal anatomy of the urethral sphincter in fetuses could be important to understand its alterations in congenital anomalies involving the base of the bladder, the bladder neck and the proximal urethra.

Anatomical Landmarks of Radical Prostatecomy

INTRODUCTION

In the present study, we review current literature and based on our experience, we present the anatomical landmarks of open and laparoscopic/endoscopic radical prostatectomy.

METHODS

A thorough literature search was performed with the Medline database on the anatomy and the nomenclature of the structures surrounding the prostate gland. The correct handling of puboprostatic ligaments, external urethral sphincter, prostatic fascias and neurovascular bundle is necessary for avoiding malfunction of the urogenital system after radical prostatectomy.

RESULTS

When evaluating new prostatectomy techniques, we should always take into account both clinical and final oncological outcomes. The present review adds further knowledge to the existing "postprostatectomy anatomical hazard" debate. It emphasizes upon the role of the puboprostatic ligaments and the course of the external urethral sphincter for urinary continence. When performing an intrafascial nerve sparing prostatectomy most urologists tend to approach as close to the prostatic capsula as possible, even though there is no concurrence regarding the nomenclature of the surrounding fascias and the course of the actual neurovascular bundles. After completion of an intrafascial technique the specimen does not contain any periprostatic tissue and thus the detection of pT3a disease is not feasible. This especially becomes problematic if the tumour reaches the resection margin.

DISCUSSION

Nerve sparing open and laparoscopic radical prostatectomy should aim in maintaining sexual function, recuperating early continence after surgery, without hindering the final oncological outcome to the procedure. Despite the different approaches for radical prostatectomy the key for better results is the understanding of the anatomy of the bladder neck and the urethra.

Macroscopic and histotopographic study of the deep transverse perineal muscle (musculus transversus perinei profundus) in elderly Japanese

Although the deep transverse perineal (DTP) muscle is welt known as the core of the urogenital diaphragm, most recent studies have denied its existence. In students' dissection classes, we cut the surfaces of 93 macroscopically identified urogenital diaphragms (59 male cadavers) and found the distinct sheet-like DTP in 24.7% (23 of 93 sides). Another 17 cadavers (mean age 81.4 years) were used for histology. In histology of 12 males, we consistently identified the DTP as a small muscle bundle immediately lateral to the bulbourethral gland. Thus, the macroscopicically unclear morphology of the DTP (19.4%, 18 of 93 sides) seemed to be overestimated. The histologically proven DTP was continuous with a "tail" or inferolateral protrusion of the external urethral sphincter or urethral rhabdospincter. However, the histology revealed that a sheet-like DTP was not usual (16.7%, two of 12 cadavers). Likewise, in histology of five females, the tail always continued to a muscle mass immediately lateral to the greater vestibular gland and far dorsal to the external urethral sphincter. Thus, the female topohistology seemed to be consistent with the male unclear DTP. Because of the limited incidence of a sheet-like DTP and the unclear fascial structure containing numerous vessels around the rather small DTP, in most elderly cadavers the urogenital diaphragm was likely to be a macroscopic entity rather than a histologic one. However, we believed that the histologically proven DTP was present in elderly men and women even if it had changed as a result of degeneration with aging.

A method of dissecting the pelvic floor to allow anatomical validation of images of the soft tissues

A method of intact postmortem removal of the pelvic floor for imaging correlation studies, with minimal access disfigurement, is described. This consists of subcutaneous removal of both ischiopubic rami with division of the obturator membrane cranial to the origin of the levator ani muscles. The anatomical relationships of soft tissue surrounding the distal birth canal are thus preserved. The report discusses the need for, constraints on, and limitations of such studies in the unique problems of determining the dynamic anatomical configuration of the soft tissues of the pelvic floor. It illustrates the clinical relevance of initial studies, and reviews the background contributions of members of the group.

The urethral striated sphincter in adult male rat

This study reports the morphology of the urethral sphincter in adult male rats, mainly the histological aspects, the features of the endplates, and the heavy myosin chain distribution in the striated fibres. First, the prostate is entirely out of the striated sphincter, which is surprising when compared to man. Second, the urethral striated sphincter consists of two lateral fascicles separated by an anterior and a posterior strip of connective tissue, which extend from the prostatic urethra (i.e. the part of the urethra which runs though the prostate) to the bulb of the penis. An additional third fascicle of striated muscle (SM) covers the caudal part of the anterior connective strip of the membranous urethra (i.e. the urethra which extends from its prostatic part to the bulb of the penis). In the membranous urethra, the striated sphincter surrounds directly the urethral lumen without intercalated smooth muscle. In urethral cross sections, the endplates detected by alpha-bungarotoxin, which binds to nicotinic receptors, are clustered in the postero-lateral part of the lateral fascicles. The cross-sectional area of the urethral striated fibres shows a bimodal distribution: the largest fibres are located at the periphery of the sphincter and these fibres express only fast myosin heavy chains (MHC) as shown by immunochemistry. The smallest fibres are less numerous and are situated near the lumen co-expressing fast and slow MHC. All the striated fibres express desmin and dystrophin as SM fibres do. Taken together, these results suggest that the urethral striated fibres in male rat present the same characteristics as those of the skeletal muscles. The predominance of fast fibres is consistent with phasic contractions playing a role not only during micturition and urinary continence but also probably during ejaculation.

Striated Muscle Fiber Compositions of Human Male Urethral Rhabdosphincter and Levator Ani

PURPOSE

We clarified the contractile properties of human male periurethral striated muscle fibers to better understand how the rhabdosphincter and the levator ani maintain urinary continence.

MATERIALS AND METHODS

Muscle specimens were obtained from 52 male patients who underwent radical prostatectomy or radical cystectomy. The specimens were frozen in liquid nitrogen. Frozen sections (10 microm thick) were stained with myofibrillar ATPase at different pH values (pH 4.2, 4.6 and 10.6), and evaluated for quantitative parameters and fiber type distribution. Myosin heavy chain analysis was performed using SDS-PAGE.

RESULTS

Of all 52 cases 37 provided specimens that could be divided into the 2 major fiber types, type 1 (slow twitch) and type 2 (fast twitch). Although type 1 muscle fibers were predominant in RS and LA muscle groups (RS 69.6 +/- 2.7%, LA 67.0 +/- 2.0%), mean muscle fiber size was significantly smaller in RS (mean area 906 +/- 86 microm(2)) than in LA (mean area 2,967 +/- 170 microm(2)) (p <0.0001). In 11 specimens type 2 muscle fibers could be subdivided into types 2A (fast fatigue resistant) and 2B (fast fatigable). Type 2A fibers were significantly more prevalent than type 2B fibers (p <0.05). Likewise, MHC analysis of these 11 specimens found a significantly higher percentage of fiber type 2A expression products (MHC 2A) than of fiber type 2B expression products (MHC 2X) (p <0.05).

CONCLUSIONS

RS and LA contribute to urinary continence mechanism by slow contraction. Moreover, the smaller mean size of muscle fibers in RS suggests more fatigue resistance compared with muscle fibers in LA because small fibers have a shorter diffusion distance for metabolic substrates. These results should help contribute to a more detailed understanding of the function of periurethral striated muscles in the human male.

Histomorphology of canine urethral sphincter systems, including three-dimensional reconstruction and magnetic resonance imaging

OBJECTIVES

To present a detailed anatomic description and comparison of the smooth and striated urethral sphincter in male and female dogs. We performed a thorough histologic evaluation, three-dimensional reconstruction, and magnetic resonance imaging of the lower urinary tract of male and female dogs.

METHODS

The lower urinary tract anatomy was investigated in 16 male and 18 female dogs by serial sectioning, including immunohistochemical staining and three-dimensional reconstruction. Magnetic resonance imaging performed in 5 male and 5 female dogs before histologic investigation helped to demonstrate the anatomy in vivo.

RESULTS

A urethral sphincter muscle in both sexes existed without muscular connection to the pelvic floor. It ran circularly and consisted of an inner smooth and outer striated muscular part. In the female dog, the striated muscle encircled the urethra and vagina in the caudal third of the membranous urethra (musculus urethrovaginalis). A urinary diaphragm (diaphragma urogenitale) could not be found histologically or by magnetic resonance imaging.

CONCLUSIONS

The dog is a suitable animal model for investigations of the urethral sphincter. In the female dog, attention should be given to the special topography of the musculus urethrovaginalis.

The structure and innervation of the male urethra: histological and immunohistochemical studies with three-dimensional reconstruction

The structure of the striated urethral sphincter, the so-called rhabdosphincter, remains the subject of controversy. There are two main concepts regarding its structure: either it is a part of the urogenital diaphragm, or it extends from the base of the bladder up to the urogenital diaphragm and is an integral part of the urethra. It is also uncertain whether it possesses a somatic innervation or a mixed innervation (i.e. autonomic and somatic). The purpose of this study was to show the precise location of the nerves running to the urethra, and to try to determine their exact nature. Histology and immunohistochemistry were performed in the external urethral sphincter of ten male fetuses (114-342 mm crown-rump length, or between 14 and 40 weeks of gestation). A three-dimensional (3D) reconstruction of the urethral structure and its innervation was made from serial sections. The 3D reconstruction of the same section levels with different strains allowed us to identify the precise structure of the muscle layers (smooth and striated muscle fibres) and the nature of the nerve elements (myelinated and unmyelinated), their distributions and their relationship to the urethral wall, the prostate and the seminal vesicles. Histological and immunohistochemical 3D reconstruction of the anatomical elements of the urethral sphincter helps us to understand the 3D arrangement of the sphincter muscle layers. It also provides a better understanding of the origin and nature of the nerve elements that play a role in urinary continence.

Fetal development of striated and smooth muscle sphincters of the male urethra from a common primordium and modifications due to the development of the prostate: an anatomic and histologic study

BACKGROUND

The aim of the study was to investigate the development of the human urethral sphincter complex during fetal development.

METHODS

23 human male fetal specimens were investigated. The histological sections were processed according to the epoxy resin-based plastination technology.

RESULTS

At 9th week of gestation, a combined sphincteric primordium of the rhabdosphincter and the lissosphincter is situated at the anterior and lateral aspects of the membranous and prostatic urethra. Both muscular components assume an omega-shaped configuration due to the presence of a constant connective tissue raphe posterior to the urethra that anchors the rhabdosphincter in the perineal body. Development of the prostate laterally and posteriorly does not modify the growth of the urethral sphincter complex anteriorly but inhibits its development laterally and posteriorly.

CONCLUSIONS

The important morphological characteristics of the male adult rhabdosphincter and lissosphincter can be seen very early in fetal development.

CADAVERIC ANATOMY OF PELVIC FRACTURE URETHRAL DISTRACTION INJURY: MOST INJURIES ARE DISTAL TO THE EXTERNAL URINARY SPHINCTER

PURPOSE

The anatomy of posterior urethral distraction injuries is controversial. We present a cadaver study of posterior urethral distraction injuries. To our knowledge this is the first study that establishes that the most common location is distal to the external urinary sphincter.

MATERIALS AND METHODS

We performed an autopsy review of 10 male patients with posterior urethral distraction injuries.

RESULTS

Urethral disruption occurred distal to the external urinary sphincter in 7 of 10 patients. It appeared to occur when the anterior pelvic ring and urogenital diaphragm complex were displaced caudal and rostrally, tearing the urogenital diaphragm off of the urethra. The average inner mucosal defect +/- SD was 3.5 +/- 0.5 cm, while the defect between the outer urethral layer (tunica of the spongiosum) was 2.0 +/- 0.2 cm due to mucosal retraction. Simple and complex injuries could be observed, according to the clinical classification proposed by Turner-Warwick in 1989. Simple injuries had less significant dislocation of the symphysis, general maintenance of urethral continuity and slightly shorter mucosal distraction (3.3 cm). Complex disruptions had significant symphyseal dislocation, complete disassociation of the urethral ends (often with interposition of other tissues) and a slightly longer mucosal distraction (3.8 cm).

CONCLUSIONS

Posterior urethral distraction injuries appear to most commonly occur distal to the urogenital diaphragm, contrary to classic teaching. These injuries are on average between 3 and 4 cm, and they are more significant dorsal than ventral. They appear to occur as simple or complex injuries, mirroring the clinical findings seen in clinically simple and complex urethral strictures.

Is the rhesus monkey (Macaca mulatta) comparable to humans? Histomorphology of the sphincteric musculature of the lower urinary tract including 3D-reconstruction

The physiology of the muscle systems of the human lower urinary tract is still not known in detail. To study the functional basics of this complex organ system, experiments are often performed in animal models including rhesus monkeys. To apply the results of animal model studies to the humans, a clear knowledge of the comparative anatomy of both species is necessary. However, detailed comparative studies of the lower urinary tract of the rhesus monkey and the humans are lacking. Accordingly, a detailed study on the sphincteric musculature of the lower urinary tract of the rhesus monkey was performed in order to demonstrate anatomical correspondences and differences between both species. The lower urinary tract anatomy was investigated in 18 male and female rhesus monkeys (Macaca mulatta) by serial sections. Immunohistochemical staining methods were used to differentiate striated and smooth musculature. Three-dimensional reconstructions were performed in order to demonstrate the topographical anatomy of the different muscle systems. In both man and male rhesus monkeys, a urethral sphincter muscle exists independent of the pelvic floor musculature, with a smooth and a striated muscular part. A urinary diaphragm (diaphragma urogenitale) does neither exist in the rhesus monkey nor in the human. In contrast to women, a striated muscle encircles the urethra and vagina together in the female rhesus monkey. A vesical sphincter muscle, found in the human bladder outlet, does not exist in the rhesus monkey.

An anatomical description of the male and female urethral sphincter complex

PURPOSE

We performed a detailed study of the lower urinary tract of the male and female human fetus to elucidate the anatomy of the urethral sphincter complex in both sexes and its relationship to the surrounding organs and tissues.

MATERIALS AND METHODS

A total of 12 male and 14 female normal human pelvic specimens ranging from 17.5 to 38 weeks of gestation were studied by serial sections and immunohistochemical analysis. Three-dimensional reconstructions were created from serial sections to demonstrate the anatomy of the lower urogenital tract and urethral sphincter in both sexes. Specific attention was directed to the sphincteric muscle of the urethra.

RESULTS

The urinary continence mechanism is formed by a combination of detrusor, trigone and urethral sphincter muscles with distinctive histological characteristics in both sexes. In males the external urethral sphincter covers the ventral surface of the prostate as a crescent shape above the verumontanum, horseshoe shape below the verumontanum and crescent shape along the proximal bulbar urethra. The levator ani muscles form an open circle around the external sphincter with a hiatus at the ventral aspect. In females the external urethral sphincter covers the ventral surface of the urethra in a horseshoe shape. Caudally the same horseshoe-shaped external sphincter increases in size to envelop the distal vagina. The levator ani muscles do not support the proximal urethra. The smooth and striated muscle components of the urethral sphincter complex are inseparable in both sexes.

CONCLUSIONS

The developmental anatomy of the urethral sphincter complex is analogous in both sexes. The male and female urinary sphincter mechanism is composed of detrusor, trigone and urethral muscles, each of different muscular origins. The levator ani does not surround the ventral aspect of the urethra and may not have an active role in continence in both sexes. This new concept in the anatomy of male and female sphincter morphology may help to refine our reconstructive and ablative surgical techniques.