Current Concepts of Female Pelvic Anatomy and Physiology

Architecture of female urethral supporting structures based on undeformed high-resolution sectional anatomical images

Female urinary incontinence mainly relates to damage of female urethra supporting structures, while its anatomy and function specially in which the connective tissue part are still unclear and controversial. We study it based on 4 thin-sectional, high-resolution, transverse sectional anatomical images [Chinese Visible Human (CVH) images] and 10 high-resolution MRI images from volunteers. The female urethral supporting structures and its adjacent structures were segmented and three-dimensional (3D) reconstructed with Amira software. The urethral supporting structures include muscular and connective tissue supporting structures. Muscular supporting structures are composed of levator ani muslce and striated urethral sphincter, the connective tissue supporting structures are composed of anterior vaginal wall, pubovesical muscle, pubovesical ligament, lateral vesical ligament, and tendinous arch of pelvic fascia (TAPF). The anterior vaginal wall includes tight and loose connections between urethral, bladder, and vagina. The lateral vesical ligament connects the proximal part of the urethra to the TAPF. The pubovesical muscle is crescent shaped and continues with the detrusor of the bladder superior and directly connects the TAPF laterally. The TAPF is an obvious fibrous structure that originates at the middle-posterior surface of the pubis, travels onto the parietal pelvic fascia, and inserts posteriorly onto the ischial spine. The anterior vaginal wall, the pubovesical muscle, the lateral vesical ligament, and the TAPF create the "hammock" structure and supplement DeLancey's theory. Its support to the proximal urethra and neck of bladder is crucial to maintain stability and urinary continence during increased abdominal pressure.

Nerves and fasciae in and around the paracolpium or paravaginal tissue: an immunohistochemical study using elderly donated cadavers

The paracolpium or paravaginal tissue is surrounded by the vaginal wall, the pubocervical fascia and the rectovaginal septum (Denonvilliers' fascia). To clarify the configuration of nerves and fasciae in and around the paracolpium, we examined histological sections of 10 elderly cadavers. The paracolpium contained the distal part of the pelvic autonomic nerve plexus and its branches: the cavernous nerve, the nerves to the urethra and the nerves to the internal anal sphincter (NIAS). The NIAS ran postero-inferiorly along the superior fascia of the levator ani muscle to reach the longitudinal muscle layer of the rectum. In two nulliparous and one multiparous women, the pubocervical fascia and the rectovaginal septum were distinct and connected with the superior fascia of the levator at the tendinous arch of the pelvic fasciae. In these three cadavers, the pelvic plexus and its distal branches were distributed almost evenly in the paracolpium and sandwiched by the pubocervical and Denonvilliers' fasciae. By contrast, in five multiparous women, these nerves were divided into the anterosuperior group (bladder detrusor nerves) and the postero-inferior group (NIAS, cavernous and urethral nerves) by the well-developed venous plexus in combination with the fragmented or unclear fasciae. Although the small number of specimens was a major limitation of this study, we hypothesized that, in combination with destruction of the basic fascial architecture due to vaginal delivery and aging, the pelvic plexus is likely to change from a sheet-like configuration to several bundles.

Mechanisms of pelvic floor muscle function and the effect on the urethra during a cough

BACKGROUND

Current measurement tools have difficulty identifying the automatic physiologic processes maintaining continence, and many questions still remain about pelvic floor muscle (PFM) function during automatic events.

OBJECTIVE

To perform a feasibility study to characterise the displacement, velocity, and acceleration of the PFM and the urethra during a cough.

DESIGN, SETTING, AND PARTICIPANTS

A volunteer convenience sample of 23 continent women and 9 women with stress urinary incontinence (SUI) from the general community of San Francisco Bay Area was studied.

MEASUREMENTS

Methods included perineal ultrasound imaging, motion tracking of the urogenital structures, and digital vaginal examination. Statistical analysis used one-tailed unpaired student t tests, and Welch's correction was applied when variances were unequal.

RESULTS AND LIMITATIONS

The cough reflex activated the PFM of continent women to compress the urogenital structures towards the pubic symphysis, which was absent in women with SUI. The maximum accelerations that acted on the PFM during a cough were generally more similar than the velocities and displacements. The urethras of women with SUI were exposed to uncontrolled transverse acceleration and were displaced more than twice as far (p=0.0002), with almost twice the velocity (p=0.0015) of the urethras of continent women. Caution regarding the generalisability of this study is warranted due to the small number of women in the SUI group and the significant difference in parity between groups.

CONCLUSIONS

During a cough, normal PFM function produces timely compression of the pelvic floor and additional external support to the urethra, reducing displacement, velocity, and acceleration. In women with SUI, who have weaker urethral attachments, this shortening contraction does not occur; consequently, the urethras of women with SUI move further and faster for a longer duration.

Anatomy of the urethral supporting ligaments defined by dissection, histology, and MRI of female cadavers and MRI of healthy nulliparous women

OBJECTIVE

There has been no uniformity of opinion concerning the structures supporting the female urethra. Therefore, the aims of this prospective study were to define precisely the female urethral support structures at cadaveric anatomic dissection and histologic examination and to determine which of these structures can be detected on MRI of cadaveric specimens and of healthy volunteers.

SUBJECTS AND METHODS

Dissection of seven formalin-preserved cadavers (age at death, 25-50 years; no parity history available) was performed by a professor of anatomy to explore the anatomy of the urethral supporting ligaments and was followed by MRI of the cadaveric specimens with ligamentous markers in place and then by histologic analysis of the dissected ligaments. MRI of 17 healthy nulliparous women (age range, 20-35 years; mean age, 25.5 years) was then performed using T2-weighted, dual turbo spin-echo, balanced fast-field echo, and STIR sequences. A standardized grid system that allowed us to record structural observations on sequentially numbered axial MR images was used by a radiologist who then applied a 4-point grading scale to assess ligament visibility. Three authors--one radiologist, one anatomist, and one urologist--then compared the appearance of each ligament seen in a cadaveric specimen with its appearance on MR images of the same cadaver and on MR images of volunteers.

RESULTS

At cadaveric dissection we identified ventral and dorsal urethral ligaments. The ventral urethral ligaments included the pubourethral ligaments, which were found to consist of three separate components coursing anteroposterior from the bladder neck to the pubic bone; the periurethral ligament; and the paraurethral ligaments. Dorsal to the urethra, a slinglike ligament, which we believe should be named the "suburethral ligament," was identified. This ligament had a distinct plane of cleavage from the anterior vaginal wall. The MRI findings in the volunteers correlated with the MRI and gross anatomic findings in the cadavers. The proximal pubourethral, periurethral, paraurethral, and suburethral ligaments had visibility scores of 3 (moderately visible) or 4 (easily visible) on MRI in 47%, 65%, 47%, and 53% of volunteers, respectively.

CONCLUSION

Our results present evidence that may help resolve previous controversies regarding the MR appearance of the ventral urethral ligaments and that better define the course of the ligament dorsal to the urethra, the suburethral ligament. We hope that this detailed anatomic information about the structures involved in continence may lead eventually to improvements in the treatments for women with stress urinary incontinence.

Pelvic organ prolapse and the lower urinary tract: the relationship of vaginal prolapse to stress urinary incontinence

Vaginal prolapse and urinary incontinence frequently coexist. Rather than having a cause-and-effect relationship, these two common problems share etiologic factors. Specific tissue and functional deficiencies resulting in prolapse also are significant contributors to lower urinary tract symptoms, particularly stress urinary incontinence. This article reviews this relationship, the etiologic factors, and aspects of the clinical evaluation of the patient with prolapse and stress urinary incontinence.

Pelvic floor reconstruction: state-of-the-art and beyond

Reconstructive surgery for pelvic-floor dysfunction is challenging and complex. It requires an extensive familiarity with pelvic anatomy and a wide armamentarium of surgical procedures to offer patients with various structural defects. Not every patient is suited for every procedure and the surgeon must be able to individualize the approach. Each technique has indications and benefits: vaginal repairs are relatively simple and cause less morbidity than abdominal repairs, which are generally more durable. Laparoscopic repairs provide excellent visualization with decreased morbidity, but operative times are longer, there is greater cost, and learning curves are steep. Techniques and principles described for vaginal and abdominal approaches can be applied to laparoscopic and robotic surgery, but comparative outcomes are not available. Robotic assistance with the laparoscopic approach may bring this method to the mainstream by helping surgeons who are not trained formally in laparoscopy to perform advanced skills. Advances in technology and surgical skills will support the application of laparoscopic and robotic approaches, and the development of better synthetic and biologic materials likely will improve vaginal repairs. Future studies will determine the utility of the approach.

Anatomy of the arcus tendineus fasciae pelvis in females

Because of its proximity to the urethra, the anterior part of the arcus tendineus fasciae pelvis (ATFP) may be used in urethrosuspension procedures for urinary stress incontinence. In this study, 10 embalmed female cadaver hemipelves were dissected and their gross anatomy described. In females, the ATFP is a condensation of the endopelvic fascia. The anterior attachment of the ATFP is to the caudal inner surface of the body of the pubic bone at a site averaging 4 mm lateral to the pubic symphysis and covering an average area of 53 mm(2). Posteriorly, it attaches to the medial surface of the ischial spine. In nine of the 10 hemipelves the first anterior centimeters of the ATFP have a clear lateral fixation either to the lateral part of the levator ani muscle (n = 1), to the fascia covering the obturator internus muscle (n = 7), or to the obturator membrane (n = 1). Medially from the ATFP derives a 2-3-cm long flat fibrous attachment to the posterolateral aspect of the urethra. In eight unembalmed cadavers, the ATFP gave way at a pulling force of 8.2 kg (range = 3.5-11.5 kg). The ATFP resists caudal movement of the proximal anterior vaginal wall and the urethra in the upright posture and, therefore, may be suitable for urethrosuspension procedures.

Dynamic MR imaging of female organ prolapse

MR imaging is a viable technique for evaluating pelvic organ prolapse. Dynamic imaging with adequate increase in abdominal pressure is necessary for a successful study. Rectal contrast for patient defecation is easy to administer and also allows for the diagnosis of rectal abnormalities. Additional work is needed on the soft tissue changes of prolapse and grading criteria for MR.

Retropubic surgery for stress urinary incontinence

More than 150 surgical techniques have been proposed in the literature for treating stress urinary incontinence. Many of the original published approaches were vaginal, but through the years the literature has expanded to include needle suspension, pubovaginal slings, and retropubic procedures. In this chapter, we focus on retropubic approaches for the treatment of SUI and discuss the physiology, indications, technical details and the complications of these procedures.

Stress incontinence observed with real time sonography and dynamic fastscan magnetic resonance imaging--insights into pathophysiology

Our concepts of pathophysiology of stress urinary continence have been greatly shaped by developments in radiographic imaging. Simple radiographs with and without contrast initially revealed the importance of urethral descent in pathogenesis. More recently, magnetic resonance imaging (MRI) and real time ultrasonography are showing soft tissue detail within both a global pelvic and a local urethral context. Careful examination of these studies can extend our concepts of pathophysiology and lead us beyond existing paradigms. We propose a unified theory of stress incontinence based on our dynamic fastscan MRI and real time ultrasonograms of stress incontinence, incorporating known details of pelvic anatomy, sphincteric location and function. The hypothesis introduces the concept of a continence threshold at which the urethra is subjected simultaneously to both shearing and explusive forces. If these forces are sufficient to overcome urethral coaptation at threshold, leakage results. The model proposes an anatomical sequence of changes through which the incontinent urethra cycles between periods of rest and increased abdominal pressure, and suggests a way in which repeated episodes of prolpase and urethral traction by shearing forces exerted by the vagina on the urethra may contribute to the development of intrinsic sphincteric deficiency.

Pelvic floor imaging

A greater awareness of the therapies now available for pelvic floor dysfunction has increased demand for specialized imaging of this region. Some of the techniques required are available at relatively few centers, and the purpose of this review is to introduce the emerging subspecialty of pelvic floor imaging to a more general readership. Pelvic floor anatomy is complex and is being unraveled by means of magnetic resonance (MR) imaging. This is discussed in detail by using a global, rather than a compartmentalized, anatomic approach. The physiology of normal urinary and anal function and the routine clinical tests applied to them are outlined. The imaging techniques involved include MR imaging, endosonography, and fluoroscopy. The main investigations include video urodynamic imaging, evacuation proctography, dynamic cystoproctography, dynamic MR imaging of the pelvic floor, and endoluminal imaging of the anal sphincters with MR imaging and ultrasonography. These are described in detail, and their role with regard to the main pathologic conditions of the pelvic floor--urinary and anal incontinence, constipation, and prolapse--are discussed.

Dynamic MR imaging of pelvic organ prolapse: spectrum of abnormalities

Pelvic organ prolapse is a relatively common condition in women that can have a significant impact on quality of life. Pelvic organ prolapse typically demonstrates multiple abnormalities and may involve the urethra, bladder, vaginal vault, rectum, and small bowel. Patients may present with pain, pressure, urinary and fecal incontinence, constipation, urinary retention, and defecatory dysfunction. Diagnosis is made primarily on the basis of findings at physical pelvic examination. Imaging is useful in patients in whom findings at physical examination are equivocal. Fluoroscopy, ultrasonography, and magnetic resonance (MR) imaging can be useful in evaluating pelvic organ prolapse. Advantages of MR imaging include lack of ionizing radiation, depiction of the soft tissues of the pelvic floor, and multiplanar imaging capability. Dynamic imaging is usually necessary to demonstrate pelvic organ prolapse, which may be obvious only when abdominal pressure is increased. Treatment is more likely to be successful if a survey of the entire pelvis is performed prior to therapy. Therapy is usually undertaken only in symptomatic patients. In all patients, imaging findings must be interpreted in conjunction with physical examination findings and the patient's symptoms.

Effect of simulated birth trauma on the urinary continence mechanism in the rat

OBJECTIVES

To examine the effect of simulated birth injury in an animal model as part of a study on the pathogenesis of stress urinary incontinence (SUI) and the urinary continence mechanism.

METHODS

A balloon was inflated in the vaginas of rats for 4 hours to simulate prolonged labor. The effect on the continence mechanism was assessed by functional, anatomic, biochemical, and histologic examinations. The functional test consisted of placing chili powder or a clipped whisker into the rat's nostrils to induce sneezing. Anatomic measurement of the genital hiatus was performed with a caliper. Serum creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) were measured to examine the value of muscle injury in predicting incontinence. c-Fos immunostaining in the spinal cord was used as a marker of nerve injury. These data were then correlated with histopathologic examination of the urethra and pelvic floor tissues.

RESULTS

Four weeks after simulated birth injury, SUI was noted in 19 of 48 experimental rats. The genital hiatus was significantly wider in incontinent rats. The serum CPK and LDH levels were markedly elevated, but no difference was noted between the continent and incontinent rats. All experimental rats showed many c-Fos immunostaining neurons in the L6 to S1 spinal cord segments, but none was seen in control rats. Histologic study revealed a marked decrease of ganglion cells in the neural plexuses posterolateral to the vagina in experimental rats. After 4 weeks, muscle necrosis and degeneration, irregular shape and size of muscle fibers, and a change in the type I/II ratio were prominent features in the levator ani. In the urethra, we noted a significant decline in urethral wall musculature (both smooth and striated) in incontinent rats.

CONCLUSIONS

In this novel rat model, simulated birth injury resulted in SUI in a portion of the animals. Pathologic changes in the urethra, pelvic ganglia, and levator muscles seem to be the contributing factors to SUI.

Magnetic resonance imaging of the female pelvic floor and urethra: body coil versus endovaginal coil

The anatomy of the female pelvic floor and urethra is complex. With the introduction of MRI, the discussion about the normal anatomy of this area has not diminished. The use of a body coil may be contributary to this. In the present study images obtained with an endovaginal coil are compared with those of a quadrature body coil series to study the possible advantage of endovaginal imaging. Axial and radial T2-w TSE images at a 1.0-T machine were obtained in seven healthy volunteers. The pelvic floor structures as well as the levator ani muscle and the urogenital diaphragm are excellently demonstrated with the endovaginal coil. Also, the urethrovaginal sphincter could be recognized in six volunteers, but only in three with the body coil. In six volunteers a new ligamentous structure, the urethropelvic sling, connecting the urethra to the levator ani muscle and contributing to the supporting mechanism of the urethra is shown with the endovaginal coil. The zonal anatomy of the urethra is excellently shown with the endovaginal coil. The urethral length could only be accurately measured with this coil and ranged from 3.1 to 3.6 cm. Compared with the body coil, endovaginal MRI is excellent in demonstrating the anatomy of the pelvic floor and urethra.

Anatomic goals in the correction of female stress urinary incontinence

The goal of stress incontinence surgery is to prevent opening of the urethra during increases in intra-abdominal pressure. Greater refinements in the understanding of the pathophysiology of incontinence and experience with newer treatments have extended surgical thinking beyond the familiar paradigm "to place the urethra in a high retropubic position." When incontinence is associated with vaginal hypermobility, vaginal support may be sufficient to restore continence if the suburethral vaginal wall is sufficiently strong, an evaluation which must often be made by physical examination alone. However, when the vaginal wall is weak, the urethra will require an alternative form of support, usually a sling. If the urethra is intrinsically deficient, vaginal support may not be sufficient to prevent opening during increased intra-abdominal pressure, and coaptation by sling obstruction or periurethral bulking injection may be required. Most laparoscopic approaches to stress incontinence use Burch's method, which offers excellent urethral stability provided the suburethral vaginal wall is strong. Newer insights into the relation between vaginal mobility and urethral closure are discussed, as well as anatomic aspects of the Burch suspension relevant to laparoscopic repair.

Functional anatomy of the organs of micturition

The anatomy of the organs of micturition has been the subject of study for nearly 150 years. As a result of advances in techniques and methods of clinical and research investigation, studies over the past three decades have intensified and have been increasingly directed at the functional implications and significance of organ anatomy and structure. This has led to revision of many traditional ideas about micturition and the development of new viewpoints and modalities for study of its disorders. This article summarizes the evolution of our thinking and understanding of the functional anatomy of the bladder and urethra over the years, and suggests possible directions for continued clinical study and investigation.

Urethral sphincter volumes in women with obstructed voiding and abnormal sphincter electromyographic activity

OBJECTIVE

To investigate the role of transrectal ultrasonography (TRUS) of the female urethral sphincter and to compare sphincter volumes in controls and women with obstructed voiding associated with abnormal myotonic-like electromyographic (EMG) activity in the urethral sphincter.

PATIENTS AND METHODS

Fourteen women patients (mean age 29 +/- 3.2 years) with symptoms of urinary outlet obstruction underwent videocystometrography (VCMG), urethral sphincter EMG and TRUS. Their sphincter volumes were compared with those obtained from 20 age-matched control patients with other urodynamic diagnoses or normal urodynamics.

RESULTS

In every patient the urethral sphincter was identified as an ovoid, hypoechoic structure distal to the bladder outlet. The mean volume of the sphincter in those patients with abnormal EMG activity (3.05 +/- 0.23 cm3) was significantly greater than that in the control group (1.30 +/- 0.09 cm3; P < 0.001).

CONCLUSION

TRUS provided a useful method of imaging the urethral sphincter in women. The results suggest that there was an increase in the volume of the urethral sphincter in females with obstructed voiding, providing collateral evidence that the abnormal EMG activity is a significant factor in the pathophysiology of the disorder.

Surgical Procedure for Treatment of Urinary Stress Incontinence

Genuine Stress Incontinence (GSI) is one of the most important chapters of female urology. Surgical treatment of GSI still remains an area of controversy in urology. The authors give an up-dated review of the subject; valuable support for people involved in this field.