IN SITU ANATOMICAL STUDY OF THE MALE URETHRAL SPHINCTERIC COMPLEX: RELEVANCE TO CONTINENCE PRESERVATION FOLLOWING MAJOR PELVIC SURGERY

Purpose

We describe a correlative gross anatomical and histological study of the human male urethral sphincteric complex using methods that delineate skeletal, muscular and fascial components.

Materials and Methods

Pelves of 6 fresh frozen male cadavers were sectioned as 4 mm. tissue blocks in planes sagittal and perpendicular to the axis of the prostatomembranous urethra from the bladder neck to the bulb of the corpus spongiosum. Sections were photographed and prepared in situ for histological staining (hematoxylin and eosin, Masson's trichrome and phosphotungstic acid hematoxylin).

Results

The structure of the male urethral sphincteric complex was demonstrated to include the cylindrical rhabdosphincter surrounding the prostatomembranous urethra and a fascial framework, principally consisting of the ventral subpubic fascia and medial fascia of the levator ani musculature. The histological appearance of the rhabdosphincter at its dorsal aspect suggested a suburethral musculofascial plate. Rhabdosphincteric muscle fibers were oriented in vertical and ventrolateral directions with attachments to the subpubic fascia and the medial fascia of the levator ani.

Conclusions

The structural components and their relationships suggest mechanisms whereby the complex is suspended and stabilized within the deep pelvis, and achieves urethral closure. Our study furthers an understanding of the anatomical basis for male urinary continence and micturition, and is expected to have primary importance in the effort to preserve urinary function following major pelvic surgery.     

Normal anatomy of urethral sphincter complex in young Chinese males on MRI

Purpose

In this research, the normal anatomy of urethral sphincter complex in young Chinese males has been studied.

Methods

The sagittal, coronal, and axial T2-weighted non-fat suppressed fast spin-echo images of pelvic cavities of 86 Chinese young males were studied.

Result

Urethral sphincter complex is a cylindrical structure surrounding the urethra and extending vertically from bladder neck to perineal membrane. Urethral striated sphincter covers the anteriolateral urethra like a hat from bladder neck to verumontanum, while it surrounds the urethra in a ring shape from verumontanum to perineal membrane and backwards ends in central tendon of the perineum. From bladder neck to perineal membrane, the thickness of urethral smooth sphincter decreases gradually, and it extends forward to surround urethra with urethral striated sphincter as a ring. The length of urethral striated sphincter is 12.26–20.94 mm (mean 16.59 mm) at membranous urethra: 27.88–30.69 mm (mean 28.99 mm) from verumontanum to perineal membrane. The thickness of striated sphincter at membranous urethra is 4.29–6.86 mm (mean 5.56 mm) for the muscle of the anterior wall and 2.18–2.34 mm (mean 2.26 mm) for the muscle of the posterior wall.

Conclusions

In this paper, we summarized the normal anatomy of urethral sphincter complex in young Chinese males with no urinary control problems.     

Pressure-to-Cross-Sectional Area Relationships in the Proximal Urethra of Men with Bladder Outlet Obstruction

Purpose

Related values of pressure and cross-sectional area in the proximal urethra were measured in patients with bladder outlet obstruction. Urethral opening pressure and elastance (the inverse of compliance) were estimated.

Materials and Methods

We studied 15 men with standard urodynamic examinations. The pressure-to-cross-sectional area relationship in the prostatic urethra was determined using a special probe.

Results

Elastance varied significantly along the studied portion of the urethra, with higher values found in the sphincter area. The estimated urethral opening pressure appeared high compared to that in unobstructed cases and without variation along the prostatic urethra.

Conclusions

The most important effect of prostatic obstruction appears to be the increased urethral opening pressure.     

Risk of Urethral, Vaginal and Cervical Involvement in Patients Undergoing Radical Cystectomy for Bladder Cancer: Results of a Contemporary Cystectomy Series from M. D. Anderson Cancer Center

Purpose

Orthotopic bladder reconstruction in women is the focus of considerable interest. To define suitable candidates for orthotopic reconstruction among women with bladder cancer, we reviewed the risk of secondary urethral, vaginal and cervical involvement by transitional cell carcinoma in patients who underwent radical cystectomy at our institution.

Materials and Methods

We retrospectively reviewed the charts of women who underwent radical cystectomy for primary transitional cell carcinoma of the bladder between 1985 and 1995. These cases also were reviewed pathologically.

Results

Of 115 patients who underwent radical cystectomy for transitional cell carcinoma of the bladder 9 (8%) also had secondary transitional cell carcinoma cell of the urethra, including 2 with concomitant involvement of the vagina or cervix. In 4 patients (3%) the vagina or cervix was involved but not the urethra. Vaginal and cervical invasion correlated with stages T3b and T4 disease (p = 0.04). By logistic regression analysis the sole significant risk factor for urethral involvement was bladder neck involvement (p = 0.0005). Unlike previous studies 2 of 9 patients with secondary urethral transitional cell carcinoma did not have apparent cancer at the bladder neck.

Conclusions

We report secondary urethral involvement without apparent bladder neck involvement in women with transitional cell carcinoma. Women who are candidates for orthotopic reconstruction should undergo biopsies of the bladder neck and urethra as part of the preoperative evaluation. In patients with palpable masses (stage T3b) on bimanual examination, transvaginal biopsies should also be considered. Intraoperative frozen sections of the urethral and vaginal margins should be obtained.     

Fetal development of the female external urinary sphincter complex: an anatomical and histological study

PURPOSE: We investigated the fetal development of the smooth (lissosphincter) and striated (rhabdosphincter) female external urinary sphincter. Growth and organization of the muscle fibers around the urethra and morphological modifications due to the development of the vagina were analyzed in detail. MATERIALS AND METHODS: A total of 28 human female fetal specimens were investigated in an anatomical and histological study. The sections were processed according to plastination technology. This technique allows examination of structures and organs of the small pelvis with minimal artifacts in all 3 planes. RESULTS: At gestational week 9 the primordium of the external urethral sphincter complex was observed extending along the anterior aspect of the urogenital sinus, before the development of the primitive urethra and the vaginal primordium. From 15 weeks of gestation the lissosphincter and rhabdosphincter could be identified and clearly distinguished. After 20 weeks of gestation both elements acquired an omega-shaped configuration with a narrow posterior connective tissue raphe that was constantly present, fixing both components to the ventral vaginal wall. Both muscles were mainly located in the middle third of the urethra. In the proximal third of the urethra growth of the vagina led to disappearance of the striated muscle fibers of the rhabdosphincter, whereas the lissosphincter seemed to intermingle with the internal layer of the detrusor musculature of the bladder. CONCLUSIONS: The important morphological characteristics of the female adult rhabdosphincter and lissosphincter (omega-shaped configuration, presence of a narrow connective tissue raphe posteriorly and maximum thickness in the middle third of the urethra) are already evident early in fetal development and do not evolve during postnatal growth or by the influence of sex hormones.     

Neural supply of the male urethral sphincter: comprehensive anatomical review and implications for continence recovery after radical prostatectomy

Purpose

To review the anatomical facts of urethral sphincter (US) innervation discovered over the last three decades and to determine the implications for continence recovery after radical prostatectomy (RP).

Methods

Using the PubMed^® database, we searched for peer-reviewed articles in English between January 1985 and September 2015, with the following terms: ‘urethral sphincter,’ ‘urethral rhabdosphincter,’ ‘urinary continence and nerve supply’ and ‘neuroanatomy and nerve sparing.’ The anatomical methodology, number of bodies examined, data, figures, relevant facts and text were analyzed.

Results

Seventeen articles on 254 anatomical subjects were reviewed. Coexisting pathways were described in every article. Dissection, histology, simulation or electron microscopy evidence supported arguments for somatic and autonomic pathways. From the most to the least substantiated, somatic sphincteric fibers were described extra- or intrapelvic as: direct from the distal pudendal nerve (PuN), recurrent from the dorsal nerve of the penis, from the proximal PuN with an intrapelvic course, extrapudendal somatic fibers dispersed among autonomic pelvic fibers. From the pelvic plexus, or from the neurovascular bundles, autonomic fibers to the US have been described in 13 of the reviewed articles, with at least each of the available anatomical methods.

Conclusion

Because continence depends on a number of factors, it is challenging to delineate the specific impact of periprostatic nerve sparing on continence, but the anatomical data suggest that RP surgeons should steer toward the preservation and protection of these nerves whenever possible.

     

Anatomy and innervation of the rhabdosphincter of the male urethra

The striated sphincter of the male urethra and its innervation are still a subject of controversy. Essentially, two concepts of its anatomy can be found in the literature. Some authors describe the rhabdosphincter as part of the urogenital diaphragm caudal to the prostate, others as a striated muscle which extends from the base of the bladder to the “urogenital diaphragm.” In a combined anatomic-histologic study the striated sphincter and the pudendal nerve were examined by means of anatomical dissections and serial anatomical as well as histological sections of 12 male pelves. Furthermore, radical prostatectomy was performed in a cadaver specimen; subsequently, the so-called “urogenital diaphragm” was excised and then examined histologically. The varying number of striated muscle fibers caudal to the prostate is of particular interest. In fetuses, there are abundant striated muscle fibers dorsal to the membranous urethra, where they are arranged as a circular collar around the urethra. In the adult male, hardly any striated muscle fibers can be found dorsal to the urethra; in a majority of cases this region is devoid of striated muscle fibers. Inserting dorsally in the perineal body, the fibers form an omega-shaped loop around the anterior and lateral aspects of the membranous urethra. The existence of a “urogenital diaphragm” and a strong, circular, striated “external sphincter urethrae” completely encircling the urethra caudal to the apex of the prostate could not be confirmed by our anatomical and histological investigations. Our study shows that the striated muscle fibers run in a cranial direction from the bulb of the penis to the base of the bladder along the anterior and lateral aspects of the prostate and the membranous urethra. Further dissection studies revealed that the rhabdosphincter is supplied by branches of the pudendal nerve after leaving the pudendal canal. © 1996 Wiley-Liss, Inc.     

Anatomical approach for surgery of the male posterior urethra

OBJECTIVE

To investigate, in a morphological study, the anatomy of the male rhabdosphincter and the relation between the membranous urethra, the rhabdosphincter and the neurovascular bundles (NVBs) to provide the anatomical basis for surgical approach of the posterior urethra as successful outcomes in urethral reconstructive surgery still remain a challenging issue.

MATERIALS AND METHODS

In all, 11 complete pelves and four tissue blocks of prostate, rectum, membranous urethra and the rhabdosphincter were studied. Besides anatomical preparations, the posterior urethra and their relationship were studied by means of serial histological sections.

RESULTS

In the histological cross‐sections, the rhabdosphincter forms an omega‐shaped loop around the anterior and lateral aspects of the membranous urethra. Ventrally and laterally, it is separated from the membranous urethra by a delicate sheath of connective tissue. Through a midline approach displacing the nerves and vessels laterally, injuries to the NVBs can be avoided. With meticulous dissection of the delicate ventral connective tissue sheath between the ventral wall of the membranous urethra and the rhabdosphincter, the two structures can be separated without damage to either of them. This anatomical approach can be used for dissection of the anterior urethral wall in urethral surgery.

CONCLUSIONS

Based on precise anatomical knowledge, the ventral wall of the posterior urethra can be dissected and exposed without injuring the rhabdosphincter and the NVBs. This approach provides the basis for sparing of the rhabdosphincter and for successful outcomes in urethral surgery for the treatment of bulbo‐membranous urethral strictures.     

Urodynamic Assessment of Urethral Sphincter Function In Post-Prostatectomy Incontinence

Purpose

Direct measurement of maximum urethral pressure by urethral profilometry has been used widely to assess urethral sphincter function. We attempted to determine if there was any relationship between maximum urethral pressure, which is measured at the level of the membranous urethra, or extrinsic urethral sphincter function, and the amount of abdominal pressure needed to cause leakage (abdominal leak point pressure) in men with post-prostatectomy incontinence. We also examined the relationship between external sphincter function and continence or incontinence.

Materials and Methods

We retrospectively evaluated fluoro-urodynamics performed in 37 men with post-prostatectomy incontinence. Urodynamic study consisted of measurement of maximum urethral and abdominal leak point pressures, and assessment of extrinsic sphincter function by pressure measurements and radiographically.

Results

Data were analyzed on 27 patients for whom abdominal leak point and maximum urethral pressures were available. Mean maximum urethral pressure was 52.5 cm. water (range 20 to 165) and mean abdominal leak point pressure was 77.8 cm. water (range 27 to 132). Regression analysis was performed between maximum urethral and abdominal leak point pressures. A Pearson correlation coefficient of 0.13834 was calculated (p = 0.4914) indicating virtually no correlation between the 2 measurements in our sample. Extrinsic urethral sphincter was normal in all patients. Only 1 of 37 patients had no evidence of intrinsic sphincter deficiency, that is there was no urine leakage with increases in abdominal pressure and the patient was incontinent solely based on bladder dysfunction (detrusor instability).

Conclusions

Our study indicates that incontinence after prostatectomy due to an increase in abdominal pressure (stress incontinence) does not depend on extrinsic sphincter function and is not related to maximal urethral pressure. We conclude that post-prostatectomy incontinence due to sphincter dysfunction results from intrinsic sphincter deficiency. In our experience bladder dysfunction is rarely the sole cause of post-prostatectomy incontinence.     

PRESERVATION OF THE ANTERIOR URETHRAL LIGAMENTOUS ATTACHMENTS IN MAINTAINING POST-PROSTATECTOMY URINARY CONTINENCE: A COMPARATIVE STUDY

Purpose

The impact was determined on post-prostatectomy urinary incontinence of a technique preserving the anterior attachments of the proximal urethra to the posterior pubis by comparison to the results of other surgical methods.

Materials and Methods

Urinary continence in 51 patients undergoing preservation of the anterior urethral attachments was compared to that of 70 patients undergoing an anatomical prostatectomy with resection of the bladder neck, 55 patients with preservation of the bladder neck and 14 patients undergoing a dorsal vein gathering procedure. Comparisons were made for rate of total continence, time to return of continence, incidence of extra organ disease and operative blood loss.

Results

Total continence at 1 year was 84.3%, 85.7% and 100% respectively. Immediate total continence after catheter removal was seen in 25.5% after preservation of the anterior urethral attachments, 80.4% at 3 months compared to 41.4%, 50.9% and 50% at 3 months for anatomical prostatectomy with bladder neck resection, preservation and dorsal vein gathering. Clinical staging with the incidence of specimen confined disease was similar in all groups. Mean operative blood loss was 1,031 ml. for those patients undergoing anatomical prostatectomy compared to 681 ml. for those with preservation of the anterior urethral attachments.

Conclusions

Preservation of the anterior urethral attachments results in improved urinary continence and lower operative blood loss without an increase in positive surgical margins.     

Preservation of the smooth muscular internal (vesical) sphincter and of the proximal urethra during retropubic radical prostatectomy: Description of the technique

We describe our technique for preservation of the smooth muscular internal (vesical) sphincter and proximal urethra during radical retropubic prostatectomy. The first steps of the prostatectomy reflect the standard retropubic prostatectomy; whereas for the final phases, the procedure continues in an anterograde manner with incision of the fibers of the detrusor muscle at the insertion of the ventral surface of the base of the prostate. At this level, the inner circular muscle of the bladder neck forms a sphincteric ring of smooth muscle that covers the longitudinally‐oriented smooth muscle component of the urethra that extends distally to the verumontanum; these two proximal structures represent the internal sphincter that envelops and locks the proximal urethra. A blunt dissection is continued until the ring‐shaped vesical sphincter is separated from the prostate and the longitudinally‐oriented smooth muscle component of the urethral musculature is identified. The base of the prostate is then gently separated from the urethra and from the bladder until the maximal length of the urethral musculature is isolated and preserved. Finally, a urethra‐urethral anastomosis is carried out and the ventral stitches are placed through the circular fibres of the bladder neck. In all cases we carry out circumferential biopsies of the proximal urethra and of the base of the prostate. The described technique is a feasible and safe method for preservation of the internal urethral sphincter. Despite the enthusiasm regarding our positive functional results, further studies with larger series are required to confirm these findings.     

Reconstruction of Membranous Urethral Strictures

Purpose of Review

Due to the proximity of the rhabdosphincter and cavernous nerves to the membranous urethra, reconstruction of membranous urethral stricture implies a risk of urinary incontinence and erectile dysfunction. To avoid these complications, endoscopic management of membranous urethral strictures is traditionally favored, and bulboprostatic anastomosis is reserved as the main classical approach for open reconstruction of recalcitrant membranous urethral stricture. The preference for the anastomotic urethroplasty among reconstructive urologists is likely influenced by the familiarity and experience with trauma-related injuries. We review the literature focusing on the anatomy of membranous urethra and on the evolution of treatments for membranous urethral strictures.

Recent Findings

Non-traumatic strictures affecting bulbomembranous urethra are typically sequelae of instrumentation, transurethral resection of the prostate, prostate cancer treatment, and pelvic irradiation. Being a different entity from trauma-related injuries where urethra is not in continuity, a new understanding of membranous urethral anatomy is necessary for the development of novel reconstruction techniques. Although efficacious and durable to achieve urethral patency, classical bulboprostatic anastomosis carries a risk of de-novo incontinence and impotence. Newer and relatively less invasive reconstructive alternatives include bulbar vessel-sparing intra-sphincteric bulboprostatic anastomosis and buccal mucosa graft augmented membranous urethroplasty techniques. The accumulated experience with these techniques is relatively scarce, but several published series present promising results. These approaches are especially indicated in patients with previous transurethral resection of the prostate in which sparing of rhabdosphincter and the cavernous nerves is important in attempt to preserve continence and potency. Additionally, introduction of buccal mucosa onlay grafts could be especially beneficial in radiation-induced strictures to avoid transection of the sphincter in continent patients, and to preserve the blood supply to the urethra for incontinent patients who will require artificial urinary sphincter placement. The evidence regarding erectile functional outcomes is less solid and this item should be furtherly investigated.

     

Age dependent apoptosis and loss of rhabdosphincter cells

PURPOSE: To our knowledge the exact age dependent morphological and functional changes of the sphincter mechanism have not been investigated. Therefore, cell densities of the urethra and the urethral rhabdosphincter across various age groups, and the appearance of apoptosis were examined to explore the changes in these structures during the aging process. MATERIALS AND METHODS: Specimens were obtained from 16 male and 7 female cadavers 5 weeks to 92 years old. Histological sections were taken from 3 different levels of the rhabdosphincter and urethra. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling method was used to detect apoptosis in the urethra and rhabdosphincter. In all specimens relative volume densities of the striated muscle fibers, apoptotic indexes and diameters of the rhabdosphincter and urethra were determined. RESULTS: An age dependent increase of apoptosis of the striated muscle fibers of the rhabdosphincter led to a dramatic decrease in the number of striated muscle cells. In the 5-week-old neonate 87.6% and in the 91-year-old woman 34.2% of the rhabdosphincter consisted of striated muscle cells. Overall, a direct linear correlation between the age of the specimens and decrease in volume densities of the striated muscle cells was evident. CONCLUSIONS: The dramatic decrease in the number of striated muscle cells in the rhabdosphincter of the elderly due to apoptosis represents the morphological basis for the high incidence of stress incontinence in this population.     

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.     

Urodynamic Analysis of Age-Related Changes of alpha sub 1 -Adrenoceptor Responsiveness in Female Beagle Dogs

Purpose

We have evaluated age-related changes of alpha₁-adrenoceptor responsiveness in the lower urinary tract of female beagle dogs by urodynamic analyses.

Materials and Methods

Six aged parous and 6 young nonparous female beagle dogs were studied. Mean ages (plus/minus standard error of the mean) of the 2 groups were 68.3 plus/minus 2.3 and 12.4 plus/minus 0.08 months. Before and after 4 administrations of alpha₁-adrenoceptor agonist (midodrine hydrochloride 0.03, 0.1, 0.3 and 1.0 mg./kg. intravenously), cystometry, urethral pressure profilometry and external urethral sphincter electromyography were performed.

Results

After 0.3 mg./kg. midodrine administration, mean bladder capacity in the aged dogs significantly decreased, compared with that in the young dogs (p less than 0.05). After the minimum dose administration (0.03 mg./kg.), the urethral closing pressure in both groups increased significantly (p less than 0.05) with no changes in bladder capacity or arterial blood pressure. The proximal urethral closing pressure in the aged dogs increased dose dependently. After administration of 1.0 mg./kg. drug it reached 257 percent of the initial values (p less than 0.01), which was significantly greater than that in the young dogs (p less than 0.05).

Conclusions

These findings suggest that 1) age-related increase of alpha₁-adrenoceptor responsiveness occurs in the bladder and in the proximal urethra. The former may be one of the etiologies of detrusor instability in the elderly. 2) A lower dose of midodrine hydrochloride may be useful for the treatment of stress incontinence, independent of age.     

ABOLITION OF CYSTITIS-INDUCED BLADDER INSTABILITY BY LOCAL SPINAL CORD COOLING

Purpose

The efficacy of lumbosacral spinal cord cooling for the suppression of reflex urinary incontinence was evaluated in a rat model of cystitis-induced bladder instability.

Materials and Methods

In female Sprague-Dawley rats, overactivity of the detrusor muscle was induced by inflammation of the urinary bladder. Isovolumetric intravesical pressure, urethral perfusion pressure and electromyographic (EMG) activity of the external urethral sphincter (EUS) were recorded simultaneously during repetitive local cooling (-2C or +15C) and rewarming (to 37C) of the dorsal L6/S1 spinal cord segments.

Results

Mustard oil-induced inflammation led to a marked instability of the urinary bladder without affecting urethral outlet functions. Local cooling of the dorsal lumbosacral spinal cord with temperatures of −2C as well as +15C completely abolished bladder voiding contractions in rats with an inflamed bladder as well as in non-inflamed control animals. Cooling had little effect on the EMG activity of the EUS and increased the urethral perfusion pressure. The suppression of detrusor reflex contractions was reversed within 1-7 min. after rewarming of the spinal cord.

Conclusions

Cooling of the dorsal spinal cord at the origin of the parasympathetic innervation of the bladder can be used for a reversible suppression of bladder instability without affecting the urethral outlet. Thus, local spinal cord cooling may offer a suitable method to restore continence in cases of reflex incontinence.     

Topographical relationship between urethral rhabdosphincter and rectourethralis muscle: A better understanding of the apical dissection and the posterior stitches in radical prostatectomy

Objectives:   To clarify the topographical relationship between the urethral rhabdosphincter and the rectourethralis muscle as these structures lying dorsally to membranous urethra are important factors to post-prostatectomy urinary continence.
Methods:   Pelvic floor specimens including prostate, bulbus penis, and anorectum, obtained from 15 male cadavers (ages at death 66 to 80 years), were examined with standard histologic and immunohistochemical techniques using semiserial sagittal and transverse sections.
Results:   The rectourethralis muscle was defined. It was found to be located at the interface between the levator ani muscle and rectum. It was not possible to histologically identify the fibromuscular node known as the perineal body. The urethral rhabdosphincter was found to be inserted into the rectourethralis muscle, which is composed of the smooth muscle fibers. Abundant nerves passed between the rectourethralis muscle and the levator ani, or through the rectourethralis muscle. The urethral rhabdosphincter was closely attached to the apical or ventral portion of the rectourethralis muscle. Morphologically, the membranous urethra was fixed to the rectourethralis muscle through the urethral rhabdosphincter.
Conclusions:   The rectourethralis muscle influences the stabilization of membranous urethra. The posterior stitches for the reconstruction of the dorsal musculofascial plate might injure the nerve fibers running along and through the rectourethralis muscle.     

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.     

A Balloon-Tipped Catheter for Measuring Urethral Pressures

Background:

Better methods are needed for recording urethral function for complex urologic problems involving the bladder, urethra, and pelvic floor.

Objective:

To evaluate a balloon catheter for recording urethral pressure and function using bench-top testing and evaluation in an animal model.

Methods:

Balloon pressure–recording methods included slightly inflating the balloon with water and placing the pressure transducer on the distal end of the catheter. For bench-top testing, manual procedures and a silastic tube with a restriction were used. In 3 anesthetized dogs, pressure recorded from the skeletal urethral sphincter was induced with electrical stimulation of the sphincter. Anal sphincter pressure was also recorded.

Results:

Bench-top testing showed good pressure recordings, including a confined peak at the tube restriction. Animal tests showed urethral pressure records with rapid responses when electrical stimulation was applied. Peak pressure at the urethral skeletal sphincter was 55.7 ± 15 cmH₂O, which was significantly higher than the peak pressure recorded 2 cm distally in the proximal urethra (3.3 ± 2.3 cmH₂O). Peak anal pressures were smaller and unchanged for the 2 stimulations.

Conclusions:

Balloon-pressure recordings showed rapid responses that were adequate for the tests conducted. In the animal model, high-pressure contractions specific to the skeletal urethral sphincter were shown. Balloon-tipped catheters warrant further investigation and may have applications for the evaluation of detrusor-sphincter dyssynergia after spinal cord injury or for stress urinary incontinence.     

Safer urethral catheters: how study of catheter balloon pressure and force can guide design

What's known on the subject? and What does the study add? The urethal catheter is a ubiquitous device that has not been modified or improved for safety in the last 20 years, although it can be associated with significant patient harm. This study utilizes force and pressure measurements of the urethral catheter in order to aid in future safety modifications.

OBJECTIVES

• ? To better define urethral catheter balloon pressures and extraction forces during traumatic placement and removal of urethral catheters.
• ? To help guide design for safer urethral catheters.

MATERIALS AND METHODS

• ? Measurements of balloon pressure were made upon filling within the urethra vs the bladder.
• ? Extraction forces were measured upon removal of a catheter with a filled balloon from the bladder.
• ? Models for the bladder and urethra included an ex vivo model (funnel, ‘bladder’, attached to a 30 F tube, ‘urethra’) and fresh human male cadavers.
• ? The mean (sem ) balloon pressures and extraction forces were calculated.

RESULTS

• ? In the ex vivo model, the mean (sem ) pressures upon filling the balloon with 10 mL were on average three‐times higher within the ex vivo‘urethra’ (177 [6] kPa) vs ‘bladder’ (59 [2] kPa) across multiple catheter types.
• ? In the human cadaver, the mean balloon pressure was 1.9‐times higher within the urethra (139 [11] kPa) vs bladder (68 [4] kPa).
• ? Balloon pressure increased non‐linearly during intraurethral filling of both models, resulting in either balloon rupture (silicone catheters) or ‘ballooning’ of the neck of the balloon filling port (latex catheters).
• ? Removal of a filled balloon per the ex vivo model ‘urethra’ and cadaveric urethra, similarly required increasing force with greater balloon fill volumes (e.g. 9.34 [0.44] N for 5 mL vs 41.37 [8.01] N for 10 mL balloon volume).

CONCLUSIONS

• ? Iatrogenic complications from improper urethral catheter use is common.
• ? Catheter balloon pressures and manual extraction forces associated with urethral injury are significantly greater than those found with normal use.
• ? The differences in pressure and force may be incorporated into a safer urethral catheter design, which may significantly reduce iatrogenic urethral injury associated with catheterization.