Correlation between gross anatomical topography, sectional sheet plastination, microscopic anatomy and endoanal sonography of the anal sphincter complex in human males

A New Approach to Ultra-Low Anterior Resection-Intersphincteric Dissection With Total Hiatal Ligament Excision for Very Low Rectal Cancer Located in the Posterior Wall of the Rectum: A More Satisfactory Technique for Local Recurrence Control

BACKGROUND

The hiatal ligament, as the anatomical landmark for the completion of total mesorectal excision (TME) for ultra-low rectal cancer, represents a continuation of the longitudinal muscle of the rectum. It receives vascular supply from the median sacral artery and contains lymphatic vessels. In cases where ultra-low rectal cancer is located in the posterior rectal wall, the hiatal ligament may theoretically serve as an anatomical region susceptible to direct tumor cell spread or distant metastasis.

OBJECTIVE

To evaluate the effect of circumferential tumor location (CTL) on postoperative survival of low rectal cancer and to determine the effect of total hiatal ligament excision (THLE) on the prognosis of patients with posterior rectal cancer.

METHODS

Patients with ultra-low rectal cancer who underwent laparoscopic surgery between March 2014 and October 2021 were enrolled in this study. Propensity score matching (PSM) analysis was used to compare the clinicopathological characteristics and prognosis of patients in the posterior group and the non-posterior group. Prognostic factors were identified using COX regression. PSM analysis was also used in the posterior tumor subgroup to compare the clinicopathological characteristics and prognosis of patients in the hiatal ligament traditional transection (HLTT) and THLE groups.

RESULTS

After PSM, OS, and DFS were comparable between the posterior and non-posterior groups. Similarly, no difference was noted in the local recurrence rate between the two groups (p = 0.23). The prognosis of ultra-low rectal cancer was not affected by CTL. However, the local recurrence rate was significantly lower in the THLE group compared with the HLTT group (p = 0.023). Multivariate analysis of the posterior group identified CRM, TNM stage III, and HLTT as independent risk factors for local recurrence-free survival.

CONCLUSIONS

CTL is not a prognostic risk factor for low rectal cancer. In posterior wall tumors, THLE significantly reduces the local recurrence rate for low rectal cancer.

The Female Pelvic Floor Fascia Anatomy: A Systematic Search and Review

The female pelvis is a complex anatomical region comprising the pelvic organs, muscles, neurovascular supplies, and fasciae. The anatomy of the pelvic floor and its fascial components are currently poorly described and misunderstood. This systematic search and review aimed to explore and summarize the current state of knowledge on the fascial anatomy of the pelvic floor in women. Methods: A systematic search was performed using Medline and Scopus databases. A synthesis of the findings with a critical appraisal was subsequently carried out. The risk of bias was assessed with the Anatomical Quality Assurance Tool. Results: A total of 39 articles, involving 1192 women, were included in the review. Although the perineal membrane, tendinous arch of pelvic fascia, pubourethral ligaments, rectovaginal fascia, and perineal body were the most frequently described structures, uncertainties were identified in micro- and macro-anatomy. The risk of bias was scored as low in 16 studies (41%), unclear in 3 studies (8%), and high in 20 studies (51%). Conclusions: This review provides the best available evidence on the female anatomy of the pelvic floor fasciae. Future studies should be conducted to clarify the discrepancies highlighted and accurately describe the pelvic floor fasciae.

Generation of myogenic progenitor cell-derived smooth muscle cells for sphincter regeneration

BACKGROUND

Degeneration of smooth muscles in sphincters can cause debilitating diseases such as fecal incontinence. Skeletal muscle-derived cells have been effectively used in clinics for the regeneration of the skeletal muscle sphincters, such as the external anal or urinary sphincter. However, little is known about the in vitro smooth muscle differentiation potential and in vivo regenerative potential of skeletal muscle-derived cells.

METHODS

Myogenic progenitor cells (MPC) were isolated from the skeletal muscle and analyzed by flow cytometry and in vitro differentiation assays. The differentiation of MPC to smooth muscle cells (MPC-SMC) was evaluated by immunofluorescence, flow cytometry, patch-clamp, collagen contraction, and microarray gene expression analysis. In vivo engraftment of MPC-SMC was monitored by transplanting reporter protein-expressing cells into the pyloric sphincter of immunodeficient mice.

RESULTS

MPC derived from human skeletal muscle expressed mesenchymal surface markers and exhibit skeletal myogenic differentiation potential in vitro. In contrast, they lack hematopoietic surface marker, as well as adipogenic, osteogenic, and chondrogenic differentiation potential in vitro. Cultivation of MPC in smooth muscle differentiation medium significantly increases the fraction of alpha smooth muscle actin (aSMA) and smoothelin-positive cells, while leaving the number of desmin-positive cells unchanged. Smooth muscle-differentiated MPC (MPC-SMC) exhibit increased expression of smooth muscle-related genes, significantly enhanced numbers of CD146- and CD49a-positive cells, and in vitro contractility and express functional Cav and Kv channels. MPC to MPC-SMC differentiation was also accompanied by a reduction in their skeletal muscle differentiation potential. Upon removal of the smooth muscle differentiation medium, a major fraction of MPC-SMC remained positive for aSMA, suggesting the definitive acquisition of their phenotype. Transplantation of murine MPC-SMC into the mouse pyloric sphincter revealed engraftment of MPC-SMC based on aSMA protein expression within the host smooth muscle tissue.

CONCLUSIONS

Our work confirms the ability of MPC to give rise to smooth muscle cells (MPC-SMC) with a well-defined and stable phenotype. Moreover, the engraftment of in vitro-differentiated murine MPC-SMC into the pyloric sphincter in vivo underscores the potential of this cell population as a novel cell therapeutic treatment for smooth muscle regeneration of sphincters.

Does exclusion of subcutaneous external anal sphincter on exoanal imaging matter?

OBJECTIVE

There is some speculation that an intact distal anal sphincter complex is of decisive importance for continence, although the external anal sphincter (EAS) is considered to be a single functional and anatomical entity. On tomographic translabial ultrasound (TLUS), the caudal slice at the level of the subcutaneous EAS is currently omitted from the diagnostic algorithm due to the prevalence of artifact at that level. The aim of this study was to determine the predictive value of assessment of the subcutaneous EAS on tomographic TLUS for anal incontinence (AI).

METHODS

This was a retrospective study of 463 women seen at our urogynecological service in 2015. All underwent a standardized questionnaire, including determination of St Mark's incontinence score (SMIS), clinical examination and three-/four-dimensional TLUS. On tomographic TLUS, EAS defect angles in slices one to seven were measured on maximum pelvic floor muscle contraction. A slice was defined as positive for a defect if the defect angle was ≥ 30°. The association between significant subcutaneous EAS trauma (i.e. defect angle of ≥ 30° in slice seven) and symptoms of AI, symptom bother score and SMIS was assessed. The performances of the standard six-slice model and the seven-slice model, including the subcutaneous EAS, in the prediction of AI were compared.

RESULTS

While there was a highly significant association between all measures of AI and significant EAS trauma in slice seven, addition of the seventh slice to the existing six-slice model did not improve the predictive value for AI.

CONCLUSION

As inclusion of the subcutaneous slice of the EAS on tomographic TLUS does not seem to improve the predictive value for AI, the current methodology for assessment of EAS trauma on tomographic TLUS can remain unchanged. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Extraction of DNA from plastinated tissues

INTRODUCTION

Plastination allows anatomical samples to be preserved in excellent condition for an indefinite period, free of formalin, and in a format that allows biosafe manipulation by students, academics, and researchers. As with other tissue preservation techniques, it is important to establish the level of conservation of deoxyribonucleic acid (DNA) for use in future applications. The object of the present work was to extract and evaluate DNA from plastinated tissues.

METHODS

We used samples of liver from Canis lupus familiaris and skeletal muscle from Rattus norvegicus, Sprague-Dawley strain, extracted from specimens plastinated with silicone at room temperature. The tissue samples were deplastinated by incubation in 5% sodium methoxide dissolved in methanol for 24 or 48 h. The samples were divided into two equal parts and DNA was extracted using two different protocols. After extraction, the DNA was quantified by fluorometry and its integrity was assessed by electrophoresis in a 1% agarose gel.

RESULTS AND DISCUSSION

A high yield of DNA was obtained from the deplastinated samples and the DNA was intact. Plastinated tissues have proven to be stable and easily managed. They can also be used for examination under light and electron microscopes. The DNA extraction technique used here allowed us to obtain intact DNA from samples plastinated with silicone at room temperature, without previous fixing. This technique may allow tissue specimens to be preserved for retrospective studies of archived samples of normal and pathological anatomy in the fields of basic, clinical, forensic, and epidemiological sciences.

CONCLUSIONS

The extracted DNA was intact and suitable for use in subsequent applications. Obtaining whole DNA from plastinated samples using tissue preservation protocols that preserve the tissue for use in subsequent applications, like real-time PCR, opens up many possibilities, with applications in the basic and clinical sciences, epidemiology, and forensic science.

Ultrasound-Guided Needle Electromyography of the External Anal Sphincter

BACKGROUND

Anal sphincter needle electromyography (EMG) is a useful tool to evaluate various neurologic lesions. However, landmark-based needle placement has risks of missing the intended target including risk of bowel penetration. Ultrasound guidance has been widely used to enhance needle placement for various interventional procedures, but it has not been previously reported for use in anal sphincter EMG.

OBJECTIVE

To demonstrate the accuracy of ultrasound-guided needle insertion into the external anal sphincter (EAS).

DESIGN

Observational study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

A single live male participant and six fresh cadavers.

METHODS

A preliminary study was conducted in a single live male participant to investigate the utility of ultrasonography imaging for the EAS and proper transducer location. After this preliminary study, 12 sides of the EAS in six fresh cadavers were assessed. A hooked fine wire was inserted into the EAS under ultrasound guidance.

MAIN OUTCOME MEASURES

Accuracy of needle placement was assessed after cadaver dissection.

RESULTS

The EAS was easily identified with ultrasound in preliminary and cadaver studies. The needle tips were located in the EAS in 11 of 12 cadavers.

CONCLUSIONS

Ultrasound-guided needle EMG of the EAS is convenient and accurate in cadavers and may be useful in clinical practice. Further studies comparing ultrasound-guided and landmark-guided needle EMG of the EAS in live patients will be needed.

A PASSIVE STATE SIMULATION OF AN ANAL SPHINCTER USING SIMMECHANICS

Nowadays, different mechanical artificial sphincters can be found implanted in human beings, trying to overcome a deficiency in the performance of the natural one. However, they do not take into account the natural anal sphincter’s (AS) dimensions, and autonomous response; they also lack in basic contraction and relaxation properties. In this paper, by addressing the AS behavior, an AS model designed with Matlab/SimMechanics is shown. The model comprises bodies of concentrated mass interconnected by springs. The mass–spring system is arranged in concentric rings where every concentrated mass is interconnected by a spring. Each spring takes specific stiffness, which varies with length, in accordance to an experimental curve. The system described can be loaded or unloaded, describing then the muscle behavior.

Each element that forms the model of rings is subject to displacements caused by forces of traction and compression, when a radial force is applied from the center towards the inner ring. The springs of the inner ring experience forces of traction, whereas the springs that connect the body of the inner ring with the outer ring perpendicularly are submitted to compression forces.The data used in the proposed model corresponded to dimensions of the humanAS: width, height, rigidity, stress, tension, basically obtaining an initial deformation behavior according to the sphincter in the passive state. The model remained stable with some mechanical oscillations due to the elastic elements; by modifying one of the parameters, the behavior became unstable and unmanageable. It was verified that it is a sensitive model when modifying the initial conditions that the concrete data requires in case of reproducing the sphincter muscle with particular dimensions.

MRI of anal canal: normal anatomy, imaging protocol, and perianal fistulas: Part 1

Anal complaints are very common in the general population and are caused by a variety of disorders mostly benign in nature. The aim of this article is to provide the radiologist with a detailed description of the MRI anatomy and technique, and an overview of the various diseases most commonly presenting with anal pain, by descriptions and illustrative examples of MRI features of each entity.

Helpfulness of rectoanal endosonography in diagnosis of sexual abuse in a child

BACKGROUND

Clinical importance of sexual abuse in children has rapidly expanded in recent years, but despite of it, the lack of medical signs in the vast majority of sexual abuse cases, makes it difficult to assess. Given that, owing to our prior experience in endosonography (EUS) of the anal canal in child with anorectal malformations, we wanted to test EUS as a diagnostic method of sexual abuse in a child.

PURPOSE

The purpose of our study is to present our experience in the use of anorectal EUS among children with suspected sexual abuse.

MATERIALS/METHODS

We present 40 consecutive patients (34 boys and 6 girls, age: 10months-13years) recruited from April 2010 to December 2012, with suspected sexual abuse those made a transrectal EUS.

RESULTS

The procedure was well-tolerated in all patients without complications. Rectoanal EUS findings were normal in 27 patients and showed a partial interruption in the external anal sphincter in 8, scars in 2, double rail image in 2, and rectal wall hematoma in 1.

CONCLUSIONS

The interpretation of findings in children depends of historical, physical, and laboratory findings. We believe that anal EUS is another aid in the constellation of clinical factors that could help in diagnostic of sexual abuse.

Plastination in Anatomy Learning: An Experience at Cambridge University

Due to lack of objective data, the benefits of using plastination in combination with wet dissection in teaching gross anatomy are unknown. The aim of this study was to obtain objective evidence from students regarding the effectiveness of combining plastinated specimens (PS) with an established gross anatomy education program at Cambridge University that uses wet cadaver dissection and small-group tutorials. For a complete academic year, a total of 135 PS were used alongside wet cadaver dissections. The PS were also available for small-group tutorials. An anonymous closed questionnaire, using a 5-point numerical-estimation Likert scale, was used to gather information relating to the effectiveness of the PS. The level of student satisfaction with the combined use of wet dissections and PS was high, although higher (p<.05) for second-year students (98.4%) than for first-year students (95.5%). Students felt the specimens allowed them to see details that were often more difficult to identify in their dissections, for instance nerves. Voluntary use of PS was higher (p<.01) for second-year students (96.9%), who had previously experienced anatomy teaching with cadaver dissection alone, than for first-year students (77.7%). Overall, 97.7% of all students thought that the PS helped them understand and learn anatomy. All students surveyed (100%) recommended the use of PS in the future. Students considered the use of PS in the dissection room combined with wet cadaver dissection to be beneficial when learning anatomy, particularly when combined with their use during small-group tutorials.

Anal endosonography and bowel function in patients undergoing different types of endorectal pull-through procedures for Hirschsprung disease

BACKGROUND

The reasons for fecal incontinence after surgery for Hirschsprung disease (HD) remain unclear. The aim of this study was to examine the anal sphincters by anal endosonography and manometry after transanal endorectal pull-through, with or without laparotomy or laparoscopy, in HD patients. Furthermore, we aimed to correlate these findings to bowel function.

PATIENTS AND METHODS

Fifty-two HD patients were followed after endorectal pull-through. Anal endosonography and manometry were performed without sedation at the age of 3 to 16 years.

RESULTS

Endosonographic internal anal sphincter (IAS) defects were found in 24/50 patients, more frequently after transanal than transabdominal procedures (69 vs. 19%, p=0.001). In a multiple variable logistic regression model, operative approach was the only significant predictor for IAS defects. Anal resting pressure (median 40mm Hg, range 15-120) was not correlated to presence of IAS defects. Daily fecal incontinence occurred more often in patients with IAS defects (54 vs. 25%, p=0.03).

CONCLUSIONS

Postoperative IAS defects were frequently detected and were associated with daily fecal incontinence. IAS defects occurred more often after solely transanal procedures. We propose that these surgical approaches are compared in a randomized controlled trial before solely transanal endorectal pull-through is performed as a routine procedure.

Nerves in the intersphincteric space of the human anal canal with special reference to their continuation to the enteric nerve plexus of the rectum

In the intersphincteric space of the anal canal, nerves are thought to "change" from autonomic to somatic at the level of the squamous-columnar epithelial junction of the anal canal. To compare the nerve configuration in the intersphincteric space with the configuration in adjacent areas of the human rectum, we immunohistochemically assessed tissue samples from 12 donated cadavers, using antibodies to S100, neuronal nitric oxide synthase (nNOS), and tyrosine hydroxylase (TH). Antibody to S100 revealed a clear difference in intramuscular nerve distribution patterns between the circular and longitudinal muscle layers of the most inferior part of the rectum, with the former having a plexus-like configuration, while the latter contained short, longitudinally running nerves. Most of the intramural ganglion cells in the anal canal were restricted to above the epithelial junction, but some were located just below that level. Near or at the level of the epithelial junction, the nerves along the rectal adventitia and Auerbach's nerve plexus joined to form intersphincteric nerves, with all these nerves containing both nNOS-positive parasympathetic and TH-positive sympathetic nerve fibers. Thus, it was histologically difficult to distinguish somatic intersphincteric nerves from the autonomic Auerbach's plexus. In the intersphincteric space, the autonomic nerve elements with intrapelvic courses seemed to "borrow" a nerve pathway in the peripheral branches of the pudendal nerve. Injury to the intersphincteric nerve during surgery may result in loss of innervation in the major part of the internal anal sphincter.

Endoanorectal ultrasonography

Endoanorectal ultrasonography (EARUS) may be used for diagnosing various anorectal disorders. EARUS is easy to perform, has a short learning curve, and causes less discomfort than routine digital examination. Anal sphincters can be clearly visualized, and one can easily distinguish between the internal (hypoechoic) and external (hyperechoic) anal sphincters. Other pelvic floor structures, like the puborectalis muscle, can also be visualized. The use of contrast agents can increase the accuracy of EARUS in the assessment of perianal fistulae. In addition, EARUS is an excellent alternative to expensive magnetic resonance imaging. Besides its use in incontinence and perianal sepsis, the presence of slight or massive submucosal invasion in early rectal cancer may be imaged in greater detail. With 3-dimensional EARUS, it is possible to diagnose the anorectal diseases, in multiplane, with high spatial resolution, adding important information about the therapeutic decision. The normal sonographic anatomy of the anorectum, sonographic findings of anorectal diseases, and indications and limitations of endosonography with complementary techniques such as transvaginal and transperineal ultrasound are reviewed in this article.

Endosonographic evaluation of anal sphincters in healthy children

PURPOSE

To describe the endosonographic anatomy of anal sphincters in healthy children and to evaluate the reproducibility of sphincter thickness measurements.

METHODS

Forty-five healthy children with median age of 3.6 years (range, 1.0-14.5 years) were studied while under general anesthesia for minor surgery. Anal endosonography was performed with a 7- to 10-MHz rotating transducer with a diameter of 19 mm. The internal anal sphincter (IAS) and the external anal sphincter (EAS) were assessed by 2 independent observers.

RESULTS

IAS and EAS were identified in all children. The mean thickness of IAS and EAS were 1.3 mm and 5.3 mm, respectively. Identification of the inner and outer border of IAS was difficult, especially in children younger than 3 years. The thickness of EAS was easier to assess, and the interrater reliability for EAS thickness measurements was excellent. EAS thickness was positively correlated with the children's age. Reflectivity varied within the EAS with frequent hyporeflective areas.

CONCLUSIONS

Anal endosonography provided visualization of the IAS and EAS in children. Assessment of exact IAS thickness was difficult, especially in the youngest children. Mean EAS thickness was 5.3 mm, increasing with age. Hyporeflective areas of the intact EAS should not be misinterpreted as sphincter defects.