Can sonographic fetal head circumference measurement help predict Obstetric Anal Sphincter Injury?

OBJECTIVE

Obstetric Anal Sphincter Injuries (OASIS) occur in 2 to 19% of vaginal deliveries in the United States. Neonatal parameters such as birthweight above 4000g or neonatal head circumference above 37 cm are known risk factors for OASIS. We hypothesized that sonographic fetal Head Circumference (sfHC) size assessed by ultrasound antenatally could help predict OASIS.

METHODS

This study is a retrospective cohort study between 2005 and 2016. Antenatal ultrasound Head Circumference (sfHC) assessment, maternal demographics, and labor and delivery data were abstracted and compared in women with and without OASIS.

RESULTS

Of 2057 pregnant women that had sfHC assessment, 121 (5.8%) had OASIS. In the unadjusted analysis, sfHC above the 90^th percentile was associated with OASIS OR 1.12 (1.02-1.23) p=0.015. When adjusted for gestational age at delivery, maternal age, race, prolonged 2^nd stage, BMI, infant gender, and intrapartum oxytocin use, sfHC above the 90^th percentile remained significantly associated with OASIS (OR=1.13, 95% CI 1.00-1.27, p=0.050).

CONCLUSION

In our cohort, sfHC above the 90^th percentile was associated with a greater risk of OASIS. As OASIS significantly impacts short and long-term health outcomes such as perineal pain, dyspareunia, urinary and fecal incontinence, sfHC could be an additional antenatal marker to help clinicians counsel pregnant women about the risk of OASIS.

A Quality-of-Life Comparison of Two Fecal Incontinence Phenotypes: Isolated Fecal Incontinence Versus Concurrent Fecal Incontinence With Constipation

BACKGROUND

Many patients with fecal incontinence report coexisting constipation. This subset of patients has not been well characterized or understood.

OBJECTIVE

The purpose of this study was to report the frequency of fecal incontinence with concurrent constipation and to compare quality-of-life outcomes of patients with fecal incontinence with and without constipation.

DESIGN

This was a prospective cohort study. Survey data, including Fecal Incontinence Severity Index, Constipation Severity Instrument, Fecal Incontinence Quality of Life survey (categorized as lifestyle, coping, depression, and embarrassment), Pelvic Organ Prolapse Inventory and Urinary Distress Inventory surveys, and anorectal physiology testing were obtained.

SETTINGS

The study was conducted as a single-institution study from January 2007 to January 2017.

PATIENTS

Study patients had fecal incontinence presented to a tertiary pelvic floor center.

MAIN OUTCOME MEASURES

Quality-of-life survey findings were measured.

RESULTS

A total of 946 patients with fecal incontinence were identified, and 656 (69.3%) had coexisting constipation. Patients with fecal incontinence with constipation were less likely to report a history of pregnancy (89.2% vs 91.4%; p = 0.001) or complicated delivery, such as requiring instrumentation (9.1% vs 18.1%; p = 0.005), when compared with patients with isolated fecal incontinence. Patients with fecal incontinence with constipation had higher rates of coexisting pelvic organ prolapse (Pelvic Organ Prolapse Inventory: 18.4 vs 8.2; p < 0.01), higher rates of urinary incontinence (Urinary Distress Inventory: 30.2 vs 23.4; p = 0.01), and higher pressure findings on manometry; intussusception on defecography was common. Patients with fecal incontinence with concurrent constipation had less severe incontinence scores at presentation (21.0 vs 23.8; p < 0.001) and yet lower overall health satisfaction (28.9% vs 42.5%; p < 0.001). Quality-of-life scores declined as constipation severity increased for lifestyle, coping, depression, and embarrassment.

LIMITATIONS

This was a single-institution study, and surgeon preference could bias population and anorectal physiology testing.

CONCLUSIONS

Patients with fecal incontinence with concurrent constipation represent a different disease phenotype and have different clinical and anorectal physiology test findings and worse overall quality of life. Treatment of these patients requires careful consideration of prolapse pathology with coordinated treatment of coexisting disorders. See Video Abstract at http://links.lww.com/DCR/A783.

The role of citizen science in addressing grand challenges in food and agriculture research

The power of citizen science to contribute to both science and society is gaining increased recognition, particularly in physics and biology. Although there is a long history of public engagement in agriculture and food science, the term 'citizen science' has rarely been applied to these efforts. Similarly, in the emerging field of citizen science, most new citizen science projects do not focus on food or agriculture. Here, we convened thought leaders from a broad range of fields related to citizen science, agriculture, and food science to highlight key opportunities for bridging these overlapping yet disconnected communities/fields and identify ways to leverage their respective strengths. Specifically, we show that (i) citizen science projects are addressing many grand challenges facing our food systems, as outlined by the United States National Institute of Food and Agriculture, as well as broader Sustainable Development Goals set by the United Nations Development Programme, (ii) there exist emerging opportunities and unique challenges for citizen science in agriculture/food research, and (iii) the greatest opportunities for the development of citizen science projects in agriculture and food science will be gained by using the existing infrastructure and tools of Extension programmes and through the engagement of urban communities. Further, we argue there is no better time to foster greater collaboration between these fields given the trend of shrinking Extension programmes, the increasing need to apply innovative solutions to address rising demands on agricultural systems, and the exponential growth of the field of citizen science.

Abstract P3-04-05: Identification of SAR439859, an orally bioavailable selective estrogen receptor degrader (SERD) that has strong antitumor activity in wild-type and mutant ER+ breast cancer models

Estrogen receptor positive (ER+) breast cancer accounts for 70% of all breast cancers and is primarily treated with endocrine therapy. Approximately 40% of patients on endocrine therapy will become resistant via a number of mechanisms. There is evidence that in many cases ER continues to play a central role, including mutations in ER leading to a constitutively active receptor. Estrogen receptor degraders like fulvestrant are effective in shutting down ER signaling; however, poor pharmaceutical properties limit fulvestrant clinical activity and prevent it from achieving maximum receptor blockade.

We describe the discovery of SAR439859, a novel, orally bioavailable SERD that is a potent antagonist and degrader of ER both in vitro and in vivo. SAR439859 has robust activity in multiple ER+ breast cancer cell lines including cells that are resistant to tamoxifen as well as cell lines harboring ER mutants. Across a large panel of ER+ cells, SAR439859 demonstrated broad and superior ER degradation activity than most SERDs undergoing clinical testing. This leads to a profound inhibition of ER signaling, better inhibition of cell growth and results in improved in vivo efficacy. SAR439859 demonstrated tumor regression in all ER+ BC models including MCF7-ESR1 mutant-Y537S model, as well as patient-derived xenograft model that is resistant to endocrine therapies. Furthermore, SAR439859 displays limited cross-resistance with other class of SERDs.

Taken together, these results suggest that SAR439859 would be of therapeutic benefit in metastatic BC setting for patients harboring wild type or mutant ER. SAR439859 is being advanced toward the clinic.

Citation Format: Shomali M, Cheng J, Koundinya M, Weinstein M, Malkova N, Sun F, Hebert A, Cindachao M, Hoffman D, McManus J, Levit M, Pollard J, Vincent S, Besret L, Adrian F, Winter C, El-Ahmad Y, Halley F, Hsu K, Lager J, Garcia-Echeverria C, Bouaboula M. Identification of SAR439859, an orally bioavailable selective estrogen receptor degrader (SERD) that has strong antitumor activity in wild-type and mutant ER+ breast cancer models [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-05.

Parental Use of Sun Protection for Their Children – Does Skin Colour Matter?

BACKGROUND: Excessive sun exposure during childhood years is a known risk factor for skin cancer. Fifty percent of lifetime UV exposure is acquired by age 19, highlighting the potential for prevention strategies in childhood. Existing guidelines from established pediatric, dermatology and cancer prevention societies are general and not specific to any skin phototype.

OBJECTIVES: Our primary objective was to compare the frequency of adequate sun protection used by parents of children with different skin phototypes. Our secondary objective was to explore parental attitudes and beliefs on sun safety for their children.

DESIGN/METHODS: Parents of children between the ages of 6 months to 6 years were systematically recruited. Parents received self-administered questionnaires containing 40-items that examine the amount of sun protection parents used on their children, as well as their attitudes and beliefs about sun safety. Parents were also requested to self-assess their child’s Fitzpatrick Phototype (FP), and based on this response, they were divided into two groups: “lighter-skinned” (FP I-III) and “darker-skinned” (FP IV-VI). Guidelines from the Canadian Dermatology Association (CDA) on sun safety were used to quantify adequate sun protection.

RESULTS: A total of 183 parents completed the questionnaires, and 150 eligible parents (the first 25 of each FP) were included in the study. Overall, only 17% of parents used adequate sun protection for their children. Parents of lighter-skinned children were significantly more likely to use adequate sun protection (OR=17.0). As their child got older, parents were also significantly less likely to use adequate sun protection for them (OR=0.64). A significantly larger portion of parents of lighter-skin children believe that sun exposure was harmful (OR=14.2) and perceived more value in sun protection (OR=14.2), whereas parents of darker-skin children were significantly more likely to believe that darker skin tones provided more sun protection (OR=4.1).

CONCLUSION: Our study suggests that parental sun protection efforts were overall low, but especially in parents of darker-skinned children. The identified underlying attitudes and beliefs can aid in the design and delivery of sun protection interventions in the future, to ensure sun safety for all children, especially in a multiracial population.

Impaired diffusion tensor imaging findings in the corpus callosum and cingulum may underlie impaired learning and memory abilities in systemic lupus erythematosus

BACKGROUND

Memory impairment is prevalent in systemic lupus erythematosus (SLE); however, its pathogenesis is unknown. In a previous functional magnetic resonance imaging (fMRI) study we demonstrated altered brain activity dynamics and less brain deactivation in patients with SLE as compared with healthy controls, when performing a learning and memory task. Our findings localized this impairment to the default mode network (DMN), and particularly to its anterior medial prefrontal cortex node. In addition, altered networking of the hippocampal subsystem of the DMN was seen in patients with SLE when performing this task, as well as atrophy of the left hippocampus. The present study aimed to search for a structural substrate for the altered recruitment pattern observed in fMRI studies using diffusion tensor imaging (DTI).

PATIENTS AND METHODS

Using DTI, we characterized brain diffusivity in 10 patients with SLE and nine healthy controls. Two tracts associated with the DMN were reconstructed: the corpus callosum (CC) and the cingulum bundle. The CC was segmented according to the Witelson segmentation scheme and the cingulum was segmented into superior and descending bundles.

RESULTS

A significant increase in mean diffusivity (MD) was seen in patients with SLE without neuropsychiatric SLE (NPSLE) as compared with healthy controls in all five segments of the CC (segment 1: p = 0.043; segment 2: p = 0.005; segment 3: p = 0.003; segment 4: p = 0.012; segment 5: p = 0.023) as well as in the descending portion of the left cingulum bundle (p = 0.026).

CONCLUSIONS

Increased MD values in the CC and the left cingulum may indicate impaired organization/reduced integrity of these tracts, which may underlie the abnormal pattern of brain activity recruitment of the DMN observed during a verbal learning and memory task. Taking into account the central role of the left hippocampus in verbal memory, the abnormal integrity of the left cingulum may contribute to the reduced performance of patients with SLE on verbal memory tasks.

MRI-based radiologic scoring system for extent of brain injury in children with hemiplegia

BACKGROUND AND PURPOSE

Brain MR imaging is recommended in children with cerebral palsy. Descriptions of MR imaging findings lack uniformity, due to the absence of a validated quantitative approach. We developed a quantitative scoring method for brain injury based on anatomic MR imaging and examined the reliability and validity in correlation to motor function in children with hemiplegia.

MATERIALS AND METHODS

Twenty-seven children with hemiplegia underwent MR imaging (T1, T2-weighted sequences, DTI) and motor assessment (Manual Ability Classification System, Gross Motor Functional Classification System, Assisting Hand Assessment, Jebsen Taylor Test of Hand Function, and Children's Hand Experience Questionnaire). A scoring system devised in our center was applied to all scans. Radiologic score covered 4 domains: number of affected lobes, volume and type of white matter injury, extent of gray matter damage, and major white matter tract injury. Inter- and intrarater reliability was evaluated and the relationship between radiologic score and motor assessments determined.

RESULTS

Mean total radiologic score was 11.3 ± 4.5 (range 4-18). Good inter- (ρ = 0.909, P < .001) and intrarater (ρ = 0.926, P = < .001) reliability was demonstrated. Radiologic score correlated significantly with manual ability classification systems (ρ = 0.708, P < .001), and with motor assessments (assisting hand assessment [ρ = -0.753, P < .001]; Jebsen Taylor test of hand function [ρ = 0. 766, P < .001]; children's hand experience questionnaire [ρ = -0. 716, P < .001]), as well as with DTI parameters.

CONCLUSIONS

We present a novel MR imaging-based scoring system that demonstrated high inter- and intrarater reliability and significant associations with manual ability classification systems and motor evaluations. This score provides a standardized radiologic assessment of brain injury extent in hemiplegic patients with predominantly unilateral injury, allowing comparison between groups, and providing an additional tool for counseling families.

Isolated mild white matter signal changes in preterm infants: a regional approach for comparison of cranial ultrasound and MRI findings

OBJECTIVE

To compare echogenicity detected using cranial ultrasound (cUS) and diffuse excessive high signal intensity (DEHSI) detected using magnetic resonance imaging (MRI) by identical region-based scoring criteria in preterm infants. To explore the association between these white matter (WM) signal changes with early neurobehavior.

STUDY DESIGN

Forty-nine pre-selected premature infants with only echogenicity on a first routine cUS1 underwent MRI and a repeated cUS2 at term equivalent age. Echogenicity and DEHSI were graded in various brain areas and diffusivity values were calculated. Neurobehavior was assessed using the Rapid Neonatal Neurobehavioral Assessment Procedure.

RESULT

WM signal changes were significantly higher on cUS1 than cUS2; and higher in MRI than cUS2 in posterior regions. Infants with DEHSI demonstrated reduced tissue integrity. Imaging findings were not correlated with early neurobehavior.

CONCLUSION

Echogenicity and DEHSI likely represent the same phenomenon. Reduction of over-interpretation of WM signal changes may help define criteria for the judicious use of imaging in routine follow-up of premature infants.

In patients with rectoceles and obstructed defecation syndrome, surgery should be the option of last resort

BACKGROUND

The indications for operation in patients with obstructed defecation syndrome (ODS) with rectocele are not well defined.

METHODS

A total of 90 female patients with ODS and rectocele were prospectively evaluated and treated with fiber supplements and biofeedback training. Univariate and multivariate regression was used to determine factors predictive of failing medical management.

RESULTS

Obstructive symptoms were the most prevalent presenting complaint (82.2%). Ultimately, 71.1% of patients responded to medical management and biofeedback. Multivariate regression analysis suggested that the presence of internal intussusception was associated with a lower chance of undergoing surgery to address ODS symptoms [odds ratio 0.18; P = .05], whereas inability to expel balloon, contrast retention on defecography, and splinting were not (P ≥ .15).

CONCLUSION

Rectoceles with concomitant intussusception in patients with ODS appear to portend a favorable response to biofeedback and medical management. We argue that all patients considered for surgery for rectoceles because of ODS should first undergo appropriate bowel retraining.

Anatomical disruption and length-tension dysfunction of anal sphincter complex muscles in women with fecal incontinence

BACKGROUND

Anal sphincter complex muscles, the internal anal sphincter, external anal sphincter, and puborectalis muscles, play an important role in the anal continence mechanism. Patients with symptoms of fecal incontinence have weak anal sphincter complex muscles; however, their length-tension properties and relationship to anatomical disruption have never been studied.

OBJECTIVE

This study aimed to assess the anatomy of the anal sphincter complex muscles with the use of a 3-dimensional ultrasound imaging system and to determine the relationship between the anatomical defects and the length-tension property of external anal sphincter and puborectalis muscles in women with incontinence symptoms and in control subjects.

DESIGN

Severity of anal sphincter muscle damage was determined by static and dynamic 3-dimensional ultrasound imaging. The length-tension property was determined by anal and vaginal pressure with the use of custom-designed probes.

PATIENTS

Forty-four asymptomatic controls and 24 incontinent patients participated in this study.

MAIN OUTCOME MEASURES

The anatomical defects and length-tension dysfunction of anal sphincter complex muscles in patients with fecal incontinence were evaluated.

RESULTS

The prevalence of injury to sphincter muscles is significantly greater in the incontinent patients than in the controls. Eighty-five percent of patients but only 9% controls reveal damage to ≥2 of the 3 muscles of the anal sphincter complex. Anal and vaginal squeeze pressures increased with the increase in the probe size (length-tension curve) in the majority of controls. In patients, the increase in anal and vaginal squeeze pressures was either significantly smaller than in controls or it decreased with the increasing probe size (abnormal length-tension).

LIMITATIONS

We studied patients with severe symptoms. Whether our findings are applicable to patients with mild to moderate symptoms remains to be determined.

CONCLUSIONS

The length-tension property of the external anal sphincter and puborectalis muscles is significantly impaired in incontinent patients. Our findings have therapeutic implications for the treatment of anal incontinence.

Are rectoceles the cause or the result of obstructed defaecation syndrome? A prospective anorectal physiology study

AIM

To determine the relationship between obstructed defaecation syndrome (ODS) and rectoceles.

METHOD

From December 2007 to November 2011, all female patients with ODS were prospectively evaluated with full interview, clinical examination and anorectal physiology testing. The characteristics of patients with and without rectoceles were compared, and logistic regression was utilized to identify factors predictive of patients having a rectocele beyond the introitus.

RESULTS

Of 239 patients with ODS, 90 (mean age: 52.3 ± 1.7 years) had a rectocele. Patients with rectoceles (R+) had a similar prevalence of incomplete emptying compared with patients with no rectocele (R-) (P ≥ 0.21), but only R+ patients reported splinting with defaecation (36.7% vs 0%; P < 0.0001). Anorectal manometry measurements, including mean resting pressure, maximum resting pressure and maximum squeeze pressure, were similar between groups (P ≥ 0.12). There were also no significant differences in rectal compliance (maximum tolerated volume) or rectal sensitivity (volume of first sensation) (P ≥ 0.65). R+ patients had greater difficulty expelling a 60 cm(3) balloon (70.1% R+ patients vs 57.5% R- patients; P = 0.05), but the prevalence of pelvic floor dyssynergia, as quantified by nonrelaxation on electromyography (EMG) testing, was similar to that of R- patients (P = 0.49). Logistic regression suggested that only difficulty with balloon expulsion was associated with higher odds of having a rectocele (OR = 3.00; P = 0.002), whereas mean resting pressure, EMG nonrelaxation and symptoms of incomplete emptying were not (P ≥ 0.12).

CONCLUSION

Rectoceles are not associated with an increased severity of ODS-type symptoms, anorectal abnormalities or pelvic floor dyssynergia in patients with ODS. This suggests that rectoceles may be the result, rather than the cause, of ODS.

Parent-of-origin in individuals with familial neurofibromatosis type 1 and optic pathway gliomas

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant cancer syndromes worldwide. Individuals with NF1 have a wide variety of clinical features including a strongly increased risk for pediatric brain tumors. The etiology of pediatric brain tumor development in NF1 is largely unknown. Recent studies have highlighted the contribution of parent-of-origin effects to tumorigenesis in sporadic cancers and cancer predisposition syndromes; however, there is limited data on this effect for cancers arising in NF1. To increase our understanding of brain tumor development in NF1, we conducted a multi-center retrospective chart review of 240 individuals with familial NF1 who were diagnosed with a pediatric brain tumor (optic pathway glioma; OPG) to determine whether a parent-of-origin effect exists overall or by the patient's sex. Overall, 50 % of individuals with familial NF1 and an OPG inherited the NF1 gene from their mother. Similarly, by sex, both males and females were as likely to inherit the NF1 gene from their mother as from their father, with 52 % and 48 % of females and males with OPGs inheriting the NF1 gene from their mother. In conclusion, in contrast to findings from other studies of sporadic cancers and cancer predisposition syndromes, our results indicate no parent-of-origin effect overall or by patient sex for OPGs in NF1.

First do no harm: The dangers of mineral oil

Chronic constipation is a very common problem in the paediatric population, and a particularly frequent issue in the management of neurologically impaired children. The use of mineral oil in the treatment of constipation has been well accepted because of its efficacy and infrequent side effects. The case of a three and a half-year-old girl with spastic quadriplegic cerebral palsy, who was admitted to hospital for investigation of increasing tachypnea and respiratory distress over a two-month period, is presented. This case highlights lipoid pneumonia due to mineral oil aspiration, which is a recognized severe complication of this medication, and emphasizes the need for a heightened awareness among caregivers about the potential dangers of inappropriate mineral oil use.

Collaborative study for the establishment of replacement batches for human coagulation factor IX concentrate reference standards

The European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) batch 1, the World Health Organisation (WHO) 3rd International Standard, Human (IS, 96/854) and the FDA Standard for human blood coagulation Factor IX concentrate have been available since 1996, following their establishment by a common collaborative study. Due to dwindling stocks of all three standards, a new WHO-EDQM-FDA tri-partite collaborative study was launched to establish replacement batches. Thirty laboratories from fourteen countries took part in the collaborative study to assign potency values to candidate preparations. Three candidates, one of recombinant and two of human plasma-derived origins, were assayed against the 3rd IS for Blood Coagulation Factor IX, Concentrate, Human (96/854). The 3rd IS for Blood Coagulation Factors II, VII, IX and X, Plasma, Human (99/826) was also included to evaluate the relationship between the factor IX plasma and concentrate unitage. Thirty-two sets of clotting assay results and two sets of chromogenic assay data were analysed. There was a significant difference in potency estimates by these two methods for the recombinant candidate (sample B) and the plasma IS (sample P). Similar potency values were obtained for the plasma derived products (monoclonal antibody- and chromatography-purified factor IX, samples C and D) by clotting and chromogenic assays. For the clotting assays, intra-laboratory variability (GCV) was found to range from 0.5 - 21.7%, with the GCV for the majority of laboratories being less than 10%. Good inter-laboratory agreement, with the majority of the GCV being less than 10% (GCV range = 4.7 - 10.6 %) was also obtained. The mean potency values estimated by the clotting assay using plasma as pre-diluent (as directed by the Ph. Eur. general chapter method) did not differ from values obtained using buffer. Taking into account the preliminary stability data, the intra- and inter-laboratory variability, and the differences between the clotting and chromogenic assay results, sample C (07/182) was established as the Human coagulation factor IX concentrate BRP batch 2, with a potency value of 7.9 IU/ampoule assigned with clotting assay results. As an outcome of this tri-partite collaborative study, the same sample C (07/182) has also been adopted as the 4th International Standard for Blood Coagulation Factor IX, Concentrate, Human by the Expert Committee on Biological Standardisation (ECBS) of the World Health Organisation (WHO), and as the replacement batch for the reference standard for Human coagulation factor IX concentrate by the FDA.

A robotic manipulator for handling TLD badges

A prototype system for automatic handling of Harshaw/Bicron (now ThermoFisher Scientific) thermoluminescent dosimetry (TLD) badges, which is based on a robotic arm, was designed and built. The robot performs the loading and unloading of the TLD cards in the badges and transports them between the loading/unloading station and magazine stations. For quality assurance, a sticker containing the worker's details printed in barcode format was added to the badge. Automatic on-line identification is performed for checking the correlation between the badge and the TLD card number.

Closure mechanism of the anal canal in women: assessed by three-dimensional ultrasound imaging

PURPOSE

To describe the functional correlates of anal canal anatomy using 3 dimensional ultrasound imaging.

METHODS

Ten nulliparous women were studied by using a 10-cm bag of 20-mm diameter. The bag was placed along the anal canal and inflated with 20 to 45 ml water, in 5-ml increments. At each volume, a three-dimensional ultrasound volume of the anal canal was obtained while the subjects were at rest and squeeze. The ultrasound images were analyzed to determine the relationship between the bag cross-sectional area and bag pressure.

RESULTS

At low distension volumes, the bag is shaped like an "hourglass." The flared ends of the funnels correspond with the proximal and distal margins of the puborectalis muscle and external anal sphincter respectively. With increasing bag volumes, the length of completely closed segment of anal canal decreased. The last anal segment to open at rest was the one surrounded by all three structures. Anal contraction resulted in reduction of the anal canal cross-sectional area; the least compliant part of the anal canal was the one surrounded by external anal sphincter.

CONCLUSION

The internal anal sphincter, external anal sphincter, and puborectalis muscle are all involved in the anal canal closure function. During contraction, the external anal sphincter is the strongest component of anal canal closure mechanism.