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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract AimExcellent understanding of the arrangement of fasciae and nerves surrounding the rectum is necessary for total mesorectal excision (TME). However, the fasciae anterolateral to the mesorectum and surrounding the low-rectum are still poorly understood. We studied the perirectal fascia along the complete length of the rectum in en-bloc cadaveric specimens and the University Medical Center of Utrecht (UMCU) pelvic dataset, and describe implications for TME. MethodsFour donated human adult cadaveric specimens (two males, two females) were obtained through the Leeds GIFT Research Tissue Programme. Paraffin-embedded blocks were produced and serially sectioned at 50 and 250 m intervals. Whole mount sections were stained with haematoxylin & eosin, Masson's trichrome and Millers' elastin. Additionally, the UMCU pelvic dataset including digitalised cryosections of a female pelvis in three axes, was studied. ResultsMultiple fascial layers surrounded the upper rectum. In the 'holy plane' of TME, laminae merged with the mesorectal and parietal fascia. Nerves ran directly laterally to the mesorectal fascia. More caudally, the mesorectal fascia approached the longitudinal layer of the rectal muscularis propria 3 with the neurovascular bundles situated anterolaterally. The mesorectal fascia had a variable appearance in terms of thickness and completeness, which was most prominent anterolaterally. ConclusionOptimal TME requires dissection on the mesorectal fascia to preserve the nerves. Rectal surgeons are challenged in doing so as the mesorectal fascia varies in thickness and is often absent in some areas. More caudally, a wider excision may be needed to avoid incomplete specimens.4

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Aim Dissection of the perineal body (PB) during abdominoperineal excision (APE) for low rectal cancer is often difficult due to the lack of a natural plane of dissection. Understanding the PB and its relation to the anorectum is essential to permit safe dissection during the perineal phase of the operation and avoid damage to the anorectum and urogenital organs. This study describes the anatomy and histology of the PB relevant to APE. Method Six human adult cadaver pelvic exenteration specimens (three male, three female) from the Leeds GIFT Research Tissue Programme were studied. Paraffin‐embedded mega‐blocks were produced and serially sectioned at 50‐ and 250‐μm intervals. Sections were stained by immunohistochemistry to show collagen, elastin and smooth muscle. Results The PB was cylindrically shaped in the male specimens and wedge‐shaped in the female ones. Although centrally located between the anal and urogenital triangles, it was nearly completely formed by muscle fibres derived from the rectal muscularis propria. Thick bundles of smooth muscle, mostly arising from the longitudinal muscle, inserted into the PB and levator ani muscle (LAM). The recto‐urethralis muscle originated from the PB and separated the anterolateral PB from the urogenital organs. Conclusion Smooth muscle fibres derived from the rectal muscularis propria extend into the PB and LAM and appear to fix the anorectum. Dissection of the PB during APE is safe only when the smooth muscle fibres that extend into the PB are divided.