The anatomy of the perineal body in relation to abdominoperineal excision for low rectal cancer

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.

Understanding the surgical pitfalls in total mesorectal excision: Investigating the histology of the perirectal fascia and the pelvic autonomic nerves

AIM

Excellent understanding of fasciae and nerves surrounding the rectum is necessary for total mesorectal excision (TME). However, fasciae anterolateral to the rectum and surrounding the low rectum are still poorly understood. We studied the perirectal fascia enfolding the extraperitoneally located part of the rectum in en-bloc cadaveric specimens and the University Medical Center Utrecht (UMCU) pelvic dataset, and describe implications for TME.

METHODS

Four 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 μm 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.

RESULTS

The mid and lower rectum were surrounded by a multi-layered perirectal fascia, of which the mesorectal fascia (MRF) and parietal fascia bordered the 'holy plane'. There was no extra constant fascia forming a potential surgical plane. Nerves ran laterally to the MRF. More caudally, the mesorectal fat strongly reduced and the MRF approached the rectal muscularis propria. The MRF had a variable appearance in terms of thickness and completeness, most prominently at the anterolateral lower rectum.

CONCLUSION

Dissection onto the MRF allows nerve preservation in TME. Rectal surgeons are challenged in doing so as the MRF varies in thickness and shows gaps, most prominently at the anterolateral lower rectum. At this site, the risk of entering the mesorectum is great and may result in an incomplete specimen.

Whole mount microscopic sections reveal that Denonvilliers' fascia is one entity and adherent to the mesorectal fascia; implications for the anterior plane in total mesorectal excision?

BACKGROUND

Excellent anatomical knowledge of the rectum and surrounding structures is essential for total mesorectal excision (TME). Denonviliers' fascia (DVF) has been frequently studied, though the optimal anterior plane in TME is still disputed. The relationship of the lateral edges of DVF to the autonomic nerves and mesorectal fascia is unclear. We studied whole mout microscopic sections of en-bloc cadaveric pelvic exenteration and describe implications for TME.

METHODS

Four donated human adult cadaveric specimens (two males, two females) were obtained from the Leeds GIFT Research Tissue Programme. Paraffin-embedded mega blocks were produced and serially sectioned at 50 and 250 μm intervals. Sections were stained with haematoxylin & eosin, Masson's trichrome and Millers' elastin. Additionally, a series of eleven human fetal specimens (embryonic age of 9-20 weeks) were studied.

RESULTS

DVF consisted of multiple fascial condensations of collagen and smooth muscle fibres and was indistinguishable from the anterior mesorectal fascia and the prostatic fascia or posterior vaginal wall. The lateral edges of DVF appeared fan-shaped and the most posterior part was continuous with the mesorectal fascia. Fasciae were not identified in fetal specimens.

CONCLUSION

DVF is adherent to and continuous with the mesorectal fascia. Optimal surgical dissection during TME should be carried out anterior to DVF to ensure radical removal, particularly for anterior tumours. Autonomic nerves are at risk, but can be preserved by closely following the mesorectal fascia along the anterolateral mesorectum. The lack of evident fasciae in fetal specimens suggested that these might be formed in later developmental stages.

Lymphatic drainage pathways from the cervix uteri: implications for radical hysterectomy?

OBJECTIVE

Radical hysterectomy with pelvic lymphadenectomy is the treatment of choice for early-stage cervical cancer. Wertheim's original technique has been often modified, mainly in the extent of parametrectomy. Okabayashi's technique is considered as the most radical variant regarding removal of the ventral parametrium and paracolpal tissues. Surgical outcome concerning recurrence and survival is good, but morbidity is high due to autonomic nerve damage. While the autonomic network has been studied extensively, the lymphatic system is less understood. This study describes the lymphatic drainage pathways of the cervix uteri and specifically the presence of lymphatics in the vesico-uterine ligament (VUL).

METHODS

A developmental series of 10 human female fetal pelves was studied. Paraffin embedded blocks were sliced in transverse sections of 8 or 10 μm. Analysis was performed by staining with antibodies against LYVE-1 (lymphatic endothelium), S100 (Schwann cells), alpha-Smooth Muscle Actin (smooth muscle cells) and CD68 (macrophages). The results were three-dimensionally represented.

RESULTS

Two major pathways drained the cervix uteri: a supra-ureteral pathway, running in the cardinal ligament superior to the ureter, and a dorsal pathway, running in the utero-sacral ligament towards the rectal pillars. No lymph vessels draining the cervix uteri were detected in the VUL. In the paracolpal parametrium lymph vessels draining the upper vagina fused with those from the bladder.

CONCLUSIONS

The VUL does not contain lymphatics from the cervix uteri. Hence, the favorable survival outcomes of the Okabayashi technique cannot be explained by radical removal of lymphatic pathways in the ventrocaudal parametrium.