Conceptually TME has its basis in embryology.The original hypothesis was that cancer spreadwill tend, initially at least, to remain within theembryologic lymphovascular hindgut "envelope"the mesorectum and mesocolon. The corollary to the perfect specimen and cure isthe perfect preservation of the layers surrounding

the mesorectum which, are formed by the autonomicnerves and plexuses. The first obstacle is that few real-istic photographs, sketches or diagrams have been pu-blished and visualisation and lighting low down in thepelvis is always problematic. Even when they are un-derstood and visualised the difficulties inherent in pre-serving these nerves are due to the fact that they areactually adherent to the mesorectum at certain pointswhere the dissection becomes particularly challenging.The most important and most adherent areas are theso-called "lateral ligaments" – low down laterally andanterolaterally where the inferior hypogastric plexuses(virtually the pelvic sex-brain) tether the whole meso-rectal package. When the specimen has been carefullyreleased it lifts up in a somewhat spectacular fashion –hence the old idea that there are ligaments at these po-ints. A lesser degree of adherence may be found at va-rious other points and particular care is required ante-riorly where the nerves are converging towards thebulb of the penis with a trapezoidal septum betweenthem – Denonvillier’s "fascia"- which is in turn adher-ent to the anterior mesorectum and lower down in theprostate.

Key words: nerve, preservation, rectal cancer

STEPS OF THE OPERATION

The key principle is that dissection should only proceedin the areolar tissue plane (the "holy plane") within

(and thus sparing) the autonomic nerve plexuses. Alsooutside the hind gut and therefore best preserved are thenonvisceral presacral fat pad (when present), the parietal

sidewall fascia of the small pelvis, the vesicles, and theprostate in the male, and the vagina in the female. All ofthe dissection should be performed sharp with diathermyor scissors under direct vision with good light. Moderndiathermy improvements such as "Triverse" and "ForceTriad" (Valleylab) provide more precise dissection withminimum collateral damage and probable reduction in co-agulation damage to the nerves.

Throughout, dedicated assistants should provide three-directional traction and counter-traction to open up theplanes for the operator—diathermy can only be used sa-fely when the areolar tissue is on stretch. Compared withtraditional methods of manual extraction, the difference intime can be considerable. A careful TME plus pouch toanus reconstruction with careful nerve preservation takes3 to 5 hours according to the detail of the patient’s buildand the particular cancer; a conventional APE was oftencompleted in 1 hour. "The devil is in the detail".

"Starting right"—the pedicle package—the clue to thetop of the "holy plane"

Starting correctly involves three-directional traction be-tween the mesocolon and retroperitoneum to identify theplane between the back of the pedicle package and the go-nadal vessels, ureter, and preaortic sympathetic nerves—all of which must be carefully preserved.

The key to this phase is the recognition of the shiny fas-cial-covered surface of the back of the pedicle—like a ta-pering longitudinal "sausage" with the inferior mesentericvessels within and their origins at the upper end. Thismust be gently lifted forward to open up precisely the keyembryological plane. It is usual in open surgery to start onthe left of the sigmoid mesocolon.

It is equally satisfactory, as commonly performed in la-paroscopic surgery, to start on the right. If all this is donecarefully a plexus of autonomic nerves including two pre-aortic mini-trunks splitting around the artery can be visu-alised and preserved. (Fig.1)

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Autonomic nerve preservation in rectal cancer surgery–The Forgotten Part of the TME message a Practical"Workshop" Description for Surgeons

B. HealdThe Pelican Cancer Centre, Basingstoke, UK

/STRU^NI RAD UDK 616.351-006.04-089

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High Ligation of the Inferior Mesenteric Vessels (Figs.2and 3).With the pedicle package lifted gently forward thedissection behind it can be extended up to its proximalend; separate high ligations of the inferior mesenteric ar-tery and vein can be performed with the pedicle controlledby the left index finger. The artery is taken 1 to 2 cm ante-rior to the aorta so as to spare the sympathetic nerve ple-xuses; (Fig.1) the vein is divided above its last tributaryclose to the pancreas.

These two high ligations are an integral part of the oth-erwise avascular dissection, which needs to be developedupward extensively for a full mobilization of the splenicflexure if anastomosis low in the pelvis is planned. ForAPE the high ligation of the artery alone is required andthe vein can be taken nearby.

The "Division of Convenience"

The sigmoid mesentery and the sigmoid colon are divi-ded well above the cancer. This is an important step inevery cancer dissection as optimal mobility of the top ofthe specimen facilitates gentle opening of the perimeso-rectal planes by traction and countertraction in any direc-tion throughout the pelvic dissection – important for nervepreservation.

High Posterior Dissection

Forward traction demonstrates the shiny posterior sur-face of mesorectum within the bifurcation of the superiorhypogastric plexus (Fig. 4). Recognition of this shiny fas-cial covering may precede the actual nerve identification.This plane is extended gradually downward toward andeventually beyond the tip of the coccyx, step by step asother sectors of the circumference are developed. Verylong St. Marks or

Reverse curve (Heald) St. Marks retractors (Bolton Sur-gical, Sheffield) are really crucial.

Lateral Pelvic Dissection

This involves forward extension of the plane around tothe sides, gently easing the adherent hypogastric nerveslaterally off the mesorectal surface under direct vision(Fig. 5 and 6). The freedom to lift the divided rectosig-moid forward often means that the tangentially runninghypogastric nerves are first positively identified at thisstage, the superior hypogastric plexus itself only becom-ing obvious proximal to the nerves after the areolar tissueplane has been dissected away from the shiny mesorectalsurface on each side.

These nerves are far more important than hitherto appre-ciated because they subserve many of the functions of or-gasm in both sexes, while the inferior, more distal inferiorhypogastric plexus must be preserved to protect the moreobvious and substantial parasympathetic function of erec-tion.

The Nervi Erigentes or "Erigent Pillars” (Fig. 7)formposteroanterior lateral "pillars" on the pelvic sidewall. Ca-daver dissections have led us all to be taught that the pel-vic parasympathetic outflow is tripartite S2–3–4. How-

ever, to the surgeon there is no doubt that a recognizablelandmark is often a single or bifid "pillar" comprising anerve root arising from the front of the S3 component ofthe main sacral plexus (Fig, which is out of sight posteri-orly). Possibly, the pillar-like appearance is in part due tothe forcible forward traction on the prostate and bladderapplied in order to see during an open operation, and this

FIGURE 1

FIGURE 2

FIGURE 3

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tends to bow the nerves medially and thus make themstand out so that they are more readily identified than inlaparoscopic surgery.

This retraction does not occur to the same extent in a la-paroscopic operation, which may account for the reportedhigher incidence of nerve damage. These pillars and thehypogastric plexuses curve medially (Fig. 8) toward theback of the prostate, where they form the neurovascularbundles, which taper toward the urethra at the apex of theprostate. Here they become the erectile nerves of the cor-pora cavernosa. The pillars or roots arise outside the pa-rietal fascia that they penetrate obliquely as they curve to-wards the point of adherence to the anterolateral aspect ofthe mesorectum.

More anteriorally the holy plane is followed downwardtoward the vesicle laterally, with the expanding plexiformband of inferior hypogastric plexus behind but increas-ingly adherent to it. In essence, there is no actual ligamentbut an area of adherence between mesorectum mediallyand plexus laterally which tethers the rectum and meso-rectum to the lateral wall at this critically important point:small branches of nerves and vessels penetrate throughbut none generally reaches more than 1 to 2 mm in diame-ter.

The key nerves entering and forming this flattened bandfrom above are largely the sympathetic hypogastric nervescurving distally from the superior plexuses. From behindthe "erigent" parasympathetic nerves come forward to itfrom the anterior aspect of the sacral plexuses, which areout of sight. The "neural T junctions" are the nearest stru-ctures to "lateral ligaments" that the most careful surgeonswill find with precise dissection in the proper plane. Onlyrarely found by the surgeon during this dissection is the"middle rectal artery" (Fig. 9) which was, I believe, inpast days usually a surgical "mistake - being most often inreality a lateral intra mesorectal artery.

The so-called "stalk" that used to be divided usually rep-resented a "coning in" to the mesorectum and division ofan artery which should have been encapsulated by theperimesorectal block dissection. Such "coning in" does, ofcourse, imply a compromise of the oncological quality ofthe "block dissection" because it means that part of the di-stal mesorectum is being left in the pelvis.

The Anterior Dissection—Denonvilliers Septum

Dissection anterolaterally and anteriorly following thecorrect plane forward will, in the male, encompass the pe-ritoneal reflection that remains on the specimen and thusallows positive identification of the backs of the seminalvesicles. Forceful forward retraction on these with a St.Mark’s retractor will facilitate the development of the are-olar space between the vesicles and the smooth front ofthe mesorectal specimen (Fig. 10).

We call this smooth surface that is generally adherent toand clearly a part of the mesorectum Denonvilliers fasciaor the rectogenital septum. As one works distally, therecomes a point where this fascia must be divided trans-versely (Fig. 11) as it becomes adherent to the posteriorcapsule of the prostate. Particular care is necessary during

FIGURE 6

FIGURE 5

FIGURE 4

Br. 3 Autonomic nerve preservation in rectal cancer surgery 13

this step to avoid damage to the neurovascular bundles (ofWalsh) that constitute the distal condensation of the infe-rior hypogastric plexuses.

These are gradually intertwining with vessels to becomethe "neurovascular bundles of Walsh" which run postero-lateral to the prostate. These various steps all complementeach other – circumferentially, first in one segment andthen in another – usually furthest advanced at the back.Hand in hand with the anterior dissection goes the devel-opment of the lateral sidewall dissection, first on the right,then on the left and so on with great care and gentleness.

The whole area of the rectoprostatic interface is a par-ticular current challenge in technical surgery—both openand laparoscopic – especially because the neuro-vascularbundles posteriorly relative to the prostate (Fig. 12).

Dissection of the Most Distal Mesorectum

The anatomy of the insertion of the mesorectal "pack-age" into the pelvic floor becomes difficult for the surge-on to grasp because of its inaccessibility behind the ves-icles and prostate in the male and to a lesser extent behindthe vagina in the female. The situation is further compli-cated by the fact that the levators are like a "flower pot" incontinuity with external sphincter distally. Conceptually,and because of the distortion introduced by upward trac-tion, surgeons tend to think of the pelvic floor as beingmuch flatter than it really is in vivo, especially if an assis-tant applies upward pressure on the perineum.

If one doubts this, a careful look at the layers on a coro-nal MRI scan will make it evident. A clear three-dimen-sional perception of the now globular bilobed mesorectumin the depth of the pelvis and the surrounding neural la-mella is the most elusive and challenging conceptual ac-quisition for the aspiring rectal cancer surgeon.

Partial Mesorectal Excision (i.e., High AnteriorResection and Mesorectal Transection)

While muscle tube margin may safely be reduced to 1cm in the interest of anal conservation, we have alwaysbelieved that, if less than a total mesorectal excision is co-ntemplated, a minimum of 5 cm of mesorectum distal tothe lower edge of the cancer must be dissected in the pe-rimesorectal plane. If, therefore, after initial mobilizationthere is a clear 5 cm of mesorectum, then tapering into themesentery, in the interest of making a more minor opera-tion and a higher anastomosis, becomes acceptable.

The operation then becomes perimesorectal mobiliza-tion, mesorectal transection, anterior resection, and pri-mary anastomosis for rectal cancers above around 12 cm.The absolute rule for all rectal cancers is that either 5 cmof mesorectum distal to the tumor or the whole mesorec-tum must be removed intact with the same preoccupationto achieve clear circumferential margins. The higher anas-tomosis and the reduction of risk to the nerves combinesto make the PME operation significantly less major forthe patient, and a temporary stoma may often be avoidedin these higher tumours.

FIGURE 7

FIGURE 9

FIGURE 8

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Identification of the Neurovascular Bundles behind theprostate and bulb of penis – The prone jack-knife positionfor the perineal phase of Abdomino-Perineal Excision(APE)

The author has been impressed in recent years by sev-eral advantages inherent in performing the perineal phaseof the abdomino-perineal operation, when that is indeednecessary for the very lowest tumours, in the face downposition. For the first time we have established that, if amarker clip is placed on the most distal component of theinferior hypogastric plexus towards the end of the ab-dominal phase, the downward path of these crucial nervescan be later identified from below. Success in this endeav-our appears to require the removal of the coccyx whichalso facilitates precision in all of this final phase. Aroundthe upper lateral (Fig. 13) corner of the prostate the nerveplexus becomes vascularised and intertwined with vessels,but does remain within a fascial sheath that

Courses down to become the nerve supply of the bulband body of the penis. We believe that the routine visual-isation of this lowest component of the nerve plexuses isone of the great challenges of the new century for the sur-geon striving for better nerve preservation.

It is probable that the greater incidence of impotence af-ter APE reflects the failure of most surgeons in the past torecognise these neurovascular bundles during the perinealphase.

CONCLUSION

Rectal cancer surgery is probably the most rewarding ofall the challenges to the aspiring gastrointestinal surgeon.Arguably there is no cancer operation where proper deci-sions, the judicious selective use of adjuvant therapy, and,most of all, surgical skill of the highest order can bring somuch benefit to the patient. Cancer cure, normality ofbowel function, avoidance of a lifelong stoma, sexual fun-ction—all of these hang in the balance for the patient. Theprofession still has a long way to go in using its resolvesto deliver what is possible and affordable to each personwho hopes for an optimal outcome – the preservation of

FIGURE 12

FIGURE 11

FIGURE 10 FIGURE 13

Br. 3 Autonomic nerve preservation in rectal cancer surgery 15

sexual function should have the highest priority in surgi-cal teaching in the immediate future.

SUMMARY

PREZERVACIJA AUTONOMNIH NERAVA U HIRUR-GIJI KARCINOMA REKTUMA- ZABORAVLJENI DEOTME

Konceptualno totalna mezorektalna ekscizija (TME) sebazira na embriologiji. Originalna hipoteza navodi da }ese karcinom inicijalno razvijati u okviru embriolo{kih gra-nica limfovaskularnog "omota~a" mezorektuma i mezok-olna.

Klju~ne re~i: nervi, prezervacija, karcinom rektuma

FURTHER READING:

1. McDonald PJ, Heald RJ.A survey of postoperativefunction after rectal anastomosis with circular stapling de-vices.Br J Surg. 1983 Dec; 70(12): 727-9

2.Murty M, Enker WE, Martz J. Current status of totalmesorectal excision and autonomic nerve preservation inrectal cancer. Semin Surg Oncol. 2000 Dec; 19(4):321-8.

3. Havenga K, Enker WE.utonomic nerve preserving to-tal mesorectal excision. Surg Clin North Am. 2002 Oct;82(5): 1009-18.

4. Mastery of Surgery, Volume 2, Chapter 140, Page1542, Rectal Cancer in the 21st Century – Radical Opera-tions: Anterior Resection and Abdominoperineal Exci-sion.

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