Introduction

As for surgical tumour management in general, the principal for radical rectal cancer surgery is removal of the primary tumour, including the regional lymphatics and prevention of tumour cell spillage (Table 1). Even after several decades of evaluation and research, controversy still exists as regards the extent of lymphadenectomy, the importance of the no-touch principle, the optimal free distal margin and the irrigation/washout of the rectal stump.

Although there may be surgeons today who apply Turnbull's "no-touch technique" [1], it is doubtful if it is of any major benefit [2]. Moreover, while for some surgeons 'wide lymphatic excision' means a "high tie" of the inferior mesenteric artery with inclusion of mesenteric lymphadenectomy, to others it means complete retroperitoneal clearance of all lymphatic tissue - i.e., pre-aortic as well as precaval lymph nodes ("pre-aortic strip"). Such a procedure enables removal of additional lymphatic tissue, but whether this confers an advantage in survival is unproven. Extended lateral internal iliac lymph node excision has been on trial in many series but there are no randomised clinical trials supporting its value. Proximal nodal involvement at the level of the inferior mesenteric artery, these nodes may indicate a high likelihood of systemic spread and then a low possibility of cure, regardless of the extent of surgery. Moreover, the price paid for such an extended surgery is a high incidence of urinary and sexual complications owing to autonomic nerve damage.

For the radical excision of a rectal cancer, a gener-

Table 1. Controversial issues in rectal cancer surgery "No-touch" technique?

Proximal clearance - "High tie/'pre-aortic' strip"? Distal clearance - "a 2- or 5-cm rule"? Lateral clearance - extensive lymph node dissection? Total mesorectal excision (TME)? Circumferential radial margin (CRM)?

ous distal free margin below the tumor has been an important issue. The well known "5-cm rule" was based on careful pathological investigations of the intramural tumour spread [3]. The measure was put into practice during the 1960s and was applied for a long time by most colorectal surgeons. However subsequent studies have shown evidence that intramural spread only occasionally exceeds 1-2 cm and that further increase of the distal margin beyond 2 cm does not improve the locoregional recurrence rate or survival [4]. It has been an established principle that the mesorectum and the wall of the rectum should be transected at the same level.

In contrast to many of these unconvincing attempts and doubtful results mentioned to improve radicality in rectal cancer surgery, the introduction of "the new surgical technique" - total mesorectal excision (TME) - presented by Heald et al. [5], has proved to be extremely effective, particularly by reducing intrapelvic recurrences. The technique has made a considerable impact on rectal cancer treatment worldwide. Heald's concept of the operation was based on the evidence of isolated metastases within the mesorectum distal to the primary tumour (Fig. 1) [6, 7]. The removal of the distal mesorectal tongue was considered to be the main secret of success. Although the incidence and location of the retrograde tumour extension into the mesorectum was seriously questioned, TME rapidly became the "gold standard" technique worldwide for anterior resection of the rectum and a marked reduction of local recurrence rates has been presented from many colorectal centres having adopted this technique (Table 2) [8-10].

Heald's TME procedure involved a meticulous sharp dissection of the entire mesorectum with the aim of removing tumour that had locally spread even via other mesorectal lymphatics. The plane of dissection extends along the avascular areolar plane outside the perirectal fascia - "the holy plane". As the sharp dissection is continued downwards, the ano-rectal ring is reached eventually, at which point the lowest part of the mesorectum is dissected free with removal of the distal "mesorectal tongue". The use of

Fig. 1. Total mesorec-tal excision (TME) according to Heald, 1982 [5]

Fig. 1. Total mesorec-tal excision (TME) according to Heald, 1982 [5]

Table 2. The locoregional recurrence rate at 4 years

Authors

Conventional

TME

technique (%)

technique (%)

Arbman et al. [8]

23

8

Havenga et al. [9]

32

9

Wibe et al. [11]

12

6

sharp dissection to develop the "holy plane" rather than blunt finger dissection was emphasised by Heald as a particularly important measure thought to lessen the risk of rupturing or tearing the mesorectal fascia, thus spreading tumour cells. Apart from total excision of the mesorectum, the procedure includes a radical proximal lymphatic excision performed by ligation of the inferior mesenteric artery 1 cm off the aorta and ligation of the inferior mesenteric vein 1 cm from the splenic vein but without an extra mesenteric 'pre-aortic strip'.

Heald's paper on the technique was criticised and the favourable results questioned, and the introduction of the TME principle started an intense debate with revival of interest in the details in pelvic anatomy and its curative value and indications for its use [10, 12-14].

In the original paper Heald stated that the main problem leading to high local recurrence rates in many studies was that isolated metastases within the mesorectum distal to the primary tumour were left behind. The article was interpreted as recommending removal of the entire mesorectum in all rectal cancer cases, regardless of the level of the rectal cancer. This statement has been seriously questioned however. The removal of the distal mesorectal tongue could not possibly be the sole explanation for the improved results, because recurrences develop frequently even after total abdominoperineal rectal excision in which all mesorectum is removed and the results in many other studies on rectal excision for cancer had demonstrated comparable local pelvic recurrence rates without taking out the entire mesorectum. Moreover, although mesorectal deposits can occur well distal to the tumour, the prevalence is considered too low to justify excision of the whole mesorectum to the level of the levator ani. The consequences would be a great number of ultralow anterior resections being done unnecessarily for tumours even in the upper third of the rectum, putting the patient at increased risk of anastomotic leakage and poor function [15]. Subsequently, the removal of the distal mesenteric tongue has been considered excessive as a standard procedure being indicated preferentially for low sited tumours. Therefore - in its present properly defined form - TME is recommended for distal mid- and lower rectal cancer, with complete excision of the visceral mesorectal tissue down to the level of the levators (Fig. 2, left panel), whereas for upper third or rectosigmoidal cancer a tumour-specific mesorectal excision (TSME) should be preferred, which means a precisely perpendicular and circumferential excision of the mesorectum to the level of an appropriate resection margin distal to the tumour (mostly 5 cm recommended) (Fig. 2, right panel).

The anatomical basis for the TME principle is certainly not new. It was very carefully defined by Jon-nesco [16] and Bissett et al. [13], putting emphasis on

MESOHECTUM

MESORECTUM

MESOHECTUM

MESORECTUM

About 2-5 cm below tumor

Total Mesorectal Excision (TME)

Tumour Specific Mesorectal Excision (TSME)

About 2-5 cm below tumor

Total Mesorectal Excision (TME)

Tumour Specific Mesorectal Excision (TSME)

Fig. 2. TME reserved for low tumours and TSME for more prox. tumours

Fig. 3. The importance of keeping the circumferential radial margin (CRM) clear. Local recurrence may result from an incomplete radial resection rather than from an incomplete distal mesorectal excision

the fact that mesorectum is enveloped in a thin fascia, and that violating the fascia may compromise radi-cality, increasing the rate of local recurrence [17-19]. The description of the fascia propria plane also emphasises the importance of an adequate circumferential margin (Fig. 3) and it may well be that the main value of the TME procedure may be attributed to the ability to keep this margin clear. Local recurrence may result from an incomplete radial resection, although the surgeon may not always be capable of knowing whether this margin is clear of disease. It has been demonstrated that about 25% of cases may have unsuspected involvement of the radial margin after rectal excision. And leaving residual disease at the cut radial margin would mean that recurrence is inevitable. TME has been shown to decrease the rate of positive radial margins and this may be one of its main impacts on prevention of local recurrence [20-22].

Local recurrence may result from an incomplete radial resection rather than from an incomplete distal mesorectal excision. Heald changed the emphasis

Fig. 4. The rude, blind and blunt dissection technique as it is often illustrated in traditional textbooks

subsequently from the extent of distal dissection or radial dissection to minimising the transection of perirectal lymphatics by keeping the fascial envelope intact.

The recent literature has in many respects been very confusing and unfortunate on this issue. Heald may not have discovered a superior unrecognised technique and his results may well be questioned, but it is beyond dispute that his contribution has been extremely important. He has defined more clearly than most others exactly what he is doing and in a way that others can readily duplicate. It is reasonable to assume that the dramatic reduction in local recurrence that has been recently reported from many surgical units may simply reflect the poor effectiveness of surgical technique employed prior to the introduction and training of the TME technique. Although scientifically unproven, there is strong evidence to show that the sharp dissection under full visualisation - preferably aided by means of a head lamp - is superior to a blunt and partly blind dissection technique, and should be very important to avoid ploughing into the wrong dissection plane. Judging by the illustrations shown, even in well known recently published textbooks, the blunt dissection technique seems to be quite common even in expert hands (Fig. 4).

The TME technique has to be rigorously tested in a prospective, randomised trial to throw light on these issues.

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