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Page 4 of 9 Yap et al. Mini-invasive Surg 2019;3:3 I http://dx.doi.org/10.20517/2574-1225.2018.57

Figure 1. Transanal total mesorectal excision purse-string and proctectomy

full-thickness rectal wall incision performed with hook diathermy. Usually, the dissection is commenced
posteriorly as the plane between the presacral fascia and TME envelope is easiest to identify. An important
tip is that the rectum is usually pushed away to create more operating space, as opposed to laparoscopically
where the colon is usually pulled towards the operator. From this starting point, the dissection is then
performed circumferentially, with care taken not to continue in only one or two quadrants which would lead
to asymmetrical rectal retraction. Laterally, remaining close to the mesorectal fascia will reduce injury to
the pelvic sidewall and the nervi erigentes. Anteriorly, the dissection is in the rectovaginal plane or posterior
to Denonvilliers’ fascia in males. This dissection may be tailored depending on the position of the invasive
portion of the tumor, intentionally proceeding anterior to Denonvilliers’ fascia if necessary to secure a clear
margin. Another important note is that sometimes an “O” sign appears during dissection in the fatty tissue
[13]
[Figure 2]; this is an indication that an incorrect plane that is too lateral has been entered .

This dissection is then continued up towards the peritoneal reflection. Care must be taken to try and breach
the peritoneal cavity as late as possible, as once there is a connection between the two spaces, dissection
becomes more difficult due to the bellowing movement of mesorectum as pressures attempt to equalize.

The intraperitoneal dissection is completed either simultaneously or sequentially in the usual fashion
with splenic flexure mobilization and high ligation of the inferior mesenteric artery. The colon is either
exteriorized and transected through an abdominal incision, or if so desired, the specimen can be delivered
trans-anally with the assistance of a wound retractor by transecting the proximal margin laparoscopically
with a stapler. Care must be taken if a transanal extraction is attempted; the mesentery of the colon must be
divided to ensure that the marginal artery is torn.

A second purse-string is then placed with a 0 or 2/0 prolene in the distal cut end, while an anvil of a
circular stapler is secured to the proximal colon. A 19F Blakes drain is then cut to approximately 10 cm and
placed on the end of the anvil to facilitate transanal retrieval. Once this is accomplished, the purse-string
then being secured around the anvil. The stapler is then engaged and fired in the standard fashion. Other
techniques for a stapled end-to-end anastomosis have been described as well as techniques for other types of
anastomoses including: hand-sewn coloanal anastomosis and side-to-end stapled anastomosis [14,15] .

Although urethral injury is an oft-commented point raised in regards to TaTME, it mainly a concern where
the starting point of the dissection is intersphincteric or extremely close to the anorectal ring. Here, as
[16]
discussed in simulation by Kneist et al. , the perineal body is the only structure that protects this area and
separates these structures from the rectum. This is due to the fact that the prostate must be mobilized from