Transanal Mesorectal Excision: The New Challenge in Rectal Cancer.

total mesorectal excision (tme) performed by an open approach is the standard technique for the surgical treatment of rectal cancer. surgical treatment of rectal cancer has significantly evolved during the last decade, with improved pelvic imaging, optimizing neoadjuvant therapy, and the minimally invasive “revolution” of laparoscopic surgery. the main objectives of surgery are completeness of the mesorectum, sphincter preservation, and pelvic nerve preservation. Regardless of whether an open or laparoscopic approach is used, the most pressing current challenges relate to achieving these objectives in low lesions. Robotic tme has been advocated as an alternative to conventional laparoscopic tme, but large studies supporting the efficacy of robotic tme are scarce. on the other hand, the transanal tme (tatme) has recently been introduced with the aim of providing an elegant solution to address these surgical issues. since the first human case of tatme was reported in 2010, hundreds of cases have been published, called notes-tme, tamis-tme, down-to-up tme, or laparoscopic tatme. although the technique may differ between surgeons, the common objective is to perform a partial or total dissection of the mesorectum via the transanal route. this strategy may improve the distal mesorectal dissection, which is the most technically challenging part by a transabdominal (open or laparoscopic) approach. the original article from Kanso et al takes on part of this new challenge. Conceptually, tatme includes 2 different concepts, the partial and the total tatme. the partial tatme (open tatme) dissects only the distal part of the rectum, and the objective is to facilitate a sphincter-sparing surgery and to avoid conversion in difficult distal tumors. it is mostly performed with conventional anal retractors under direct vision. the total tatme (laparoscopic tatme) dissects the whole mesorectum with the aim to improve the oncologic quality of surgery and to avoid pelvic nerve injury. it is performed with laparoscopic instruments, and the potential indications are midrectal and low rectal cancers. a different concept is natural orifice transluminal endoscopic surgery tme, which includes a total tatme with ligation of the inferior mesenteric artery and splenic flexure mobilization with endoscopic instruments. this last option is not standardized; the procedure is often hybrid, and the objective is only technical, by avoiding the abdominal ports. What is the rationale to develop a tatme? the abdominal dissection of the distal part of the rectum is difficult because of the limitation to expose the surgical field and the plan of dissection. these difficulties can result in “coning in” on the mesorectal specimen, with accompanying loss of the adequate circumferential resection margin. although the laparoscopic approach offers the advantage of a broader view of the deep pelvis, the risk of coning in remains because of the limitations of long straight instruments, difficulties in providing an adequate traction and countertraction in this tight space, and limited angulation of stapling devices. the presence of genital organs in men worsens this difficulty. inadequate exposure and loss of the good plane of dissection also induces the risk to create severe pelvic bleeding or autonomic nerve injuries. finally, these technical difficulties increase the rate of conversion in a high-risk group, such as a narrow male pelvis or an obese patient with bulky mesorectum. the low rectal dissection during the abdominal approach (open or laparoscopic) is probably the part of the tme that is not well adapted to the anatomy of the distal rectum. What are the advantages of the tatme? the transanal view, whether in combination with Co 2 insufflation, offers a better visualization of the distal rectum, facilitating the understanding of the anatomic and embryological planes of dissection. the absence of the small bowel and the fact that the rectum is pushed and not retracted are other factors improving the precision of the dissection. the technical feasibility of a radical sphincter-sparing laparoscopic surgery even in unfavorable anatomical and tumor characteristics, such as men with fixed, anterior, or recurrent low rectal cancer, has been reported. Kanso et al report their experience in this Journal using a partial tatme performed with conventional retractors under direct vision. the objective was to compare the results of a partial tatme with those of the abdominal tme in Transanal Mesorectal Excision: The New Challenge in Rectal Cancer