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Page 2 of 12 De Rosa et al. Mini-invasive Surg 2020;4:34 I http://dx.doi.org/10.20517/2574-1225.2019.53

surgery, demonstrating how the integrity of the mesorectal envelope is paramount in achieving excellent
[2]
oncological outcomes in terms of local recurrence . Minimally invasive techniques have shown major
benefits in the treatment of colon cancer, but rectal surgery is technically more demanding and the
associated steep learning curve has made the laparoscopic approach less appealing.

Nevertheless, surgical techniques are constantly evolving and searching for less invasive approaches,
particularly pursuing the principles of natural orifice transluminal endoscopic surgery (NOTES) represents
an exciting goal. A further reduction in postoperative pain, less wound infections and hernias, better
cosmetic results and a shorter time off work are the key advantages of these super-minimally invasive
[3,4]
approaches .
[5]
It is suggested that bulky colorectal specimens can be effectively excised transanally and several
experimental studies have demonstrated the safety and feasibility of rectosigmoid transanal resection in
[6,7]
animal and cadaveric models .

Pure NOTES still requires significant improvement in instruments and technology to make the transition
to the clinical arena and remains largely an experimental approach, while hybrid procedures such as
natural orifice specimen extraction (NOSE) techniques combined with laparoscopy can reduce the impact
of surgery further [5,7,8] .

As a result of these experiences, the first transanal rectal resection with a hybrid approach was described by
[7]
Sylla et al. in a 76-year-old lady with a rectal cancer located at 8 cm from anal verge.
This first report, describing transanal TME (TaTME), aroused great interest because it demonstrated the
feasibility of a hybrid NOTES procedure that could be applied to challenging real-life situations, such as the
difficult TME for mid and distal rectal cancer.

Indeed, even in the hands of experts, rectal cancer surgery in obese, male patients with bulky, distal tumors
can be extremely difficult, where the ballooning of rectum into the sacral concavity creates a sharp angle
[9]
with the anal canal . In these cases, difficulty in staying in the correct dissection plane can easily result in
[10]
an incomplete specimen with possible inadequate circumferential resection margin (CRM) .

Despite the standardization of technique for TME, several studies have demonstrated that the quality of the
final specimen is important in predicting cancer-related outcomes [11,12] . Obese patients with low, anteriorly-
located tumors, those treated with neo-adjuvant chemoradiotherapy, or those with a narrow pelvis are at
particular risk of incomplete mesorectal excision [13-15] .

Laparoscopy offers the advantage of improved visualization of deep pelvic structures, but the limitations
imposed by long and straight instruments, particularly applying traction and counter-traction maneuvers
in a narrow space, remain significant challenges. In addition, laparoscopic stapling technology has proved
rather inadequate and difficult to use low in the pelvis, increasing the risk of poor outcomes [16,17] .

TaTME was conceived and developed with the aim of overcoming these specific limitations, particularly
in mid and low cancers. The closer, more detailed view of the pelvic structures makes the dissections from
below more accurate and effective, leading to a better specimen. Inserting the purse-string below the tumor
allows the surgeon to accurately control the distal resection margin (DRM). In the case of anterior tumors,
with a high risk of an involved circumferential margin, the transanal approach can facilitate the dissection
of Denonvilliers fascia, thus minimizing the risk of injuries to prostate, seminal vesicles, and the nerves of
the inferior hypogastric plexus and nervi erigentes.