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Page 2 of 13 Jahansouz et al. Mini-invasive Surg 2021;5:1 I http://dx.doi.org/10.20517/2574-1225.2020.82

INTRODUCTION
Our understanding of rectal cancer is advancing at a rapid pace. Treatment options have expanded
requiring surgeons to be facile at not only traditional open surgery, but also minimally invasive techniques,
such as the laparoscopic and robotic platforms. Minimally invasive surgery techniques have been applied
not only to the intra-abdominal approach, but also transanal approach as well. Atallah, Albert and
Larach were the first to report this application in their seminal paper describing the approach of single-
[1]
port laparoscopy, coining the term transanal minimally invasive surgery (TAMIS) in 2009 . TAMIS was
established to serve as an alternative to transanal endoscopic microsurgery (TEM). Both TEM and TAMIS
[2]
demonstrate superior oncological results over traditional transanal excision (TAE) . While TEM is safe
and effective for the treatment of early rectal cancer, its widespread use has been hampered by its high cost
of specialized instrumentation and steep learning curve . TAMIS is a technique of single-port laparoscopy
[3,4]
enabling the use of widely used laparoscopic instruments with the access of TEM, with reduced cost and
[1,5]
possibly less trauma to the anal sphincter . The TEM platform offers improved access to higher lesions
with retraction of the rectal valves.

INDICATIONS FOR TAMIS
The indications for TAMIS have traditionally followed the same guidelines as for open transanal excision
[6]
of rectal tumors set forth by the National Comprehensive Cancer Network (NCCN) . Tumors should
be < 3 cm in size and encompass less than one-third of the circumference of the bowel lumen. However,
TAMIS overcomes many of these historical limitations of TAE by offering greater access to middle and
upper rectal lesions and improved visualization in a confined operating field. Lesion location is usually <
15 cm from the anal verge and because of the seating of the transanal platform (discussed below), tumors
less than 4 cm from the anal verge may require a hybrid approach with traditional TAE. Tumor pathology
must be favorable. Thus, benign disease (polyps without submucosal invasion or excisional biopsy for
masses of uncertain malignant potential) or uT1 malignant disease with favorable tumor characteristics (no
lymphovascular invasion, perineural invasion, or mucinous component) are appropriate . TAMIS also
[7,8]
has a role in local excision following incomplete polypectomy to provide negative margins, as well as in
cases of palliative resection in patients who are unfit for total mesorectal excision (TME) . The quality of
[9]
[10]
local excision appears to be equally achieved as that by TEM . Following excision, if any high-risk features
are identified, such as sm3 invasion, lymphovascular invasion, or positive margins, further treatment is
[11]
recommended . Notably, no negative effects are seen on oncologic outcomes for subsequent radical
[12]
resection .

OPERATIVE OVERVIEW
TAMIS is traditionally performed under general anesthesia, but spinal anesthesia has also been
described [13–16] . Advocates for spinal anesthesia have suggested that this modality offers more stable
pneumorectum due to improved rectal wall relaxation . Once the transanal port is inserted and
[14]
pneumorectum is established, the lesion is identified, and a 0.5-1.0 cm margin is marked circumferentially
using electrocautery. Either full thickness or submucosal dissection ensues. Once excised, the specimen is
oriented and sent to pathology. Pneumorectum is reestablished under slightly reduced pressure to allow for
closure of the defect . Should there be inadvertent intraperitoneal entry, standard laparoscopic abdominal
[17]
access can then be established with ports placed to assist with retraction for excision of the specimen as
well as closure of the defect [1,17] . It has also been shown that the defect may be left open, in the absence of
[18]
peritoneal entry, and it is generally done if a tension-free repair is not deemed possible . However, if left
open, there may be an increased risk of postoperative bleeding [19,20] . Although an increased risk of infection
may also be a concern with an open defect, this has not been conclusively shown [18–20] .