SILS TEM: The new armamentarium in transanal endoscopic surgery.

Despite the wide adoption of sphincter saving surgery, still 10–30% of patients end up with colostomy and 30–40% of them might suffer urinary and sexual dysfunction.[1] The concept of transanal endoscopic microsurgery (TEM) was developed to facilitate endoscopic full-thickness excision of mid to high rectal lesions not amenable to standard colonoscopic or transanal resection thus avoiding conventional open or laparoscopic surgery.

However, several factors have limited widespread use of TEM, including the initial cost of the equipment, the need for the specialised instrumentation and steep learning curve. Moreover, faecal incontinence is a concern after TEM as surgery is performed through a 40 mm rigid proctoscope, which requires anal dilatation prior to insertion.[1]

There is increasing number of publications on the use of single incision laparoscopic surgery (SILS) ports to perform TEM and this led to the development of the concept of SILS TEM. Apart from standard laparoscopic instruments, no specialised equipment is required. Moreover, SILS TEM does not entail any additional skills from surgeons trained in abdominal SILS. SILS TEM has several advantages as access to the rectum is gained through smaller diameter (30 mm) soft port with no need for prior anal dilatation. The use of articulating instruments that can permit a wider range of movements and a 5 mm laparoscope, which gives further working space.[2]

For SILS TEM to become the new standard in TEM it needs to address several challenges: the technique should be safe and cost effective, it should have a reasonable learning curve, the skills the surgeon would gain during training for SILS TEM should be transferable to new and expected developments in colorectal surgery and SILS TEM should ideally be able to embrace emerging new indications in rectal surgery.

TEM is known to have highly safe profile with morbidity rate ranging from 3% to 7% and a mortality rate of 0.01%.[3] Therefore, SILS TEM should have a similar, if not better, safety profile as the technique facilitates accurate identification of the margins of mucosal abnormality in the distended rectum which in turn leads to reduced risk of margin positivity. The high-quality magnified image allows for a more accurate dissection technique with better haemostasis.[4] SILS TEM will prove to be unequivocally cost-effective as it requires no special instruments and its minimally invasive nature will be reflected in reduced hospital stay. The only additional cost of SILS TEM is the cost of accesses port. Since the procedure resembles normal laparoscopy and basic laparoscopic instruments are used, the technique should be easier to adopt and master for an experienced endoscopic surgeon.

The optimal approach for surgical resection of small benign and malignant rectal lesions is yet to be found as all the current approaches have their own limitations.[5] There are several new techniques and approaches under investigations such as natural orifice transluminal endoscopic surgery (NOTES), totally transrectal endoscopic total mesorectal excision[6] and robotic transanal minimally invasive surgery (TAMIS).[7] Skills acquired in SILS TEM will be easily transferable to those techniques.

The TEM approach is used primarily for local excision of selected low, middle and upper benign rectal tumours. TEM as a solitary procedure is not considered an oncologically adequate treatment for rectal cancer. Traditionally, TEM is offered for highly selected group of rectal cancer patients (tumour size <3 cm and T1 with no adverse histological features) as the local recurrence rate in this sub-group is <4% with oncological outcomes similar to those of radical surgery, yet with reduced mortality, morbidity and better quality of life. However, a growing number of authors report using TEM for resection of small rectal cancers, although this indication remains highly controversial.[8]

Currently, there is growing interest in rectum-preservation strategies for patients who have a good clinical response to neoadjuvant treatment and even for some locally advanced rectal cancer given the encouraging long-term results of patients with complete pathological response after chemoradiotherapy. Currently, two controlled randomised trials (CRTs) are examining this. The CARTS study (chemoradiation therapy for rectal cancer in the distal rectum followed by organ-sparing transanal endoscopic microsurgery) has been designed to assess the adequacy of TEM following pre-operative radiotherapy. Patients with a clinical T1-3 N0 M0 rectal adenocarcinoma below 10 cm from the anal verge will receive neoadjuvant chemoradiation therapy followed by TEM 8–10 weeks later. The UK-TREC trial (TEM and Radiotherapy in Early Rectal Cancer) is offered for patients with early rectal cancer (T1-2N0) where patients are randomised between radical TME surgery and short-course preoperative radiotherapy with delayed local excision at 8–10 weeks. If local recurrence rate in these studies were found to be acceptable or comparable to standard TME surgery then SILS TEM might become the standard treatment of rectal cancer in the future.

The indications for TEM are expanding to include resection of neuroendocrine tumours or tumours of extramucosal origin (e.g. leiomyomas) as they carry no nodal threat, retrorectal cysts, masses within the rectovaginal septum, transanal strictureplasty, for transanal pelvic abscess drainage, rectal foreign body removal and also to obtain mucosal closure after placement of the plug in high transsphincteric anal fistula.[8] SILS TEM can potentially be used for all these indications.

CONCLUSION

Although SILS TEM may address many of the difficulties and shortcomings associated with traditional TEM, this new technique is not without its own limitations. SILS TEM is still very early in its development. Eventually, additional experience with the technique and advancements in instrumentation will be essential at expanding its usefulness.[4] The time spent in the learning curve of SILS TEM is justified as the skills gained would be transferable to the newly emerging minimally invasive approaches to rectal surgery.