Transanal endoscopic microsurgery (TEM) is an advanced surgical technique for transanal excision (TAE) for early rectal cancer or benign rectal lesions.¹ It was introduced to overcome the drawback of conventional transanal excision such as the ease in securing the surgical field and reducing collision between instruments,^2,3 and several studies showed TEM provided better surgical and oncological outcomes than conventional TAE.^4-6 Despite superior outcomes of TEM in the literature, it has not been widely performed due to the complex learning curve, cost issue, specialized instrumentation and complication risks such as defective anorectal function after the surgery.^7,8

Transanal minimally invasive surgery (TAMIS) is an emerging surgical technique to be an improvement to TEM as it can provide spacious surgical field by making pneumorectum, shorter learning curve of operation due to the use the conventional laparoscopic devices and lower costs as a result.^9,10 In several studies, TAMIS has shown to be safe and effective for benign lesions and early-stage malignancy in the middle rectum.^11,12 In this study, we report our experience in the use of TAMIS and assess the feasibility and safety of this surgical technique in operating for various rectal diseases that require a transanal approach.

Study patients

Between 2013 and 2019, 30 patients underwent TAMIS for a rectal lesion at Seoul National University Boramae Medical Center. Selection criteria for TAMIS included early rectal cancers without lymph node involvement, lateral spreading tumours that comprised less than 50% of the circumference, neuroendocrine tumours (NET), and incomplete resected adenoma or NET after endoscopic submucosal dissection (ESD) or endoscopic mucosal resection (EMR). Other patients with rectal pathology such as rectal sinus, rectal stenosis and anastomosis dehiscence were also candidates for TAMIS.

The clinical data including age, gender, body mass index (BMI), tumour size, distance from the anal verge (AV), diagnosis, operation time, postoperative complications, duration of hospital stay, and post-operative pathological margin status were obtained retrospectively from the electronic medical records. The study protocol was approved by the institutional review board of Seoul National University Boramae Medical Center (IRB number, 16-2016-117).

Operative technique

The procedure was carried out in the order of ‘exposure’, ‘excision’ and ‘closure’. Patient was positioned in lithotomy position under general anasesthesia. Digital rectal examination with gentle anal dilatation prior to insertion of single-incision laparoscopic surgery port (SILS^TM port; Medtronic, UK) was done and then the port was anchored with 1-0 vicryl suture on right anterior, left anterior, and posterior side of the anal canal. Then pneumorectum was made by CO₂ gas inflation and maintained 18 mmHg pressure and we used 5 mm 30° laparoscope to reduce the collision between instruments and optimize the view during the surgery. The inflation pressure of 18 mmHg was decided with reference to previous study on the use of TAMIS on mid-rectal lesions.¹³

After the lesion is identified, it was grasped and lifted gently. The mucosa was marked by hook at least 0.5 cm away from lesion to achieve safety margin. Dissection was done from caudal to cranial approach and a Harmonic scalpel (Ethicon^®) was used to excise the rectal lesion down to mesorectal fat (Fig. 1). After complete detachment of proximal attachments, careful hemostasis and irrigation with normal saline were performed and the closure of the defect was accomplished by using ENDOLOOP^®.

Patients characteristics

Total of 30 patients (19 males and 11 females) were eligible for analysis. The analysis of patient characteristics is represented in Table 1. The mean age at surgery was 54.4±17.1 years and mean BMI was 24.3±3.1. The mean distance from the anal verge to the rectal lesion was 7.0±3.1 cm with a mean size of 1.6±1.6 cm. 14 patients (46.7%) underwent endoscopic resection prior to operation, of which 10 (71.4%) received EMR and 4 (28.6%) received ESD. Most of the patients had undergone TAMIS for NET (60%) followed by an adenoma (16.7%) and rectal cancer (13.3%). There were single cases of rectal stenosis, rectal sinus and anastomosis dehiscence after low anterior resection included in the study. The latter 3 cases were included as a candidate for TAMIS as the transanal approach of the surgery would be beneficial to the patients considering the nature, size and the location of the pathology.

Clinical outcomes

The operation related clinical outcome is represented in Table 2. The mean operation time was 52.1±33.5 minutes and the mean duration of hospital stay after surgery was 4.3±4.2 days. 4 patients (13.3%) had minor complications after TAMIS with 2 patients (50%) had complained of diarrhea, 1 patient (25%) complained of fecal incontinence. All patients recovered within 1 week after surgery without any specific treatment. 1 patient (25%) complained of uncomplicated fluid in the operation bed which subsided without further intervention. There was no dehiscence or stricture of the repair site in all patients.

We had 2 cases (6.7%) where the operation was converted to conventional TAE. One was converted due to long operation time of 190 minute caused by hypermotility of the rectum during to repair the resection site (Case 24). The other case was converted due to large lesion (7 cm) very close from the anal verge (2 cm) (Case 21), and this was the only case where the resection margin status was positive pathologically. From our experience TAMIS was suitable and effective in resecting lesions in various locations in the rectum but there were technical difficulties in operating on large lesions located very close to the anal verge. The detailed patient data is represented in Table 3.

Conventional TAE is difficult to adopt for mid to upper rectal lesion due to lack of proper visualization. On the other hand, TAMIS is a comfortable method to visualize the operative field by the use of videoscope through a pneumorectum. In our experience, TAMIS enabled operation on most length of the rectum (ranging from 2 to 15 cm from AV) apart from the anal verge. However, there were ergonomic difficulties the surgeon encounters when operating the low-lying rectal lesions because of the ‘fulcrum effect’¹⁴ where the shorter the distance between the end of a laparoscopic instrument and the port as the fulcrum point, the more force must be used. The excessive force will result in tissue tears. In particular, intracorporeal suturing and knot-tying for the resected site located within 5 cm of the anal verge were the most challenging but this could be dealt with by using ENDOLOOP^® ligatures or V-lock^® suture in our experience. Rimonda et al. showed that TAMIS failed to suture the rectal wall effectively in ex vivo setting.¹⁵ However, in our study laparoscopic dissection under a clear operating field using a videoscope in the pneumorectum allowed complete en bloc resection and this reduced specimen fragmentation rate and local recurrence rate.⁴ We experienced only one patient (Case 21) who had a large adenoma of 7 cm in diameter had an positive resection margin after TAMIS.

Overall mean operative time was 52.1±33.5 minutes. Considering reported TEM average operating times to range from 67 to 79 minutes,^16,17 our operative time with of TAMIS is shorter than that. Also, TAMIS is proposed to have a gentle learning curve than TEM which has a steep learning curve due to limited space within the proctoscope and the lack of triangulation.¹⁸

In one case (Case 24), it took 190 minutes caused by hypermotility of the rectum during the repair of the resection site. The main factor that prolonged operation was the bowel wall fluctuance and the hypermobility, which interfered with suturing further delaying the surgery. To prevent this situation, Daniel et al. reported the use of intravenous butylscopolamine administered before starting the surgery to reduce bowel spasms and gas-related fluctuation.

Only one patient complaint of fecal incontinence after TAMIS, although the duration of symptom was shorter than 1 week. In the literature, functional outcome data of TEM are inconsistent, but the quality of life after TAMIS indicated low severity of symptoms of anal incontinence.^19-21

TAMIS is not our routine practice for early rectal cancers due to the high risk of local recurrence. The postoperative local recurrence rate following local excision for pT1 rectal cancer is in the range of 4% to 24%, whereas the local recurrence following radical surgery is in the range of 0% to 7%.^22,23 Thus several institutions apply TAMIS in the treatment of well-selected stage I rectal cancer.^11,24 We considered TAMIS for early rectal cancer in 4 cases of which 2 cases (Case 24 & 27) was not suitable for a radical resection due to extensive past medical history.

Use of TAMIS in anastomosis leakage has not been studied in the literature but other transanal techniques such as TAE and TEM were used with successful repair of the dehiscence.^25,26 But the cases of anastomosis dehiscence that was repaired in the literature were dehiscence seen during the primary operation and thus would not have had the difficulty of dealing with hard fibrotic tissue present in the patient (Case 30) we operated on. Although TAMIS provides a good view and is capable of repairing such defect, precaution should be made by the operating surgeon when deciding whether the repair of dehiscence will be successful according to the nature of the tissue.

Most of our TAMIS cases were NET with or without endoscopic resection. The incidence of NETs of the colon and rectum has been increasing in the past decades, thought due to increased screening colonoscopies.²⁷ NET of the rectum that is ≤1 cm in size as well as well-differentiated with World Health Organization grade 1 has very good prognosis. Previous studies have suggested that primary tumour size is the strongest predictor of regional nodal metastasis.²⁸ The disease-free survival rate of 49 patients with rectal NET smaller than 1 cm in size is reported 96.2% at 53 months after local excision or ablation.²⁹ Today, 5-year survival for stage I rectal NETs with no angioinvasion that are <1 cm approach 100%.³⁰ There is even no need to follow-up for rectal NETs <1 cm by the NCCN guideline.³⁰ In this study, TAMIS proved to be a feasible and safe treatment option for rectal NET especially smaller than 1 cm without evidence of lymph node metastasis. Also, TAMIS was an option for further resection of the remnant lesion after an incomplete endoscopic procedure. A case of delayed local excision of rectal NET after hepatic resection for giant liver metastasis reported the patient has been disease-free for 2 years with good quality of life.³¹

Our study was limited by its retrospective nature, small sample size and short follow-up period. The retrospective design may have caused unintended selection bias of tumors particularly suited for TAMIS. Most of the lesions removed using TAMIS are NET in this study our result suggests that TAMIS may be safe and feasible for NET, but the oncological safety needs to be addressed with further studies. In conclusion, this study shows that the TAMIS is a useful method for local excision of rectal lesion located in mid to upper rectum as well as other rectal pathologies that require the transanal approach. The main strength of TAMIS is the ability to provide a clear visualization of the operating field when compared to other transanal approach techniques especially in the mid to upper rectum, and thus is a safe and feasible option of treatment of rectal pathologies in various locations of the rectum.

RS is the guarantor of the content of the manuscript, contributed substantially to the study design, data analysis and interpretation, and the writing of the manuscript. MKK contributed substantially to the study design, data interpretation, and the writing of the first draft and subsequent revisions of the manuscript. BHS contributed to data analysis and interpretation. SCH contributed substantially to data analysis and interpretation, and the writing of the manuscript.

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