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A new instrumental platform for Trans-Anal Submucosal Endoscopic Resection (TASER)
  1. Zacharias P Tsiamoulos1,
  2. Janindra Warusavitarne2,
  3. Omar Faiz2,
  4. Andrew Castello-Cortes3,
  5. Timothy Elliott1,
  6. Simon T Peake1,
  7. Paul Bassett4,
  8. Brian P Saunders1
  1. 1Wolfson Unit for Endoscopy, St Mark's Hospital/Academic Institute, London, UK
  2. 2Department of Colorectal Surgery, St Mark's Hospital/Academic Institute, London, UK
  3. 3Department of Anesthesia/ITU, St Mark's Hospital/Academic Institute, London, UK
  4. 4Statsconsultancy Ltd., Amersham, UK
  1. Correspondence to Dr Zacharias P Tsiamoulos, Wolfson Unit for Endoscopy, St Mark's Hospital/Academic Institute, Watford Road, London HA1 3UJ, UK; ztsiamoulos{at}

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Existing trans-anal approaches for complete excision of large and complex rectal polyps (CRPs) remain suboptimal due to technical complexity and inflexibility leading to the risk of inadequate excision and need for proctectomy, especially when using a single-channel flexible endoscope. Trans-Anal Submucosal Endoscopic Resection (TASER) provides a flexible endo-surgical platform with enhanced visualisation and therapeutic options delivered via an endoscope assisted by simultaneous, dynamic trans-anal retraction devices (Figure 1). Preliminary results in 17 patients with complex and very large (>5 cm) as well as recurrent polyps with severe submucosal fibrosis showed that the application of different endoscopic resection techniques was facilitated (Figure 2).

Figure 1

Instrumental triangulation created with one endoscope and two laparoscopic retractors using the GelPoint path device; real time, ‘dynamic’ retraction (lift) of the polyp with the aid of retracting laparoscopic forceps.

Figure 2

Complex rectal polyps (CRPs) (lower and mid rectal lesions) excised with Trans-Anal Submucosal Endoscopic Resection-endoscopic submucosal dissection (TASER-ESD) and TASER-ESD/EMR sessions (prior to the excision, post-polypectomy defect and follow-up scar free of recurrence).

In more detail

The new platform was employed in 17 consecutive patients (mean age 63 years, 10 men/7 women) between January 2013 and June 2014, referred with CRPs, in a single-centre, observational cohort study. Prior to referral, all patients had had previous failed attempts with conventional endoscopic techniques. TASER involved placing the GelPoint path (Applied Medical, USA) platform across the anus to facilitate three airtight rectal access ports; one to carry an endoscope to provide vision, gas insufflation and resection/haemostasic devices and two to pass laparoscopic instruments for tissue retraction, suturing, clipping or cutting. The purpose of this study was to evaluate the feasibility, technical success and safety profile of this new hybrid, endo-surgery approach for CRPs using different endoscopic techniques.

Eighteen TASER procedures (one patient required two sessions) were employed in these 17 patients on the 17 CRPs (mean size 88 mm/range, 50–180 mm). Complete excision was achieved in 16/17 patients (94%). The mean procedure time was 185 min/range, 65–480 min. TASER-aided endoscopic resection was performed using endoscopic submucosal dissection (ESD) in seven cases (38.9%), ESD+ Piecemeal-Endoscopic-Mucosal-Resection/P-EMR in 4/18 (22.2%), ESD+P-EMR+Endoscopic-Mucosal-Ablation/EMA in 3/18 (16.7%), ESD+Trans-Anal-Excision/TAE in 2/18 (11.1%) and ESD+P-EMR+EMA+TAE in 2/18 (11.1%). There were no inadvertent perforations and just one minor episode of delayed bleeding. One patient developed bacteraemia post-procedure requiring a 4-night hospital stay; remaining patients were discharged within 24 h. First follow-up colonoscopy showed 12/16 with no recurrence (75%), 4/16 (25%) with <15 mm polyp recurrence (easily treatable) and 8/16 (50%) with some luminal narrowing but no rectal stricturing.

Find more details on online supplementary methods and results.


The TASER concept has several predecessors: in colorectal surgical practice, Trans-anal Endoscopic Micro-Surgery (TEMS), with a dedicated rigid operating proctoscope, has become the standard minimally invasive option for treating large rectal lesions. Although there are significant setup costs, TEMS allows instrument ‘triangulation’ and the option for a full-thickness resection to optimise local staging. However, the TEMS platform is large, (4 cm diameter), rigid and has been associated with the risk of short-term incontinence and rectal stenosis after the resection of circumferential 'carpet' adenomas. (Smart C, et al. Best Pract Res Clin Gastroenterol 2014;28:143). Subtle, lateral margins of flat lower rectal CRPs may be difficult to define precisely with TEMS leading to concerns regarding the risk of incomplete resection and inevitable recurrence (Allaix ME, et al. Surg Endosc 2012;26:2594). Also, the TEMS resection instruments are relatively large, making precise dissection of the submucosal plain problematic, which may lead to full-thickness excisions (over treatment) for mucosal lesions, increasing the complication risk and duration of hospital stay (Bignell MB, et al. Colorectal Dis 2010;12:e99). Trans-anal minimally invasive surgery (TAMIS) has been the next step, employing technology borrowed from single access port abdominal surgery, and is less expensive and invasive than TEMS allowing multiport working through an a-traumatic soft flexible 3.6 cm access channel. TAMIS shares, however, the disadvantages of TEMS in terms of mucosal visualisation and imprecise submucosal dissection (Rimonda R, et al. Surg Endosc 2013;27:3762). eTAMIS then added the concept of improved visualisation with the aid of a flexible endoscope (McLemore EC, et al. Surg Endosc 2013;27:1842–5).

We have taken the eTAMIS concept several steps further by using the endoscope as the primary platform for visualisation, cutting, dissection, insufflation and haemostasis supported by dynamic tissue retraction with laparoscopic instruments passed through the remaining two trans-anal ports. This approach necessitates cooperative working between a laparoscopic surgeon and a therapeutic endoscopist, which incurs a logistic challenge and enhanced cost compared with existing endoscopic modalities. However, the possibility of a definitive, minimally invasive resection without recourse to expensive surgical options in our opinion more than justifies the cost. By bringing together the skills and equipment of the therapeutic endoscopist with those of the laparoscopic surgeon, an optimal resection strategy appears possible with minimal morbidity. Complications in our series were acceptably low with no inadvertent perforations. All episodes of intraprocedural bleeding were stopped promptly, even one episode of arterial bleeding which required a suture, and no patient required transfusion. In the light of an episode of bacteraemia post-TASER, we now routinely administer intravenous antibiotics for 24 h for any low rectal lesions where contamination and systemic bacterial spread are possible. The largest polyp in this series was 18 cm and was removed using a combination of all TASER modalities over two sessions and has resulted in eradication of the polyp without significant rectal narrowing. Most of this polyp was removed by submucosal dissection but where scarring and fibrosis were prominent a limited full-thickness excision was performed. We believe that by limiting the degree of thermal injury with very precise tissue dissection, confined predominantly within the submucosal plane, scarring and stenosis risk are minimised. In 1/17 (5.9%) patients, deep submucosal invasion was suspected during TASER and confirmed after subsequent curative surgery. Although this patient underwent a TASER procedure, his outcome was not compromised. Until now, all patients who have replied to our retrospective questionnaire on bowel function report high levels of satisfaction with the procedure. Recurrence rate is within endoscopic series, but comparisons may be difficult due to a possible selection of more difficult cases probably not well amenable to conventional endoscopic resection techniques.

In summary, this initial pilot case series has demonstrated the safety and effectiveness of the TASER concept for the minimally invasive treatment of CRPs previously destined for surgical resection. The approach is likely to develop further once new instruments are designed specifically for the platform and if our results are confirmed TASER could become the treatment of choice for previously difficult-to-treat large, CRPs.

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Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.


  • Competing interests None.

  • Provenance and peer review Not commissioned; internally peer reviewed.