Endoscopic submucosal dissection, transanal endoscopic microsurgical submucosal dissection, and transanal minimally invasive surgery in rectal lesions

Abstract

The management of rectal lesions has been significantly enhanced by advancements in endoscopic and minimally invasive surgical techniques. Endoscopic submucosal dissection (ESD), transanal endoscopic microsurgical submucosal dissection (TEM-ESD), and transanal minimally invasive surgery (TAMIS) offer precision and reduced morbidity for treating these conditions. This minireview evaluates the efficacy, safety, and clinical outcomes of ESD, TEM-ESD, and TAMIS, highlighting their roles in the contemporary management of rectal lesions. A desktop research study with a particular focus on ESD, TEM-ESD, and TAMIS for rectal lesions was conducted. Key outcomes assessed include complete resection rates, complication rates, recurrence rates, and functional outcomes following the procedure. ESD is noted for its high rate of en bloc resection with minimal invasiveness, suitable for large or flat lesions. TEM-ESD has demonstrated similar efficacy, with additional benefits including shorter procedure times and a more favorable learning curve, compared to traditional ESD, as evidenced by recent comparative studies. TAMIS offers a less invasive option with enhanced visualization and accessibility, supporting its use in a broader range of rectal lesion cases. ESD, TEM-ESD, and TAMIS are all effective therapeutic options for rectal lesions, each presenting unique advantages depending on lesion characteristics and patient factors.

Key Words: Endoscopic submucosal dissection; Transanal endoscopic microsurgical submucosal dissection; Transanal minimally invasive surgery; Rectal adenomas; Early rectal cancer; Minimally invasive colorectal surgery; En bloc resection; Local excision techniques

Core Tip: Minimally invasive en bloc resection techniques have revolutionized the management of large rectal lesions, especially non-pedunculated polyps and early rectal cancers. This minireview compares three major approaches, namely, endoscopic submucosal dissection (ESD), transanal endoscopic microsurgical submucosal dissection (TEM-ESD), and transanal minimally invasive surgery (TAMIS), in terms of efficacy, safety, and technical feasibility. While ESD and TEM-ESD offer high en bloc resection rates with low recurrence, TAMIS is gaining popularity for its ergonomic advantages and ease of use. The minireview provides a critical perspective on indications, limitations, and future innovations, guiding clinicians in selecting the most appropriate technique based on lesion characteristics and institutional expertise.

INTRODUCTION

Colorectal cancer (CRC) is one of the most common malignancies worldwide and represents a significant public health burden due to its high incidence and mortality rates[1]. Among the precancerous conditions, rectal adenomas hold a pivotal role, given their potential for malignant transformation if not adequately managed. Early detection and removal of such lesions have been shown to substantially reduce CRC-related mortality[2].

Traditional endoscopic techniques, such as endoscopic mucosal resection (EMR), are frequently employed for excising rectal adenomas. However, limitations in achieving en bloc resection, especially in lesions larger than 2 cm or those with non-lifting characteristics, have raised concerns regarding incomplete resection and local recurrence[3]. Endoscopic submucosal dissection (ESD) has emerged as a superior alternative in terms of en bloc resection and oncological clearance[1,4], yet its steep learning curve, prolonged procedure time, and risk of complications have restricted its widespread use, particularly in Western countries[5].

To overcome the limitations of conventional methods, transanal endoscopic microsurgical submucosal dissection (TEM-ESD) has been developed. This hybrid technique combines the precise dissection advantages of ESD with the stable access and visualization features provided by TEM, especially in the challenging anatomy of the rectum[1,6]. TEM-ESD facilitates the complete excision of large or sessile rectal lesions while maintaining low morbidity and acceptable complication rates[3,7]. In this context, “giant lesions” are defined as rectal lesions larger than 3 cm, consistent with recent literature.

Evidence from systematic reviews and meta-analyses confirms the efficacy of TEM-ESD, showing high complete resection rates and favorable short-term outcomes compared to either ESD or standard TEM alone[1,5]. Moreover, transanal minimally invasive surgery (TAMIS), which shares several technical similarities with TEM, has also been demonstrated to be effective in excising rectal lesions, especially when tailored to individual patient and lesion characteristics[8].

Despite ongoing debates regarding long-term oncological outcomes, current data support the role of TEM-ESD in highly selected cases of rectal adenomas, particularly in specialized centers with appropriate expertise and infrastructure[4,9]. Guidelines and expert consensus recommend individualized treatment planning, aiming for complete excision, sphincter preservation, and minimal morbidity[2,10].

This minireview compares three emerging techniques for rectal lesion resection-ESD, TEM-ESD, and TAMIS-focusing on efficacy, safety, and clinical outcomes, to support evidence-based selection in clinical practice.

ESD

ESD is a technique that enables the removal of lesions limited to the submucosa in one piece using specialized cutting devices. The procedure consists of several stages: (1) First, the lesion to be dissected must be determined chromoendoscopically; (2) Following the marking of the determined border, an appropriate fluid injection must be made into the submucosa; and (3) The next stage is the dissection of the submucosa under the tumor after combining the area surrounding the marked borders with a preliminary incision (Figure 1)[11,12].

Figure 1 Sequential steps of endoscopic submucosal dissection for an early-stage colorectal lesion. A: Submucosal injection is performed to lift the lesion from the muscularis propria; B: Circumferential mucosal incision is initiated around the lesion; C: Submucosal dissection is carried out using an endoscopic knife; D: Hemostasis is achieved with coagulation forceps; E: Resected early-stage colorectal lesion after complete submucosal dissection.

ESD has some advantages and disadvantages compared to endoscopic mucosal resection (EMR). In addition to the benefits of being able to remove lesions larger than two centimeters in one piece, lesions that cannot be elevated with submucosal injection and recurrent lesions, the size and shape of the lesion to be removed can be done in a controlled manner, and even lesions with ulcers can be safely removed. It has disadvantages such as requiring more time and support personnel, and carrying a higher risk of bleeding and perforation[13].

ESD was initially developed for en bloc resection of large gastric lesions (> 2 cm), and subsequently extended to esophageal and colorectal neoplasms, as outlined in recent European Society of Gastrointestinal Endoscopy and Japan Gastroenterological Endoscopy Society guidelines[14]. ESD procedure of the colorectal region is technically more complex compared to the stomach. However, ESD is used in large lesions in the colorectal region, especially in tumors with lateral spread[15].

In the chromoendoscopic evaluation, Kashida et al[16] revealed a 2.4% submucosal cancer rate in lesions showing type IV pit pattern characteristics. Some studies have histologically confirmed the status of invasiveness or non-invasiveness using colonic pit pattern analysis[17]. In another study evaluating invasion into the submucosa, it was possible to estimate the depth of invasion and the presence of carcinoma with a rate of approximately 89% using detailed pit pattern analysis with chromo-magnified colonoscopy[18]. It has been reported that the depth of invasion in colonic lesions can be determined with 88% accuracy using endoscopic ultrasound; however, other studies have reported rates ranging from 37% to 66%[19].

It is essential to recall the standard procedural steps involved in colorectal ESD. These include: (1) Careful assessment and delineation of the lesion margins using chromoendoscopy; and (2) Followed by submucosal injection to lift the lesion away from the muscularis propria. A circumferential mucosal incision is then made around the marked area, and submucosal dissection is performed using electrosurgical knives. Hemostasis of any bleeding vessels is achieved throughout the procedure, and finally, the en bloc specimen is retrieved for pathological evaluation. Recently, traction-assisted techniques such as the multi-loop traction device (MLTD) have been developed to overcome visualization and access challenges during colorectal ESD. In a multicenter randomized controlled trial involving 108 patients, the MLTD group demonstrated a significantly higher technical success rate compared to conventional ESD (96.2% vs 71.0%; P = 0.0005), although the overall dissection speed did not significantly differ. Notably, expert endoscopists achieved faster dissection speeds when using MLTD (median: 21.6 mm²/minute vs 14.4 mm²/minute; P = 0.009), supporting its potential benefit in advanced hands[20]. The pocket-creation method (PCM) is an advanced ESD technique particularly effective for large sessile colorectal tumors with severe submucosal fibrosis or muscle-retracting (MR) sign. By creating a stable submucosal pocket under the lesion, PCM provides traction and allows for precise dissection along the muscularis layer. In a retrospective study comparing PCM to conventional ESD reported significantly shorter dissection times (median: 53.5 minutes vs 63 minutes; P = 0.036), faster dissection speed (19.3 mm²/minute vs 15.9 mm²/minute; P = 0.020), and a higher rate of pathologically negative vertical margins (98% vs 82%; P = 0.038). These advantages were especially notable in tumors with MR sign, where PCM achieved a 100% en bloc resection rate and superior histologic margins, even for deeply invasive submucosal carcinomas[21]. Another emerging technique is underwater ESD (UESD), where the lumen is filled with water instead of gas before dissection. This creates a buoyant effect on the mucosal flap and enhances visualization of the submucosal layer. A prospective randomized trial comparing UESD and conventional ESD for 20-50 mm laterally spreading colorectal tumors found that UESD had significantly shorter procedure time (49.5 ± 20.3 minutes vs 75.7 ± 36.1 minutes) and faster dissection speed (21.9 ± 6.9 mm²/minute vs 15.2 ± 7.3 mm²/minute), while maintaining comparable en bloc resection, R0 resection, and adverse event rates[22]. Robotic technology is increasingly being explored to overcome the limitations of conventional ESD, particularly the lack of direct tissue traction and the technical complexity of dissection. Robotic-assisted ESD and full-thickness excision have demonstrated potential to reduce procedure time and improve complete resection rates, especially in laterally spreading rectal tumors. When deep margins are unclear, robotic systems enable conversion to full-thickness resection in a controlled and safe manner. Although current gains over TEM are modest, ongoing development of longer and more flexible robotic systems is expected to expand robotic ESD applications to the left colon and beyond[23].

Despite these technical advancements, the learning curve for colorectal ESD remains steep, and the availability of structured training programs and experienced centers continues to be limited, particularly in Western countries.

TEM-ESD

Surgeons can now perform en bloc resections of larger lesions throughout the entire rectum, thanks to the introduction of TEM in the 1980s. The majority of specialists prefer full-thickness resection because it provides the best resection margins for potentially cancerous lesions. Still, it also jeopardizes the mesorectum and raises the risk of local problems. More recently, another technique for the en bloc removal of large colorectal adenomas was put forth: ESD, which was first described in Japan for the treatment of early gastric cancer[24].

A novel resection method, called TEM-ESD, combines the least invasive ESD method with the technological benefits of rigid TEM tools (Figure 2). Low morbidity and local recurrence rates have been associated with the beneficial use of this technique in treating low-risk carcinomas and rectal adenomas[25]. The main characteristic of this technique is the use of traction through a separately operated grasper during the submucosal dissection. Its benefits are further demonstrated when resecting complex lesions, such as giant tumors and tumors in challenging locations.

Figure 2 Steps of transanal endoscopic microsurgery-assisted endoscopic submucosal dissection for a rectal lesion. A: Endoscopic view of the nodular lesion; B: Submucosal dissection is initiated (black arrow); C: Muscularis propria layer is preserved during dissection (black arrow); D: Post-dissection view showing the complete resection site with intact muscularis propria; E: Resected lesion pinned on a board for pathological assessment.

The optimal method for the problematic local excision of large rectal adenomas and early adenocarcinomas has not yet been established. Most authors define giant rectal lesions as those with a maximal diameter exceeding 5 cm. En bloc excision of these lesions, primarily with TEM and more recently with ESD, has been the subject of very few research[26]. These trials demonstrated the viability of such techniques. Still, they also highlighted the high risk of tissue fragmentation and adverse outcomes, as well as the procedure's high degree of technical difficulty[27]. Many of these lesions are still referred for drastic surgical therapy, such as abdominoperineal resection or anterior resection with total mesorectal excision, most likely for this reason[28].

Although the technique's low recurrence rates and minimally invasive method make it extremely promising, one of its primary technical drawbacks is believed to be its limited traction. To date, none of the traction techniques and tools proposed to facilitate access to the submucosal plane have been widely adopted[29]. Large lesions may hinder visibility during the procedure, leading to prolonged surgical time and potentially preventing its completion. By using a second, independently controlled, stiff tool to provide traction during submucosal dissection, TEM-ESD solves this problem. This invention accelerates the overall process by simplifying viewing and dissection. The capacity of TEM-ESD to achieve high en bloc resection rates is another crucial characteristic. Given that an en bloc resection was feasible in every instance in our investigation, this characteristic also appears to apply to large lesions. The literature has frequently emphasized the significance of en bloc excision of rectal adenomas and its clear correlation with low recurrence rates. Furthermore, the research indicates that the probability of occult invasive carcinoma is significantly increased in big rectal adenomas, reaching 20% for lesions larger than 50 mm[30].

For big rectal adenomas and early adenocarcinomas, TEM-ESD seems to be a safe and practical therapy choice. These challenging lesions can be resected quickly and precisely with traction and triangulation, resulting in high en bloc resection rates. Periprocedural morbidity does not appear to be increased by the size of the lesions, and endoscopic treatment is an option for uncommon long-term adverse effects such as strictures. Most significantly, for both adenomas and low-risk adenocarcinomas, TEM-ESD provides outstanding long-term results with minimal recurrence rates[31].

TEM

TEM is a surgical method used in the treatment of rectal tumors. Professor Gerhard Buess developed this method in the 1980s[32]. TEM is used in the treatment of rectal polyps, carcinoid tumors, rectal prolapse, early-stage carcinomas, and selected rectal cancers (Figure 3)[7]. This method allows patients to reduce postoperative pain, recover more quickly, and return to their daily lives earlier. TEM has some limitations, so it should only be performed by trained and experienced surgeons. TEM can be used in cases of rectal polyps that are not suitable for colonoscopic resection or in cases of suspicious carcinomas with positive excision margins detected incidentally following polypectomy[33].

Figure 3 Transanal endoscopic microsurgery procedure for a rectal lesion. A: Circumferential marking around the lesion (white arrow); B: Incision of the muscular layer during full-thickness excision (white arrow); C: Post-resection defect following full-thickness excision (white arrow); D: Appearance of the rectal wall after defect closure with sutures (white arrow); E: Gross specimen of the resected lesion pinned for pathological evaluation.

TEM has also been used in the treatment of anastomotic strictures, the correction of rectal prolapse, and the excision of retrorectal tumors. Contraindications to TEM include poorly differentiated tumors with ulcers, extension to the muscularis propria, lymphovascular invasion, lymph node metastasis, or metastasis to distant organs. It is essential to perform accurate preoperative staging in patients undergoing TEM Methods such as digital examination, endorectal ultrasonography (ERUS), computed tomography, and magnetic resonance imaging can be used for this staging. TEM is an effective method in the treatment of rectal tumors and provides successful results in appropriate patients[15].

Accurate staging plays a pivotal role in selecting the optimal technique for local excision. High-resolution magnetic resonance imaging offers excellent assessment of mesorectal involvement and is preferred for evaluating advanced or deeply invasive lesions. Conversely, ERUS provides superior resolution in early-stage lesions and is particularly effective in distinguishing T1 from T2 tumors. Therefore, imaging modality selection can influence whether ESD, TEM-ESD, or TAMIS is the most appropriate intervention[34].

TAMIS has gained widespread interest due to its technical feasibility, reduced equipment cost compared to rigid platforms like TEM, and its adaptability in diverse hospital settings. It uses conventional laparoscopic instruments within a transanal access port, allowing for en bloc excision of rectal lesions with favorable perioperative outcomes. Studies have reported en bloc resection rates of 80%-95% for benign and early-stage malignant lesions, with low morbidity and preservation of anorectal function. TAMIS is also associated with a shorter learning curve compared to TEM and ESD, and its setup is more ergonomically favorable for surgeons. These attributes make TAMIS especially suitable for institutions with limited access to advanced endoscopic platforms, offering a cost-effective alternative for local excision in early rectal neoplasia (Table 1)[8,26,35].

Table 1 Comparative summary.

Feature	ESD	Transanal endoscopic microsurgical submucosal dissection	Transanal minimally invasive surgery
En bloc resection rate	High (> 85%)	Very high (> 90%)	Moderate (60%-80%)
Procedure time	Long	Moderate	Short
Learning curve	Steep	Moderate (faster than ESD)	Gentle
Morbidity	Perforation risk (approximately 5%-10%)	Low (due to traction and access)	Low
Use in large lesions	Effective, technically complex	Particularly suited for > 5 cm lesions	Limited by exposure/size
Access platform	Flexible endoscope	Rigid proctoscope (Buess platform)	Flexible single-port device
Sphincter preservation	Yes	Yes	Yes
Long-term outcomes	Excellent	Excellent	Good

ESD: Endoscopic submucosal dissection.

CONCLUSION

The increasing prevalence of laparoscopic colectomy techniques and the limited palpation capabilities of tumor-bearing segments have increased the importance of intraoperative methods, such as colonoscopy, to evaluate the proximal colon. In the management of rectal lesions, ESD and TEM-ESD have demonstrated favorable short-term outcomes and low recurrence rates. TAMIS, while offering comparable effectiveness, may provide enhanced patient comfort and faster recovery. All three techniques show promise in managing rectal neoplasms with low morbidity and high success rates. However, their integration into clinical practice requires a nuanced understanding of technique-specific indications, complication profiles, and appropriate patient selection. Further prospective and comparative studies are warranted to refine selection criteria based on lesion size, anatomical location, and institutional surgical expertise, ultimately guiding individualized treatment strategies.