BACKGROUND

Endoscopic submucosal dissection (ESD) is the standard treatment for large gastric and colorectal lesions with a high risk of intra-mucosal and superficial submucosal cancer ¹. However in western countries, there is no wide spread procedure due to the long learning curve (especially in colon) ², the high risk of adverse events and length of the procedure (an average of 54 to 116 minutes per procedure) ³. Hybrid ESD is a feasible alternative for the treatment of colorectal polyps. The procedure consists of an initial circumferential incision, followed by the resection of the remaining tissue with a snare ⁴. This procedure has several advantages, submucosal dissection is the most difficult step in ESD and with this method it is much easier. In addition, this technique is significantly quicker than the traditional procedure. However, retrospective non-randomized studies with Hybrid ESD have shown lower rates of en bloc resections than with ESD ^{4) (5}.

On the other hand, underwater endoscopic mucosal resection (UEMR) has been described as an alternative to endoscopic mucosal resection (EMR) without the performance of a submucosal cushion ⁶. This technique has recently shown amazing results, even in appendicular orifice and scarred polyps, with a low complication rate and a high en bloc resection rates compared to EMR ⁷. Therefore, the underwater strategy could help to overcome the technical disadvantages of hybrid ESD.

CASE REPORT

A 20 mm granular type lateral spreading tumor was found in the rectum, 3 cm from the dental line in the context of a colorectal cancer screening program, in a 71 year-old woman without any relevant medical history. Chromoendoscopy with Indigo carmine (0.5%) showed a regular Pit Pattern type IV lesion. Underwater hybrid ESD was performed after the patient had signed an informed consent. Firstly, a Splash-M Knife (Pentax Medical, Tokio, Japan) was used for the circumferential incision. Three hundred mL of saline was infused immediately until a complete lumen filling was achieved. The remaining tissue was easily snared using a 30-mm oval Captivator Snare (Boston Scientific, Costa Rica) without injecting any solution into the submucosal layer, due to the "floating effect" of the lesion submerged in saline. The resection was performed using an endocut Q current (effect 3, duration 1, interval 6) with an ERBE vio200 electrosurgical unit (ERBE, Tuebingen, Germany) (Fig. 1). The procedure was completed in 15 minutes without any adverse event. The resected specimen was sent to the pathology department and finally diagnosed as tubulovillous adenoma with high grade dysplasia, deep and lateral free margins. A follow up endoscopic assessment was performed three months after the procedure and there was no residual tissue or recurrent adenoma.

Fig. 1 Underwater hybrid ESD procedure: A-D. Initial steps of hybrid ESD (circumferential incision). E-F. Underwater Hybrid ESD resection phase. G. Submerged scar. H. Scar with rectal distension without saline. I. Extended specimen. 

DISCUSSION

Despite the theoretical advantages of hybrid ESD, the reported outcomes have been unsatisfactory, mainly due to the rates of en bloc resection compared to ESD (64% vs 87%) ⁴. The main reason for this is due to the difficulty to fit the snare into the oral edge of the lesions. Moreover, circumferential incision results in a loss of thickness in the submucosal layer due to the dispersion of injected fluid. For this reason, current trends in ESD avoid a complete circumferential incision and tricks are performed such as "the pocket-creation technique" during the initial steps ⁸. With regard to hybrid ESD, submucosal thickness is essential to grasp the polyp with a snare, as is the amount of non-dissected tissue. In recent randomized controlled trials, a non-dissected area of < 15 mm was required to achieve the goal of an en bloc resection. However, this issue implies a phase of "pure" submucosal dissection with the risk of adverse events in some cases ⁹. This undesirable likelihood could be avoided by using the underwater method, which has been shown to be safer than traditional EMR and also easier to perform ^{7) (10}.

In summary, in order to fill the gap between these different techniques, an underwater hybrid ESD was performed. The aim was to obtain an en bloc specimen, avoid complications and the long procedure time of ESD and also to overcome the technical disadvantages of hybrid ESD. The positive outcome in this case must be validated in more cases in order to assess its efficacy as an alternative to ESD.