Endoscopic submucosal dissection (ESD) is an endoscopic technique that allows the removal of lesions of the gastrointestinal tract. The European Society of Gastrointestinal Endoscopy (ESGE) suggests to consider ESD for the removal of colorectal lesions that cannot be removed enbloc with standard polypectomy or endoscopic mucosal resection (EMR) and for lesions that are > 20 mm in diameter, with a high probability of having a limited submucosal invasion.

ESD is a technically difficult and time-consuming procedure that is very difficult to learn and to perform, but it allows higher enbloc resection rates compared to other endoscopic techniques and is less invasive than surgery requiring less length of hospital stay.

Recently, several new techniques and devices have been developed to facilitate ESD and to overcome difficulties related to challenging situations. The main difficulties are related to the instability of the operating field, due to the physiologic peristalsis, and to the loss of traction, due to the single operating channel.

Tissue Retraction System (TRS, Boston scientific) is a new endoscopic platform, that consists of an expandable and dynamically-controlled intra-luminal chamber, mounted on a flexible overtube, and two associated specifically designed retractor graspers. The system is front-loaded over the colonoscope and introduced into the colon. When the target area is reached, the retractor system is deployed creating an expanded, optimally reconfigured and stable operating field around the target lesion. Then endoscopic removal of the lesion is performed using available endoscopic instruments (injection needles, knives, snares, etc) through the operating channel of the colonoscope with assistance of two retractor graspers. Each accessory within the TRS can be moved forward and backward, left or right, rotated 360 degrees, and can be advanced out and pulled in, regardless of the TRS.

The investigators hypothesize that the TRS can improve visualization of lesions and stabilize the work environment by allowing retraction and tissue resection during ESD.

TRS is a new device not yet commercially available, thus no study has been already performed in humans to evaluate its feasibility and safety to speed up the ESD of left colon and rectum lesions.

The investigator's proposal is to perform a pilot study to evaluate the feasibility, the efficacy and the safety in patients undergoing ESD of colorectal lesions with the assistance of the TRS.

Inclusion Criteria:

• left colon and rectal lesions matching the criteria of ESD removal: depressed/flat elevated morphology and irregular or nongranular surface pattern, larger than 20 mm; lesions that cannot be optimally and radically removed with standard polypectomy or EMR
• age ≥18 years
• ability to sign the informed consent

Exclusion Criteria:

• deep submucosal invasion diagnosed by distorted pit (Kudo's type V) and/or capillary (Sano's type III) patterns [5];
• poor general condition (American Society of Anesthesiologists score ≥ 3);
• coagulation disorders;
• pregnancy and breastfeeding;
• inability to sign the informed consent.