Novel Use of a Rigidizing Overtube for Endoscopic Ultrasound-Directed Sampling of a Sequel Subepithelial Lesion. Here are our disclosures. Subepithelial lesions of the gastrointestinal tract are often detected incidentally and occur in fewer than 1% of upper and lower endoscopies. Colonic subepithelial lesions proximal to the rectal sigmoid colon present unique diagnostic challenges as these cannot be accessed with a linear echo endoscope for tissue sampling. In such situations, options include through-the-scope ultrasound probe evaluation, surveillance cross-sectional imaging, or surgical resection, all of which possess significant shortcomings. Thus, additional modalities of tissue acquisition are needed to guide clinical decision making. In this video, we introduce an innovative application of the use of a rigidizing overtube in endoscopic ultrasound-guided biopsy of a sequel subepithelial lesion that obviates the need for these less desirable and often more invasive means of evaluation. A 71-year-old female with a history of hypertension presents to establish GI care and screening colon evaluation. She had no worrisome family history of GI malignancy. Her index screening colonoscopy revealed a submucosal lesion adjacent to the appendix approximately 1 centimeter in size endoscopically. Tunneling biopsies during this exam were non-diagnostic. To better characterize this finding, a contrast-enhanced CT scan of her abdomen and pelvis were obtained, which confirmed the presence of a 1.1-centimeter submucosal lesion adjacent to the appendix orifice. Endoscopic full-thickness resection as well as surgical consultation were offered but politely declined by the patient. A multidisciplinary discussion recommended further endoscopic surveillance. Repeat endoscopy with through-the-scope probe was performed and showed a 11-millimeter by 9-millimeter lesion located in layer 2. Through-the-scope ultrasound evaluation was limited due to difficult probe adherence to the target tissue. Multidisciplinary discussions recommended endoscopic surveillance, and one year later, she underwent repeat colonoscopy with linear endoscopic ultrasound facilitated by a rigidizing overtube. This is an example of a single-use flexible overtube. It is a flexible tube with varying internal diameters and lengths ranging from 85 centimeters to 110 centimeters. It has a port that attaches to a vacuum pump. With a twist of a handle, the air is removed from the lining of the overtube, which causes the overtube to instantly become rigid. The endoscopist can then toggle between a flexible and rigid state, depending on the clinical needs. In this video, the colonoscope has been advanced to the cecum, where the approximately 1-centimeter subepithelial parapendaceal lesion is seen. The overtube was advanced to the proximal colon and positioned immediately distal to the lesion of interest and was toggled to the rigid state. It was left in place and the colonoscope was withdrawn and exchanged for a linear EUS scope. Through the overtube, the EUS scope is advanced to the cecum and can be seen traversing the distal end of the overtube. With only gentle pressure on the EUS scope, it is brought into position and the lesion is brought into view. The lesion is visualized under ultrasound and appears to be a beautifully round hypoechoic and well-defined 11-millimeter by 9-millimeter lesion originating from layer 2, the deep mucosa. The endoscopist measurements are seen here and the arrow denotes the layer of origin. Actuations made from a Francine tip 22-gauge fine needle biopsy needle yielded a core tissue sample. The echo endoscope was withdrawn and the colonoscope was reinserted through the overtube with the ribbed distal end visualized of the 110-centimeter overtube with a 16-millimeter inner diameter. There was an immediate hematoma formation and further sampling was not pursued. There was no mucosal bleeding and the hematoma was self-limited. The procedure was technically successful and without clinically significant complication. Cytological examination of the specimen returned inflammatory fibroid lesion, negative for dysplasia, positive for actin-desmin, negative for CS117 and S100. As a result of the improved visualization afforded by the echo endoscope and EUS-directed sampling, the patient was able to confidently avoid more invasive endoscopic management or surgical intervention. This case is the first reported use of a rigidizing overtube for EUS-guided biopsy of a subepithelial sacral lesion, demonstrating its technical feasibility and potential to enhance our diagnostic accuracy for similar proximal colon subepithelial lesions. The rigidizing overtube can act as a conduit for the linear EUS scope to previously inaccessible areas of the GI tract, particularly the proximal colon. It is important to recognize this is a powerful application of a rigidizing overtube that creates the possibility of EUS-directed tissue sampling of proximal colon lesions, and one that has not been previously reported. The technique highlights its potential to achieve safe and effective minimally invasive tissue sampling and detailed assessment of the gut lumen layers in anatomically challenging areas. Evaluation of subepithelial lesions in the proximal colon is fraught with challenges and inadequate diagnostic and therapeutic devices, where EUS- directed fine needle biopsy was previously not feasible. The rigidizing overtube creates a conduit for safe access to the right colon using a linear echo endoscope. The described technique facilitated an EUS-directed fine needle biopsy of a parapendaceal subepithelial lesion and avoided the need for ongoing surveillance or surgical management. Novel utilization of existing endoscopic devices, such as the rigidizing overtube, enables a safe, effective, and minimally invasive management of difficult-to-reach subepithelial lesions. It is foreseeable that this technique could be expanded to additional therapeutic maneuvers, such as transluminal drainage of fluid collections. Thank you for listening.

rigidizing overtube

endoscopic ultrasound

subepithelial lesion

diagnostic tissue sampling

transluminal fluid drainage