BACKGROUND: Curvilinear array ultrasound transducers enable tissue sampling and have therapeutic capabilities. Nevertheless, colonic intubation and maneuvering with these transducers is technically challenging and is therefore typically limited to the rectosigmoid area. This retrospective cohort study aimed to evaluate the safety, feasibility, and diagnostic yield of colonoscopic ultrasound-guided fine-needle aspiration in deep colonic intubation. IMPACT OF INNOVATION: The impact of this innovation is to enable tissue sampling of colonic and extracolonic lesions guided by endoscopic ultrasound. TECHNOLOGY, MATERIALS, AND METHODS: Curvilinear array ultrasound is used in the evaluation of luminal and extraluminal colonic diseases. Thirteen patients underwent colonoscopic ultrasound with a curvilinear array ultrasound endoscope in a single center for subepithelial lesions, cancer staging, and extracolonic lesions from July 2015 to February 2021. Endosonography was performed using an Olympus EU-ME1 and GF-UCT 180 with a 5-12MHz curvilinear array transducer. The primary outcome was the percentage of patients who were successfully scanned with the endoscopic ultrasound. The secondary outcomes included the success rate of fine-needle aspiration, the diagnostic yield of the tissue samples, and the adverse events related to the procedure. PRELIMINARY RESULTS: A total of 13 female patients underwent colonoscopic ultrasound. All patients (100%, 13/13) were successfully scanned. Fine-needle aspiration was deemed necessary and successfully performed in 100% (5/5) of the patients. Tissue samples collected by fine-needle aspiration resulted in a diagnostic yield of 60%, and no adverse events resulted from this intervention. CONCLUSIONS: This study demonstrates the feasibility of performing colonoscopic ultrasound with a curvilinear array transducer. Fine-needle aspiration for subepithelial, colonic, and extracolonic lesions is feasible and safe in this setting with no adverse events reported in our study. FUTURE DIRECTIONS: Future research should be directed toward validating colonoscopic ultrasound with a curvilinear array transducer technique in prospective randomized trials. Studies evaluating the feasibility and safety of endoscopic ultrasound-guided interventions in the colon, such as abscess drainage and enteral anastomosis, should be considered.