AIM To investigated the usefulness of a novel slim type balltipped Flush Knife (Flush Knife-BTS) over ball-tipped Flush Knife (Flush Knife-BT) in functional experiments and clinical practice.METHODS In order to evaluate the functionality of Flush KnifeBTS, water aspiration speed, resistance to knife insertion through the scope, and waterjet flushing speed were compared between Flush Knife-BTS and BT. In clinical practice, esophageal endoscopic submucosal dissection (ESD) performed using Flush Knife-BTS or BT by an experienced endoscopist between October 2015 and January 2016 were retrospectively reviewed. The treatment speed and frequency of removing and reinserting the knife to aspirate fluid and air during ESD sessions were analyzed.RESULTS Functional experiments revealed that water aspiration speed by the endoscope equipped with a 2.8-mm working channel with Flush Knife-BTS was 7.7-fold faster than that with conventional Flush Knife-BT. Resistance to knife insertion inside the scope with a 2.8-mm working channel was reduced by 40% with FlushK nife-BTS. The waterjet flushing speed was faster with the use of Flush Knife-BT. In clinical practice, a comparison of 6 and 7 ESD using Flush Knife-BT and BTS, respectively, revealed that the median treatment speed was 25.5 mm2/min (range 19.6-30.3) in the BT group and 44.2 mm2/min(range 15.5-55.4) in the BTS group (P = 0.0633). However, the median treatment speed was significantly faster with Flush Knife-BTS when the resection size was larger than 1000 m2(n = 4, median 24.2 mm2/min, range 19.6-27.7 vs n = 4, median 47.4 mm2/min, range 44.2-55.4, P = 0.0209). The frequency of knife replacement was less in the BTS group (median 1.76 times in one hour, range 0-5.45) than in the BT group (7.02 times in one hour, range 4.23-15)(P = 0.0065).CONCLUSION Our results indicate that FlushK nife-BTS enhances the performance of ESD, particularly for large lesions, by improving air and fluid aspiration and knife insertion during ESD and reducing the frequency of knife removal and reinsertion. AIM To investigate the usefulness of a novel slim type balltipped Flush Knife (Flush Knife-BTS) over ball-tipped Flush Knife (Flush Knife-BT) in functional experiments and clinical practice. METHODS In order to evaluate the functionality of Flush Knife BTS, water In clinical practice, esophageal endoscopic submucosal dissection (ESD) performed using Flush Knife-BTS or BT by an experienced endoscopist between October 2015 and January 2016 were retrospectively reviewed. The treatment speed and frequency of removing and reinserting the knife to aspirate fluid and air during ESD sessions were analyzed. RESULTS Functional experiments revealed that water aspiration speed by the endoscope equipped with a 2.8-mm working channel with Flush Knife-BTS was 7.7-fold faster than that with conventional Flush Knife-BT. Resistance to knife insertion inside the scope The waterjet flushing speed was faster with the use of Flush Knife-BT. In clinical practice, a comparison of 6 and 7 ESD using Flush Knife-BT and BTS, respectively, revealed that the median treatment speed was 25.5 mm2 / min (range 19.6-30.3) in the BT group and 44.2 mm2 / min (range 15.5-55.4) in the BTS group (P = 0.0633). However, the median treatment speed was significantly faster with Flush Knife-BTS when the resection size was larger than 1000 m2 (n = 4, median 24.2 mm2 / min, range 19.6-27.7 vs n = 4, median 47.4 mm2 / min, range 44.2-55.4, P = 0.0209). The frequency of knife replacement was less in the BTS group (median 1.76 times in one hour, range 0-5.45) than in the BT group (7.02 times in one hour, range 4.23-15) (P = 0.0065 ). CONCLUSION Our results indicate that FlushK nife-BTS enhances the performance of ESD, particularly for large lesions, by improving air and fluid aspiration and knife insertion during ESD andreducing the frequency of knife removal and reinsertion.