Isolated gastric varices are usually located at the fundus or the cardia and fundus, which develop independently as part of a large portosystemic shunt that runs through the stomach wall, draining into the left renal vein or IVC (1) (Figure 1). Because of the large size and high-flow shunt, endoscopic treatment of isolated gastric varices is often difficult. According to recent development in interventional techniques, majority of isolated gastric varices can be successfully treated by balloon-occluded retrograde transvenous obliteration (B-RTO) technique (2-4). In B-RTO, sclerosant is injected via a balloon catheter positioned at the draining vein from the gastric varices (gastrorenal or gastrocaval shunt), and it fills and stagnates in the varices under balloon occlusion of the shunt. When the sclerosant sufficiently stagnates in the varices, complete thrombosis of the varices can be promised. Degree of the collateral venous drainages is one of the most important factors for successful procedure. Gastric varices without collateral drainage veins can be easily treated by the standard B-RTO technique because sclerosant infused via the balloon catheter can fill and stagnate in the varices (Figure 2). Some modification techniques of occlusion of collateral drainage veins with coils and/or balloons must be required for the treatment of gastric varices with abundant drainage veins (Figure 3). Coil embolization has been performed for devascularization of these collateral veins. However, this technique often required large number of coils and prolonged procedure times. Furthermore, uncatheterizable collateral veins may still remain after embolization in some cases. The technique of selective injection of sclerosant with advancing the balloon catheter beyond the collateral veins into the variceal drainage vein would be a useful technique for such cases (5). However, it is often difficult to advance the balloon catheter safely through the tortuous shunt. Recently, we devised a new coaxial balloon catheter system to be more easily advanced proximally to the varices beyond the outlet of the collateral veins (6). In this study, we evaluate the efficacy of the new coaxial balloon catheter system for treatment of gastric varices and compare the result to controls.