ABSTRACTTo facilitate nerve preservation during robot-assisted radical prostatectomy (RP), hydrodissection (HD) using an injection catheter was performed. HD during RP is a nerve-sparing technique in which an epinephrine solution is injected into the lateral prostatic fascia to separate it from the prostatic capsule. Although the beneficial effects of HD on postoperative sexual function have been reported, HD has rarely been used in robot-assisted RP. The primary reason may be the potential benefits of robotic surgery, such as less bleeding, magnified surgical view, and fine movement of instruments; another possible reason is the difficulty of handling sharp needles in a narrow intra-abdominal surgical space of robot-assisted RP. For safe fluid injection, we performed HD using an injection catheter – commonly used for endoscopic upper gastrointestinal hemostasis – during robot-assisted RP. The required time to accomplish HD and the safety of the procedure were examined in 15 HD of 11 patients. Approximately 2 minutes (median, 118 seconds; interquartile range, 106–174 seconds) were needed for HD using the injection catheter. All patients had no complications, such as injuries to the intestine, vessels, or other organs. Postoperative bleeding did not occur in any patients. HD with an injection catheter enables surgeons to perform simple and safe nerve preservation during robot-assisted RP.