To prospectively investigate the natural history of asymptomatic pseudoaneurysm after robotic-assisted partial nephrectomy.
Robotic-assisted partial nephrectomy was undertaken for 67 patients between July 2014 and July 2018. Patients who could not undergo enhanced CT were excluded, so 60 patients were finally included in the present study. We prospectively investigated the presence of pseudoaneurysm based on early enhanced CT scan on postoperative day 7. According to our treatment policy, patients with symptomatic pseudoaneurysm underwent selective transarterial embolization. Meanwhile, patients with asymptomatic pseudoaneurysm were observed with follow-up CT imaging, regardless of the size of the aneurysm.
Overall incidence of pseudoaneurysm on postoperative day 7 was 18% (11/60 cases). The median size of the pseudoaneurysm was 9 mm (quartile: 6-12 mm). Two patients with symptomatic pseudoaneurysm underwent selective transarterial embolization. Nine patients had asymptomatic pseudoaneurysm; in eight of these it disappeared without therapeutic intervention. The median period from surgery to confirmed disappearance of the aneurysm was 19 days (quartile 14-32 days). In the remaining one patient, small asymptomatic pseudoaneurysm (2 mm) could still be observed even one year after surgery.
Our study showed high incidence of pseudoaneurysm one week after robotic-assisted partial nephrectomy that mostly disappeared without therapeutic intervention. Routine enhanced CT screening and pre-emptive embolization may not be necessary for asymptomatic renal artery pseudoaneurysm.

Copyright © 2020. Published by Elsevier Inc.