Natural history of asymptomatic renal artery pseudoaneurysm after robot-assisted partial nephrectomy

Background: We assessed the natural history of renal artery pseudoaneurysm (RAP) after robot-assisted partial nephrectomy (RAPN). Methods: From May 2016 to September 2020, 106 patients underwent RAPN for renal tumors at our institution. Among 100 patients, excluding 6 who were ineligible for contrast-enhanced computed tomography (CE-CT), 4 underwent renal artery selective embolization (RAE), of which 2 cases were emergency RAE within 7 days after RAPN and the other 2 were prophylactic RAE 8 or more days after RAPN. In 98 patients examined for the clinical course of asymptomatic RAP managed by surveillance, excluding the 2 who underwent emergency RAE, routine CE-CT was performed at 7 days, 1 month and 3 months after RAPN. Factors influencing the occurrence of RAP among these 98 patients, including the 2 who underwent emergency RAE and excluding the 2 who underwent prophylactic RAE, were analyzed by logistic regression analysis. Results: Median [interquartile range (IOR), range] observation period, age, radiographic tumor size, and maximum diameter of RAP were 20.8 (23.9, 3.0-57.6) months, 63 (18, 22-84) years, 23 (11, 9-48) mm, and 6.6 (5.2, 3.0-16.0) mm, respectively. CE-CT detected 28 RAPs in 23 (23.0%) of 100 patients by 7 days after RAPN and routine CE-CT detected 25 RAPs in 21 (21.4%) of 98 patients excluding 2 who underwent emergency RAE at 7 days after RAPN. RAP was diagnosed by routine CE-CT in 21 (21.4%), 1 (1.0%), and 0 (0%) patients at 7 days, 1 month, and 3 months after RAPN, respectively. In univariate analysis, age [odds ratio (OR) 0.144: 69-84 vs. 22-56 years old, P=0.0179], R.E.N.A.L [radius (tumor size as maximal diameter), exophytic/endophytic properties of tumor, nearness of tumor deepest portion to collecting system or sinus, anterior/posterior descriptor and location relative to polar line] nephrometry score (OR 1.374, P=0.0382), warm ischemic time (OR 1.085, P=0.0393), and renorrhaphy time (OR 1.055, P=0.0408) were significantly associated with the occurrence of RAP. In multivariate analysis, only age (OR 0.124, P=0.0148) was a significant factor. Conclusions: Asymptomatic RAP up to 15 mm in diameter resolved spontaneously 3 months after RAPN. Young age (under 56 years) may be a factor in the development of RAP.