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.