Renal Artery Aneurysms Rarely Rupture, Have a Slow Growth Rate, and Small Aneurysms are Stabilised by Extensive Calcification of the Aneurysm Wall.

Abstract

This retrospective observational study aimed to analyse renal artery aneurysm (RAA) imaging and patient related parameters and their impact on RAA growth and rupture. The term "aneurysm" was searched for in radiology reports of abdominal imaging studies from a university hospital district area from 2006 to 2020. Medical records, computed tomography scans, and magnetic resonance imaging scans of patients with RAA were reviewed to obtain demographic and clinical data as well as information on the size, morphology, laterality, location, calcification, thrombus, and growth of the aneurysm during follow up. Multivariable tests were used to analyse factors affecting RAA growth. Four hundred and thirty-eight RAAs in 380 patients were identified from 35 378 radiology reports. The mean RAA diameter ± standard deviation at presentation was 15.3 ± 6.1 mm, and 402 (91.8%) were saccular. Calcification was detected in 322 (73.5%), with 273 aneurysms (62.3%) showing extensive (over one third circumferential) calcification. Seventeen growing or large aneurysms were treated invasively at a median size of 27 mm (interquartile range 24, 33), leaving no ruptures during follow up. Follow up imaging for more than six months was available for 324 RAAs (74.0%), with a mean follow up of 75.8 ± 48.7 months. Eighteen aneurysms (5.6% of the 324 RAAs with six month imaging follow up) grew, with a mean growth rate of 0.70 ± 0.8 mm/year. On multivariable analysis, aneurysm size ≤ 15 mm (odds ratio [OR] 0.28, 95% confidence interval [CI] 0.074 - 0.70; p = .010) and extensive wall calcification (OR 0.18, 95% CI 0.043 - 0.73; p = .016) were protective for aneurysm growth and rupture. Rupture of RAAs is rare, and growth is slow. Small aneurysm size (≤ 15 mm) and extensive wall calcification were found to be independent protective factors, suggesting that aneurysms with both these features may require less frequent follow up. The data support adherence to intervention thresholds in current practice guidelines.