The Presence of Gas in Aneurysm Sac during Early Postoperative Period Is Associated to the Type of Endograft and Perfused Lumen's Size

BACKGROUND: The aim of the present study was to examine the frequency of gas within the aneurysm sac following endovascular aneurysm repair (EVAR) on early postoperative computed tomography (CT) scans, to measure its volume, record the location, and analyze anatomical and procedural risk factors of its presence.

METHODS: A retrospective analysis of prospectively collected data of patients undergoing standard, fenestrated, or branched EVAR between January 2013 and December 2015 was undertaken. The presence, position, and size of gas in the postoperative computed tomography angiography (CTA) (within 10 days) was examined, classified as (1) gas near aortic wall; (2) between aortic wall and endograft; and (3) near endograft and further analyzed in terms of anatomical and procedural risk factors associated with its presence.

RESULTS: From a total of 241 (85% males, 204/241 and 15% females, 37/241) patients who were treated with EVAR, CTA within 10 days was available in 211 patients with mean age of 73 ± 8.3 years. Gas was present on postoperative CT scan in 83 of 211 (39%) patients; 59/83 (71%) standard, 19/83 (23%) fenestrated, and 5/83 (6%) branched EVAR. The location of the gas was more frequently near the aortic wall (a) (46/83; 55.4%), with the mean gas volume to be 0.41 mL (range 0.01-2.74). Endoleak type II was diagnosed in 31.2% (66/211) of the cases and was not associated with the presence of gas (20/83; presence vs. 46/128; absence of gas; P = 0.069). The presence of gas was associated with larger preoperative diameter of the aortic perfused lumen (P = 0.013). The type of graft was correlated to the presence of gas on postoperative CTA (more frequent in standard EVAR [odds ratio 8; 95% confidence interval {CI} 2.01-31.25] and fenestrated [odds ratio 5.81; 95% CI 1.41-23.81]). In standard EVAR patients, the presence of gas was more frequently identified in early CTA (<5 days) than in later one (6-10 days) (P = 0.000). During the first month follow-up, no patient demonstrated any signs of infection in clinical and radiological assessment.

CONCLUSIONS: The presence of gas in the aneurysm sac after EVAR is a frequent finding on postoperative CTA and not related to infection or endoleak. Type of stent graft and size of the perfused lumen is associated with the presence of gas.