Retrospective Review of Billowing Phenomenon-A Mimic of Endoleak Following Placement of Endologix Covered Stent for the Treatment of Abdominal Aortic Aneurysm.

BACKGROUND

Billowing is a unique computed tomography (CT) finding of the Endologix stent graft where a rim of contrast is observed outside the stent's endoskeleton but still contained within the graft cover. The purpose of this study is to evaluate the incidence and clinical outcome of billowing following an Endologix stent-graft placement.

METHODS

All patients who underwent abdominal aortic aneurysm (AAA) repair with endovascular placement of an Endologix stent graft from January 2002 to September 2013 and who were followed with imaging were included in the study. The images were evaluated for the incidence of billowing. Demographics and clinical outcomes were also analyzed.

RESULTS

One hundred twenty-two patients received an Endologix stent graft for AAA repair at our institution. One hundred patients qualified for this study. Eighty-four patients had billowing with the majority (70 patients) having crescentic billowing, and the remaining 14 patients having focal outpouching. Average billowing thickness measured 4.2 mm (range 1-13). Sixty-three patients with billowing had multiple follow-up CT angiograms to allow serial monitoring. Twelve patients had resolution of billowing, 11 patients had reduction in billowing size, 14 patients had no change in billowing size, and 26 patients had increase in billowing size. Patients with billowing had a statistically significant reduction in aneurysm sac size in anteroposterior and transverse dimensions (P = 0.014 and 0.009, respectively). Five cases of billowing were misdiagnosed as endoleak. Nineteen true endoleaks were identified, of which 13 cases were associated with billowing.

CONCLUSIONS

Billowing does not seem to be associated with increased morbidity, mortality, increase in aneurysm size, or presence of endoleak. Billowing should be recognized as a common and benign finding of the Endologix stent.