Thrombus distribution and changes in aneurysm size following endovascular aortic aneurysm repair

To determine (a) changes in aneurysm size following endovascular repair, (b) the significance of collateral lumbar artery blood flow and (c) the relationship between thrombus distribution within the aneurysm sac and the development of a "lumbar endoleak".

72 patients treated with endovascular stent-grafts were followed up with spiral computed tomography for a median of 11 (range 3-27) months. The cross-sectional area of the aneurysm was measured at the point of maximum diameter pre- and post-operatively. The distribution and quantity of thrombus was recorded pre-operatively and this was related to changes in aneurysm size and the development of lumbar endoleaks post-operatively.

An increase in aneurysm size occurred in 22 patients, of whom 10 had endoleaks. Fifteen aneurysms did not change in size, including four with endoleak, and 35 aneurysms decreased in size with no endoleaks. There was a significant difference between the endoleak and no endoleak groups (Chi-squared test = 17.1 with 2 degrees of freedom (d.f.), p < 0.001). Nine endoleaks were from patent lumbar arteries. No patients with thick circumferential or posteriorly placed thrombus developed an endoleak arising from lumbar vessels (0/23 cases) compared to those with minimal or anteriorly placed thrombus (9/49 cases) (Chi-squared test with Yate's correction = 3.17 with 1 d.f., p < 0.1).

Aneurysms do not decrease in size in the presence of a lumbar endoleak, and some expand significantly. A number of aneurysms increase in size despite no evidence of an endoleak on computed tomography (CT). Patterns of thrombus distribution may be able to predict patients at risk from persistent endoleak via lumbar vessels.