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

Objectives: to determine (a) changes in aneurysm size following endovascula r repair, (b) the significance of collateral lumbar artery blood flow and ( c) the relationship between thrombus distribution within the aneurysm sac a nd the development of a "lumbar endoleak". Materials and Methods: 72 patients treated with endovascular stent-grafts w ere 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 p oint of maximum diameter pre- and post-operatively. The distribution and qu antity of thrombus was recorded pre-operatively and this was related to cha nges in aneurysm size and the development of lumbar endoleaks post-operativ ely. Results: an increase in aneurysm size occurred in 22 patients, of whom 10 h ad endoleaks. Fifteen aneurysms did not change in size, including four with endoleak, and 35 aneurysms decreased in size with no endoleaks. There tons 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 endole aks were from patent lumbar arteries. No patients with thick circumferentia l or posteriorly placed thrombus developed an endoleak arising from lumbar vessels (0/23 cases) compared to those with minimal or anteriorly placed th rombus (9/49 cases) (Chi-squared test with Yate's correction = 3.17 with 1 d.f., p<0.1). Conclusions: 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). Patter ns of thrombus distribution may be able to predict patients at risk from pe rsistent endoleak via lumbar vessels.