Contribution of PET scanning to the evaluation of abdominal aortic aneurysm.

The size of abdominal aortic aneurysms (AAA) is the most usual predictor of the risk for rupture. Because chronic metalloproteinases production and activation by inflammatory cells causes degradation of elastin and collagen in the aneurysmal wall, the detection of an increased metabolic process preceding fissuration and rupture could be a more sensitive predictor of rupture risk. We investigated the metabolic activity of the aneurysmal wall by whole-body positron emission tomography (PET) in 26 patients with a documented AAA (mean diameter 63 mm, extremes 45 mm and 78 mm). A positive (18)F-fluorodeoxyglucose ((18)F-FDG) uptake at the level of the AAA was observed in 38% of the cases (10 of 26 patients). Nine of these 10 patients required emergent or urgent aneurysmectomy for ruptured (n = 1), leaking (n = 1), rapidly expanding (n = 2), or painful (n = 5) aneurysms; the negative (18)F-FDG uptake patients had a more benign course. This preliminary study suggests a possible correlation between (18)F-FDG uptake by the aneurysm wall and the triggering of processes leading to rupture. The (18)F-FDG uptake in the aneurysm wall may correspond to the accumulation of inflammatory cells responsible for the production and activation of degrading enzymes. PET scan seems useful in high-risk patients. Positive PET imaging in these cases would help us to decide to proceed with surgery, despite factors favoring a surveillance strategy.