Short segment linear "flaps" of the abdominal aorta: proposed mechanism of origin and evaluation of natural history via retrospective imaging review.

purposeLuminal linear findings (LLF) of the abdominal aorta are often called aortic "flaps," triggering concern for acute aortic syndrome. However, these "flaps" are unlikely to represent intimomedial dissection given isolation to the abdominal aorta, short length, and incidental discovery. We aim to characterize the etiology and stability of LLF.

methodsCT reports finalized January 2021-December 2022 were queried for terms "focal dissection," "dissection flap," "linear filling defect," and "linear flap." Patients were excluded for thoracoabdominal dissection, LLF in non-aortic vessel, no prior contrast-enhanced imaging, and less than 6 months between exams. Index exam reviewed for presence of LLF, atherosclerosis, and aortic caliber at LLF site. Prior exam assessed for aortic caliber and aortic findings at subsequent LLF site. Patients with unchanged LLF between exams were categorized "Stable" and patients with interval change "Dynamic."

resultsSeven hundred and two cases identified. After exclusions, imaging from 70 patients reviewed; 1 excluded for no LLF. Stable Cohort of 39 patients had median follow-up 31 months (range 6-284 months). 87% of aortas were moderately/severely atherosclerotic (n = 16 moderate, n = 18 severe), while 69% were ectatic/aneurysmal (n = 27). Dynamic Cohort of 20 patients had median follow-up of 70 months (range 14-244 months). All were atherosclerotic and 80% were ectatic/aneurysmal compared to 25% ectatic/aneurysmal at prior imaging. Mural thrombus was present at the site of the future LLF in 17 of 20, thrombosed PAU in 1, and no focal findings in 2.

conclusionShort-segment LLFs within the abdominal aorta arise from prior mural thrombus and demonstrate long term stability. Clinically and radiographically indolent, LLFs should not be called dissection flaps.