title: Asymmetric expansion of aortic aneurysms on computed tomography imaging.
abstract: OBJECTIVE
  To investigate whether wall growth during aneurysm development spares the aortic wall between the intercostal or lumbar arteries or, alternatively, is uniform around the circumference.
  
  
  METHODS
  Computed tomography scans of 155 patients with aortic aneurysms (40 thoracic, 50 thoracoabdominal, and 65 abdominal) in a single hospital of a large academic institution were retrospectively inspected. Computed tomography studies of 100 control subjects (40 thoracic and 60 abdominal) were also reviewed. In all 255 patients, the ratio of the arc length between the origins of the intercostal or lumbar arteries (interbranch arc length) to the remainder of the aortic residual circumference was calculated. These ratios were compared between all subjects with aneurysms and the controls at each vertebral body level and between those with thoracic or thoracoabdominal or abdominal aneurysms and controls at each vertebral body level.
  
  
  RESULTS
  Interbranch arc lengths and residual aortic circumferences were larger in aneurysm patients than in control subjects, but the differences were statistically significant only at T4 and from T8 to L4 (P = .009 to P < .001) and from T4 to L4 (P < .001), respectively. The ratio of interbranch arc length to residual circumference in aneurysmal aortas was significantly smaller than that in controls at 12 out of 13 levels from T4 to L4 (P = .004 to P < .001). There was a statistically significant smaller ratio at 8 out of 9 levels for thoracic aneurysms (P = .006 to P < .001), 12 out of 13 levels for thoracoabdominal aneurysms (P = .008 to P < .001), and 3 out of 4 levels for abdominal aneurysms compared with controls (P = .006 to P < .001).
  
  
  CONCLUSIONS
  Wall growth in aortic aneurysms is asymmetric, with greater aneurysmal growth in the anterior aorta wall and relative sparing of the portion of aortic wall between the intercostal or lumbar arteries. The mechanisms effecting this asymmetric growth have not been fully characterized.
authors.affiliation: Department of Radiology, Division of Cardiothoracic Radiology, University of Michigan Medical Center, Ann Arbor, MI 48109-5302, USA. pcronin@med.umich.edu
authors.forename: Paul
authors.initials: P
authors.lastname: Cronin
authors.forename: Gilbert R
authors.initials: GR
authors.lastname: Upchurch
authors.forename: Himanshu J
authors.initials: HJ
authors.lastname: Patel
authors.forename: G Michael
authors.initials: GM
authors.lastname: Deeb
authors.forename: Aine Marie
authors.initials: AM
authors.lastname: Kelly
authors.forename: David M
authors.initials: DM
authors.lastname: Williams
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging*; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging*; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging*; D017545:Aortic Aneurysm, Thoracic / Q000000981:diagnostic imaging*; D001027:Aortography / Q000379:methods*; D018450:Disease Progression; D005260:Female; D006801:Humans; D016014:Linear Models; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D013904:Thoracic Vertebrae; D013997:Time Factors