title: Bleeding into the intraluminal thrombus in abdominal aortic aneurysms is associated with rupture.
abstract: OBJECTIVE
  The aim of this study was to determine signs of bleeding in the intraluminal thrombus and the site of rupture using multislice computed tomography (CT) imaging in patients with abdominal aortic aneurysms (AAA).
  
  
  METHODS
  We analyzed CT images of 42 patients with ruptured infrarenal AAA in two hospitals in Stockholm, Sweden during a 3-year period. A "crescent sign" or localized areas with higher attenuation in the thrombus were interpreted as signs of bleeding in the thrombus. A localized area of hyperattenuation did not have the typical crescent shape and was distinguished from calcifications in the thrombus. We measured the attenuation in Hounsfield units in the intraluminal thrombus using CT software to quantify the presence of blood in the thrombus. As controls, we analyzed 36 patients with intact AAA and a comparable aneurysm diameter and age.
  
  
  RESULTS
  The crescent sign was more frequent in the ruptured group (38% vs 14%, P = .02), but there was no significant difference in the presence of localized areas of hyperattenuation in the two groups. The attenuation in the thrombus was significantly higher in patients with rupture than in those with intact aneurysms (P = .02). The site of rupture could be localized in 29/42 patients. Ruptures occurred both through the thrombus-covered and the thrombus free wall. In 45% of the patients, the rupture site was localized in the left lateral wall, in 24% in the anterior wall, in 24% in the right lateral wall, but only in 7% in the posterior wall.
  
  
  CONCLUSIONS
  The site of rupture could be identified in a majority of cases of AAA with routine multislice CT. This study demonstrates an association between the presence of blood in the thrombus as suggested by higher attenuation levels and a crescent sign and AAA rupture. If these findings also predict AAA rupture, remains to be established.
authors.affiliation: Department of Surgery, Capio St. Görans Hospital, Stockholm, Sweden. joy.roy@ki.se
authors.forename: Joy
authors.initials: J
authors.lastname: Roy
authors.forename: Fausto
authors.initials: F
authors.lastname: Labruto
authors.forename: Mats O
authors.initials: MO
authors.lastname: Beckman
authors.forename: Jesper
authors.initials: J
authors.lastname: Danielson
authors.forename: Gunnar
authors.initials: G
authors.lastname: Johansson
authors.forename: Jesper
authors.initials: J
authors.lastname: Swedenborg
mesh_terms: D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000150:complications / Q000000981:diagnostic imaging*; D001019:Aortic Rupture / Q000000981:diagnostic imaging / Q000209:etiology*; D001027:Aortography / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D006470:Hemorrhage / Q000150:complications / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D016347:Medical Records Systems, Computerized; D011237:Predictive Value of Tests; D012307:Risk Factors; D013548:Sweden; D013927:Thrombosis / Q000150:complications / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed