Abdominal aortic aneurysms: rupture signs on computed tomography

Transcription

1 Abdominal aortic aneurysms: rupture signs on computed tomography Poster No.: C-0798 Congress: ECR 2014 Type: Educational Exhibit Authors: K. N. Vu, Y. Kaitoukov, F. Morin-Roy, C. Kauffman, M.-F GIROUX, G. Soulez, A. Tang ; Montreal, Qc/CA, Mont-Royal, Qc/CA Keywords: Haemorrhage, Aneurysms, Education, Complications, CTAngiography, CT, Vascular, Emergency, Abdomen DOI: /ecr2014/C-0798 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 54

2 Learning objectives The purpose of this educational exhibit is: To categorize abdominal aortic aneurysm (AAA) rupture signs according to their location; To detect computed tomography (CT) signs of impending or contained AAA rupture before completed AAA rupture; To illustrate the pathogenesis of AAA rupture signs. Page 2 of 54

3 Background Definition Abdominal aortic aneurysms (AAA) are defined as a focal dilation of the aorta of more than 50% of its expected diameter [1]. Epidemiology AAA are: Found in 1% of the population over the age of 50 [2]; Responsible for 1% of all deaths amongst Caucasian adults [3]; The tenth leading cause of death in men over the age of 55 [4]. Risk factors include age, male gender, hypercholesterolemia, and hypertension [5]. tobacco usage, family history, Natural history Aneurysms may progress in size as a result of gradual wall weakening [6], with rupture occurring at the end of the growth spectrum. Rupture risk significantly increases when AAA diameters exceed 4.5 cm in women and 5.5 cm in men [7] (Table 1). Table 1: Annual rupture risk according to abdominal aortic aneurysm diameter. Page 3 of 54

4 References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA, adapted from Brewster DC et al. (2003) Guidelines for the treatment of abdominal aortic aneurysms. J Vasc Surg 37: A ruptured AAA has a 90% mortality rate [8]. However, hemodynamically stable patients with an impending AAA rupture can benefit from preoperative management that optimizes surgical conditions and reduces mortality rates to those comparable to elective procedures (less than 5%) [5, 9]. It is therefore crucial to identify impending AAA ruptures before rupture is completed. Imaging findings Imaging findings of AAA rupture can be categorized according to their location: (1) intramural, (2) luminal, and (3) extraluminal (Table 2). Intramural signs generally indicate impending AAA rupture, whereas luminal and extraluminal signs imply complete rupture. Table 2: Classification of signs of impending and complete aortic aneurysm rupture according to location: intramural, luminal, and extraluminal. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Page 4 of 54

5 Findings and procedure details Intramural signs Rapid enlargement rate AAA growth rate is correlated to its diameter and to the risk of rupture [4, 10]. When aneurysm growth rate exceeds 1 cm per year, the increased rupture risk justifies elective AAA repair [5, 10] (Fig. 1-4). Page 5 of 54

6 Fig. 1: Rapid enlargement rate - Axial enhanced CT of a 71-year-old man shows a 5.4 cm AAA. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Fig. 2: Rapid enlargement rate - 3D rendering image for the CT examination in Fig. 1 depicts the diameter with a color parametric map. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Page 6 of 54

7 Fig. 3: Rapid enlargement rate - Axial enhanced CT of the same patient performed a year later shows a 1 cm increase in diameter. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Page 7 of 54

8 Fig. 4: Rapid enlargement rate - 3D rendering image for the CT examination in Fig. 3 depicts the diameter with a color parametric map. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Focal wall discontinuity Many aneurysms are lined with circumferential wall calcifications. In impending or complete AAA rupture, a focal discontinuity within the intimal calcifications can be seen indicating the rupture site, which is most commonly observed on the posterolateral wall [11] (Fig. 5-7). Page 8 of 54

9 Fig. 5: Focal wall discontinuity - Illustration depicts a focal discontinuity (white arrow) within calcified intima walls (C), indicating AAA rupture site. References: Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 9 of 54

10 Fig. 6: Focal wall discontinuity - Axial unenhanced CT image of an asymptomatic 78year-old woman shows an 8 cm AAA with intact circumferential calcified walls. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Page 10 of 54

11 Fig. 7: Focal wall discontinuity - Axial unenhanced CT image of the same patient who presented with severe abdominal pain 5 days later. A new 1 cm focal gap (white arrow) of the circumferential calcifications can be seen with retroperitoneal hemorrhage (R). References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Hyperattenuating crescent sign Although intramural thrombus can be regarded as a protective factor against rupture, in fact, intrinsic metabolic activity within the thrombus weakens the underlying aortic wall [12]. When intraluminal blood dissects into the thrombus and comes into contact with the weakened aortic wall, rupture risk is increased [12-14]. The dissecting blood can be seen as a high-attenuating crescent underlying the intramural thrombus or lying within the aortic wall [6] (Fig. 8-9). Page 11 of 54

12 Fig. 8: Hyperattenuating crescent sign - Illustration demonstrates blood (black arrow) dissecting into a mural thrombus (T) from the aortic lumen (L). The resulting intramural hematoma (H) is crescent-shaped. References: Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 12 of 54

13 Fig. 9: Hyperattenuating crescent sign - Axial unenhanced CT of an 83-year-old man presenting with abdominal pain and pulsating mass. The crescent (H) of higher attenuation than the aortic lumen (L) is a sign of impending aneurysm rupture despite the absence of retroperitoneal hematoma. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Thrombus fissuration Following the same concept described for the hyperattenuating crescent sign, blood dissection into intramural thrombus can be seen as thrombus fissuration [6]. This sign is observed on enhanced CT as linear contrast infiltrations from the patent aortic lumen through the intramural thrombus (Fig ). Page 13 of 54

14 Fig. 10: Thrombus fissuration - Illustration demonstrates blood (black arrow) dissecting from the aortic lumen (L) into a mural thrombus (T). The infiltrating blood is seen as linear fissurations (white arrows). References: Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 14 of 54

15 Fig. 11: Thrombus fissuration - Axial enhanced CT of a 64-year-old man shows linear infiltrations of contrast material (white arrows) within the hypodense mural thrombus. The patient underwent successful emergent AAA repair before complete rupture occurred. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Draped aorta sign A draped aorta sign can be seen in contained AAA ruptures, when rupture site is posterior and sealed by the adjacent vertebral body [9]. The posterior wall of the aorta molds to the anterior surface of the vertebra. Normal fat planes between the aneurysm and vertebra are lost (Fig ). Page 15 of 54

16 Fig. 12: Draped aorta sign - Illustration depicts loss of normal aneurysm wall convexity. The posterior wall of the aorta molds to the anterior surface of the vertebral body. References: Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 16 of 54

17 Fig. 13: Draped aorta sign - Axial enhanced CT of an 85-year-old man with abdominal pain. The posterior aortic wall follows the contour of anterior portion of the vertebra, with loss of fat planes between the aneurysm and vertebra (white arrowheads). Thrombus fissuration (white arrow) is also seen. These are both signs of impending AAA rupture. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Luminal signs Aortoenteric fistula Aortoenteric fistulas are an abnormal communication between the aorta and a bowel loop. Imaging findings include intra- and extraluminal gas within the aneurismal sac and loss of fat planes between the aneurysm and involved bowel segment. Contrast extravasation into the bowel lumen can sometimes be seen on enhanced CT when the patient is actively bleeding. The third and fourth portions of the duodenum are involved in over 50% of aortoenteric fistulas [5] (Fig ). Page 17 of 54

18 Fig. 14: Aortoenteric fistula - Illustration depicts a fistulous tract connecting a bowel loop to an aortic aneurysm. The white double-headed arrow shows communication between the structures allowing bowel gas to infiltrate into the aortic wall and blood to leak into the bowel lumen. References: Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 18 of 54

19 Fig. 15: Aortoenteric fistula - Sagittal enhanced CT image of a 73-year-old man demonstrates an aortoenteric fistula. Intraluminal gas (white arrow) is observed within the AAA and normal fat planes between the aneurysm and the third portion of the duodenum are lost (white arrowhead). References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Page 19 of 54

20 Fig. 16: Aortoenteric fistula - Axial enhanced CT of an 82-year-old man who presented with massive lower gastrointestinal bleeding and a history of previously repaired AAA. Active contrast extravasation (white arrow) into the third portion of the duodenum (D) and the stomach (S) can be seen in this patient with aortoenteric fistula. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Aortocaval fistula An aortocaval fistula is a rare entity that affects less than 1% of AAA and 2-4% of ruptured aneurysms [15, 16]. On unenhanced CT, normal fat planes between AAA and inferior vena cava (IVC) is obliterated and IVC may appear dilated. On arterial phase CT angiography, contrast enhances AAA and IVC simultaneously, whereas renal cortex and femoral arteries show later enhancement [16] (Fig ). Page 20 of 54

21 Fig. 17: Aortocaval fistula - Axial arterial phase enhanced CT shows simultaneous enhancement of AAA and IVC in an 83-year-old man with AAA rupture and retroperitoneal hematoma (R). References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Page 21 of 54

22 Fig. 18: Aortocaval fistula - Axial enhanced CT of the same patient at a lower level demonstrates active contrast extravasation (white arrows) from the aortic aneurysm to the IVC with loss of normal fat planes between the structures. Retroperitoneal hematoma (R) can also be seen. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Extraluminal signs Periaortic stranding Page 22 of 54

23 Periaortic fat stranding is frequently observed in impending rupture and may be the earliest sign before complete AAA rupture [4]. It represents edema of the periaortic fat [17] and can be seen before visualization of retroperitoneal hematoma (Fig. 19). Fig. 19: Periaortic stranding - Coronal enhanced CT of a 59-year-old man with abdominal pain shows stranding of periaortic fat (white arrows) before any retroperitoneal hematoma can be seen. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Contrast extravasation Page 23 of 54

24 Contrast extravasation is the most specific sign for a complete AAA rupture. On arterial phase enhanced CT, contrast material from the AAA lumen is seen escaping through the boundaries of the aneurysm wall into the retroperitoneal space (Fig. 20). Fig. 20: Contrast extravasation - Axial enhanced CT of a 75-year-old woman demonstrates active contrast extravasation (white arrows) from the aneurysm lumen (L) into the retroperitoneal space with massive retroperitoneal hematoma (R). References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc Montreal/CA Retroperitoneal hematoma The most common sign of a ruptured AAA is the concomitant presence of an AAA and an adjacent hematoma in the retroperitoneal space [1, 14]. Acute hemorrhage can be seen as a high-attenuating fluid collection of 30 HU or more [4], although lower attenuation values do not exclude hematoma. Bleeding may extend into multiple retroperitoneal Page 24 of 54

25 compartments, such as the perirenal, anterior and posterior pararenal spaces, and along the psoas muscle [18] (Fig. 21). Fig. 21: Retroperitoneal hematoma - Axial unenhanced CT image of a 72-year-old man demonstrates hemorrhage involving left anterior (AP) and posterior (PP) pararenal spaces and along the left psoas muscle (P). The left kidney is displaced laterally. Attenuation of 45 HU (more than 30 HU) indicates acute hematoma. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Intraperitoneal hematoma Bleeding from a ruptured AAA may extend into the intraperitoneal compartment. Hemoperitoneum can be seen in the perihepatic space, within mesenteric folds, along Page 25 of 54

26 paracolic gutters, or within the pouch of Douglas. Such intraperitoneal hematomas are more commonly associated with rupture of the anterior or anterolateral aortic aneurysm wall [19] (Fig ). Fig. 22: Intraperitoneal hematoma - Illustration depicts AAA rupture of the left anterolateral wall (white arrow). Massive hemorrhage extends into both retroperitoneal (R, shown as translucent red blood) and intraperitoneal (I, shown as more opaque blood) spaces. References: Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 26 of 54

27 Fig. 23: Intraperitoneal hematoma - Coronal unenhanced CT of a 51-year-old man demonstrates intraperitoneal hematoma involving perihepatic space (PH), right (RG), and left (LG) paracolic gutters. Retroperitoneal hematoma (white arrows) is also seen. Attenuation of 60 HU indicates acute hemorrhage. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA Differential diagnosis Some of the signs previously mentioned are not entirely specific to impending or complete AAA rupture and can be seen in other pathologies [4, 20] (Table 3). Page 27 of 54

28 Table 3: Differential diagnosis of various impending and complete AAA rupture imaging findings. References: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/ CA, adapted from Bhalla S et al. (2003) CT of acute abdominal aortic disorders. Radiol Clin North Am 41: and Federle MP et al. (2007) CT criteria for differentiating abdominal hemorrhage: anticoagulation or aortic aneurysm rupture? AJR Am J Roentgenol 188: Page 28 of 54

29 Images for this section: Fig. 1: Rapid enlargement rate - Axial enhanced CT of a 71-year-old man shows a 5.4 cm AAA. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 29 of 54

30 Fig. 2: Rapid enlargement rate - 3D rendering image for the CT examination in Fig. 1 depicts the diameter with a color parametric map. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 30 of 54

31 Fig. 3: Rapid enlargement rate - Axial enhanced CT of the same patient performed a year later shows a 1 cm increase in diameter. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 31 of 54

32 Fig. 4: Rapid enlargement rate - 3D rendering image for the CT examination in Fig. 3 depicts the diameter with a color parametric map. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 32 of 54

33 Fig. 5: Focal wall discontinuity - Illustration depicts a focal discontinuity (white arrow) within calcified intima walls (C), indicating AAA rupture site. Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 33 of 54

34 Fig. 6: Focal wall discontinuity - Axial unenhanced CT image of an asymptomatic 78year-old woman shows an 8 cm AAA with intact circumferential calcified walls. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 34 of 54

35 Fig. 7: Focal wall discontinuity - Axial unenhanced CT image of the same patient who presented with severe abdominal pain 5 days later. A new 1 cm focal gap (white arrow) of the circumferential calcifications can be seen with retroperitoneal hemorrhage (R). Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 35 of 54

36 Fig. 8: Hyperattenuating crescent sign - Illustration demonstrates blood (black arrow) dissecting into a mural thrombus (T) from the aortic lumen (L). The resulting intramural hematoma (H) is crescent-shaped. Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 36 of 54

37 Fig. 9: Hyperattenuating crescent sign - Axial unenhanced CT of an 83-year-old man presenting with abdominal pain and pulsating mass. The crescent (H) of higher attenuation than the aortic lumen (L) is a sign of impending aneurysm rupture despite the absence of retroperitoneal hematoma. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 37 of 54

38 Fig. 10: Thrombus fissuration - Illustration demonstrates blood (black arrow) dissecting from the aortic lumen (L) into a mural thrombus (T). The infiltrating blood is seen as linear fissurations (white arrows). Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 38 of 54

39 Fig. 11: Thrombus fissuration - Axial enhanced CT of a 64-year-old man shows linear infiltrations of contrast material (white arrows) within the hypodense mural thrombus. The patient underwent successful emergent AAA repair before complete rupture occurred. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 39 of 54

40 Fig. 12: Draped aorta sign - Illustration depicts loss of normal aneurysm wall convexity. The posterior wall of the aorta molds to the anterior surface of the vertebral body. Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 40 of 54

41 Fig. 13: Draped aorta sign - Axial enhanced CT of an 85-year-old man with abdominal pain. The posterior aortic wall follows the contour of anterior portion of the vertebra, with loss of fat planes between the aneurysm and vertebra (white arrowheads). Thrombus fissuration (white arrow) is also seen. These are both signs of impending AAA rupture. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 41 of 54

42 Fig. 14: Aortoenteric fistula - Illustration depicts a fistulous tract connecting a bowel loop to an aortic aneurysm. The white double-headed arrow shows communication between the structures allowing bowel gas to infiltrate into the aortic wall and blood to leak into the bowel lumen. Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 42 of 54

43 Fig. 15: Aortoenteric fistula - Sagittal enhanced CT image of a 73-year-old man demonstrates an aortoenteric fistula. Intraluminal gas (white arrow) is observed within the AAA and normal fat planes between the aneurysm and the third portion of the duodenum are lost (white arrowhead). Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 43 of 54

44 Fig. 16: Aortoenteric fistula - Axial enhanced CT of an 82-year-old man who presented with massive lower gastrointestinal bleeding and a history of previously repaired AAA. Active contrast extravasation (white arrow) into the third portion of the duodenum (D) and the stomach (S) can be seen in this patient with aortoenteric fistula. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 44 of 54

45 Fig. 17: Aortocaval fistula - Axial arterial phase enhanced CT shows simultaneous enhancement of AAA and IVC in an 83-year-old man with AAA rupture and retroperitoneal hematoma (R). Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 45 of 54

46 Fig. 18: Aortocaval fistula - Axial enhanced CT of the same patient at a lower level demonstrates active contrast extravasation (white arrows) from the aortic aneurysm to the IVC with loss of normal fat planes between the structures. Retroperitoneal hematoma (R) can also be seen. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 46 of 54

47 Fig. 19: Periaortic stranding - Coronal enhanced CT of a 59-year-old man with abdominal pain shows stranding of periaortic fat (white arrows) before any retroperitoneal hematoma can be seen. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 47 of 54

48 Fig. 20: Contrast extravasation - Axial enhanced CT of a 75-year-old woman demonstrates active contrast extravasation (white arrows) from the aneurysm lumen (L) into the retroperitoneal space with massive retroperitoneal hematoma (R). Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 48 of 54

49 Fig. 21: Retroperitoneal hematoma - Axial unenhanced CT image of a 72-year-old man demonstrates hemorrhage involving left anterior (AP) and posterior (PP) pararenal spaces and along the left psoas muscle (P). The left kidney is displaced laterally. Attenuation of 45 HU (more than 30 HU) indicates acute hematoma. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 49 of 54

50 Fig. 22: Intraperitoneal hematoma - Illustration depicts AAA rupture of the left anterolateral wall (white arrow). Massive hemorrhage extends into both retroperitoneal (R, shown as translucent red blood) and intraperitoneal (I, shown as more opaque blood) spaces. Medical illustration copyright ownership: Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 50 of 54

51 Fig. 23: Intraperitoneal hematoma - Coronal unenhanced CT of a 51-year-old man demonstrates intraperitoneal hematoma involving perihepatic space (PH), right (RG), and left (LG) paracolic gutters. Retroperitoneal hematoma (white arrows) is also seen. Attenuation of 60 HU indicates acute hemorrhage. Radiology, Université de Montréal, CHUM Hôpital Saint-Luc - Montreal/CA Page 51 of 54

52 Conclusion AAA rupture occurs at the end of a continuum of growth and wall weakening. Although ruptured AAA are easily diagnosed, identifying impending rupture signs can be more challenging. This educational exhibit describes the CT imaging findings that may help identify impending rupture prior to complete rupture, which has important consequences on treatment and prognosis. Familiarity with alternative causes of retroperitoneal stranding and hemorrhage may also facilitate diagnosis. Page 52 of 54

53 References Johnston KW, Rutherford RB, Tilson MD, Shah DM, Hollier L, Stanley JC (1991) Suggested standards for reporting on arterial aneurysms. Subcommittee on Reporting Standards for Arterial Aneurysms, Ad Hoc Committee on Reporting Standards, Society for Vascular Surgery and North American Chapter, International Society for Cardiovascular Surgery. J Vasc Surg 13: Bengtsson H, Sonesson B, Bergqvist D (1996) Incidence and prevalence of abdominal aortic aneurysms, estimated by necropsy studies and population screening by ultrasound. Ann N Y Acad Sci 800:1-24 Singh K, Bonaa KH, Jacobsen BK, Bjork L, Solberg S (2001) Prevalence of and risk factors for abdominal aortic aneurysms in a population-based study : The Tromso Study. Am J Epidemiol 154: Bhalla S, Menias CO, Heiken JP (2003) CT of acute abdominal aortic disorders. Radiol Clin North Am 41: Chaikof EL, Brewster DC, Dalman RL et al (2009) The care of patients with an abdominal aortic aneurysm: the Society for Vascular Surgery practice guidelines. J Vasc Surg 50:S2-49 Arita T, Matsunaga N, Takano K et al (1997) Abdominal aortic aneurysm: rupture associated with the high-attenuating crescent sign. Radiology 204: Brewster DC, Cronenwett JL, Hallett JW, Jr., Johnston KW, Krupski WC, Matsumura JS (2003) Guidelines for the treatment of abdominal aortic aneurysms. Report of a subcommittee of the Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. J Vasc Surg 37: Powell JT, Greenhalgh RM (2003) Clinical practice. Small abdominal aortic aneurysms. N Engl J Med 348: Apter S, Rimon U, Konen E et al (2008) Sealed rupture of abdominal aortic aneurysms: CT features in 6 patients and a review of the literature. Abdom Imaging 35: Limet R, Sakalihassan N, Albert A (1991) Determination of the expansion rate and incidence of rupture of abdominal aortic aneurysms. J Vasc Surg 14: Fillinger MF, Racusin J, Baker RK et al (2004) Anatomic characteristics of ruptured abdominal aortic aneurysm on conventional CT scans: Implications for rupture risk. J Vasc Surg 39: Roy J, Labruto F, Beckman MO, Danielson J, Johansson G, Swedenborg J (2008) Bleeding into the intraluminal thrombus in abdominal aortic aneurysms is associated with rupture. J Vasc Surg 48: Pillari G, Chang JB, Zito J et al (1988) Computed tomography of abdominal aortic aneurysm. An in vivo pathological report with a note on dynamic predictors. Arch Surg 123: Page 53 of 54

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