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Everything you need to know about Computed Tomography (CT) & CT Scanning

Vascular: Abdominal Aorta Imaging Pearls - Learning Modules | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
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  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up (2017)

  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up

  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up

  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up

    Computed tomography (CT) is a cross-sectional imaging modality that offers excellent spatial resolution, fast image acquisition times, and widespread availability. However, without contrast material administration, its ability to assess vascular structures is limited. Evaluation of the vessel lumen is accomplished through CT angiography (CTA), a technique that utilizes the administration of iodinated contrast material. The addition of 3- D volumetric postprocessing techniques allow the abdominal aorta and associated vasculature to be viewed in any obliquity and affords quantification of luminal diameter, cross-sectional area, and sac volume. A disadvantage of CTA includes potential nephrotoxicity from administered contrast material.

  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up

    Due to its superior spatial resolution and rapid image acquisition, CTA with 3-D volumetric reconstruction and vessel analysis has gained wide acceptance as the gold standard for pre-EVAR evaluation. The utilization of 3-D reconstruction software has become paramount in EVAR planning, as it diminishes the impact of vessel tortuosity on diameter and length measurements, in addition to reducing intraobserver variability. One author found that routine 3-D analysis of pre-EVAR images led to a significant reduction in Type I endoleaks. Reformatted CTA images in the coronal and sagittal planes should be utilized for increased diagnostic accuracy. In most cases, a CTA of the abdomen and pelvis is appropriate to ensure coverage of the entire aneurysm and vascular access.

  • Abdominal Aortic Aneuurysm: Facts
    Every year, 200,000 people in the U.S. are diagnosed with an abdominal aortic aneurysm (AAA).
    A ruptured AAA is the 15th leading cause of death in the country, and the 10th leading cause of death in men older than 55.
    Aneurysms run in families. If a first-degree relative has had an AAA, you are 12 times more likely to develop an abdominal aortic aneurysm. Of patients in treatment to repair an AAA, 15–25% have a first-degree relative with the same type of aneurysm.

  • Abdominal Aortic Aneurysm: Risk Factors Include;
    Smoking (strongest risk factor)
    Hypertension
    Older age (peak incidence at age 70 to 80)
    Family history (in 15 to 25%)
    Race (more common in whites than in blacks)
    Male sex

  • Abdominal Aortic Aneurysm: Facts
    Defined as aorta larger than 3 cm
    4 - 5.4 cm can be monitored
    Fusiform > 5.4 cm warrants repair

  • AAA: Rupture Risk
    Aortic aneurysm rupture 77-94% mortality rate
       - Risk factors for AAA rupture
       - female gender
       - larger baseline AAA diameter
       - hypertension
       - continued tobacco use
       - cardiac or renal transplant

  • AAA Size and Risk


  • Impending AAA Rupture
    Clinical diagnosis difficult
    CT indicators of aneurysm instability
       - Rapid increase in size
       - Lumen: plaque ulceration
       - Wall: Intramural hematoma
       - Periaortic: retroperitoneal or intraperitoneal hemorrhage
    Guide emergent surgical management

  • What should repair be done?
    Elective surgical repair is recommended for
       - Aneurysms > 5 to 5.5 cm (when risk of rupture increases to > 5 to 10%/yr), unless coexisting medical conditions contraindicate surgery
       - Additional indications for elective surgery include
       - Increase in aneurysm size by > 0.5 cm within 6 mo regardless of size
       - Chronic abdominal pain
       - Thromboembolic complications
       - Iliac or femoral artery aneurysm that causes lower-limb ischemia 

  • What if an AAA ruptures?
    Ruptured abdominal aortic aneurysms require immediate open surgery or endovascular stent grafting. Without treatment, mortality rate approaches 100%. With open surgical treatment, mortality rate is about 50%. Mortality with endovascular stent grafting is generally lower (20 to 30%).
    Merck Manual

  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up
    Computed tomography (CT) is a cross-sectional imaging modality that offers excellent spatial resolution, fast image acquisition times, and widespread availability. However, without contrast material administration, its ability to assess vascular structures is limited. Evaluation of the vessel lumen is accomplished through CT angiography (CTA), a technique that utilizes the administration of iodinated contrast material. The addition of 3- D volumetric postprocessing techniques allow the abdominal aorta and associated vasculature to be viewed in any obliquity and affords quantification of luminal diameter, cross-sectional area, and sac volume. A disadvantage of CTA includes potential nephrotoxicity from administered contrast material.

  • ACR Appropriateness Criteria® 
Abdominal Aortic Aneurysm: Interventional Planning and Follow-up
    Due to its superior spatial resolution and rapid image acquisition, CTA with 3-D volumetric reconstruction and vessel analysis has gained wide acceptance as the gold standard for pre-EVAR evaluation. The utilization of 3-D reconstruction software has become paramount in EVAR planning, as it diminishes the impact of vessel tortuosity on diameter and length measurements, in addition to reducing intraobserver variability. One author found that routine 3-D analysis of pre-EVAR images led to a significant reduction in Type I endoleaks. Reformatted CTA images in the coronal and sagittal planes should be utilized for increased diagnostic accuracy. In most cases, a CTA of the abdomen and pelvis is appropriate to ensure coverage of the entire aneurysm and vascular access.

  • BACKGROUND: Multidetector computed tomography angiography (MDCTA) and magnetic resonance angiography (MRA) are accurate techniques for selecting patients with peripheral arterial disease for surgical and endovascular treatment. No studies in the literature have directly compared MDCTA and MRA to establish which one should be employed, in patients suitable for both techniques, before endovascular treatment.


    CONCLUSION: Our results suggest that MDCTA can be considered as a first-line investigation in patients being candidates for endovascular procedures when clinical history or duplex sonographic evaluation are indicative of severe impairment of the infrapopliteal segment.

    
Comparison of CT and MR angiography in evaluation of peripheral arterial disease before endovascular intervention.
Cina A et al.
Acta Radiol. 2016 May;57(5):547-56.
  • RESULTS: MDCTA and MRA accurately classify disease in the aorto-iliac (accuracy 0.92 for MDCTA and MRA) and femoro-popliteal (MDCTA 0.94, MRA 0.90) segments. MDCTA was more accurate in stratifying disease in the infrapopliteal segments (0.96 vs. 0.9) and in assessing the impairment of runoff arteries (0.92 vs. 0.85) at per-segment analysis. MDCTA showed a higher confidence and a shorter examination time.


    Comparison of CT and MR angiography in evaluation of peripheral arterial disease before endovascular intervention.
Cina A et al.
Acta Radiol. 2016 May;57(5):547-56.
  • “Some classic signs may help in this tough mission, including the Draped Aorta sign. It refers to posterior aortic bulging and consequent loss of the interface between the aortic posterior wall and/or when the aneurism wall closely follows the contour of the adjacent vertebral bodies and psoas muscle. This sign may also be associated with vertebral erosions and is indicative of impending AAA rupture.”


    The draped aorta sign of impending aortic aneurysm rupture
 Fonseca, E.K.U.N., e Castro, A..A., Tames, A..V.C. et al. Abdom Radiol (2017). doi:10.1007/s00261-017-1114-7
  • “Excellent interobserver agreement was noted for each calcification score category. The common iliac arteries showed significantly higher average calcification scores than the external iliac arteries for all categories. Advanced age and diabetes mellitus were independently predictive of higher scores in each category, whereas hypertension, cigarette smoking, hyperlipidemia, and sex were not. Based on multivariate analysis, only the calcification morphology score of the arterial segment used for anastomosis was independently predictive of a higher rate of surgical complexity and of DGF. None of the scores was predictive of graft or patient survival. However, patients with CT evidence of iliac arterial calcification had a lower 1-year survival after transplant than those who did not (92% vs 98%, respectively; p = 0.05).”

    Application of a Novel CT-Based Iliac Artery Calcification Scoring System for Predicting Renal Transplant Outcomes 
Davis B et al.
AJR 2016; 206:436–441
  • “Excellent interobserver agreement was noted for each calcification score category. The common iliac arteries showed significantly higher average calcification scores than the external iliac arteries for all categories. Advanced age and diabetes mellitus were independently predictive of higher scores in each category, whereas hypertension, cigarette smoking, hyperlipidemia, and sex were not. Based on multivariate analysis, only the calcification morphology score of the arterial segment used for anastomosis was independently predictive of a higher rate of surgical complexity and of DGF. None of the scores was predictive of graft or patient survival. However, patients with CT evidence of iliac arterial calcification had a lower 1-year survival after transplant than those who did not (92% vs 98%, respectively; p = 0.05).”


    Application of a Novel CT-Based Iliac Artery Calcification Scoring System for Predicting Renal Transplant Outcomes 
Davis B et al.
AJR 2016; 206:436–441
  • “Excellent interobserver agreement was noted for each calcification score category. The common iliac arteries showed significantly higher average calcification scores than the external iliac arteries for all categories. Advanced age and diabetes mellitus were independently predictive of higher scores in each category, whereas hypertension, cigarette smoking, hyperlipidemia, and sex were not. Based on multivariate analysis, only the calcification morphology score of the arterial segment used for anastomosis was independently predictive of a higher rate of surgical complexity and of DGF. None of the scores was predictive of graft or patient survival.”

    Application of a Novel CT-Based Iliac Artery Calcification Scoring System for Predicting Renal Transplant Outcomes 
Davis B et al.
AJR 2016; 206:436–441
  • Abdominal Aortic Aneurysm: Facts
    • AAA is generally defined as a 50% or more in- crease in anteroposterior (AP) diameter of the aorta (diaphragm to iliac bifurcation), generally 3 cm or greater in the average adult.
    • More than 85% of AAA are infrarenal (>1 cm below the lowest renal artery), most being diagnosed before the threshold for intervention (5–5.5 cm)
    • Less commonly, an AAA can be juxtarenal (involving the renal arteries or with 1 cm of them) or suprarenal  (involving the aorta and visceral branches above the renal arteries). More cephalad aneurysm extension is associated with a more complex repair.
  • Abdominal Aortic Aneurysm: Rupture
    The main differential encountered in practice is whether or not an AAA is ruptured. Rupture is most frequently into the retroperitoneum along the posterolateral wall. Disrupted intimal calcium, frank aortic wall discontinuity, and extravasated IV contrast are all specific signs of rupture. Additional CT signs for rupture include the crescent sign and the drape sign. The crescent sign is a high-attenuation (higher than psoas muscle) crescent-shaped abnormality that is associated with the aneurysm mural thrombus/aortic wall. The drape sign occurs when the posterior aortic wall lacks a sharp margin and distinct fat plane with the adjacent vertebral body (drapes over it).
  • Endovascular Abdominal Aortic Aneurysm Repairs: Complications
    Endoleaks
    Device migration
    Device fractures
    Aneurysm growth
  • “Over an 8-year period, 988 patients underwent EVAR, of whom 42 (4.3%) required secondary interventions involving placement of additional endovascular devices.”
Endovascular stent-graft repair of failed endovascular abdominal aortic aneurysm repair.


    Baril DT et al.
Ann Vasc Surg. 2008 Jan;22(1):30-6.
  • “The mean time from initial operation until second operation was 34.1 months. Failures included type I endoleaks in 38 patients (90.5%), type III endoleaks in two patients (4.8%), and enlarging aneurysms without definite endoleaks in two patients (4.8%).”
Endovascular stent-graft repair of failed endovascular abdominal aortic aneurysm repair.


    Baril DT et al.
Ann Vasc Surg. 2008 Jan;22(1):30-6.
  • “Abdominal aortic aneurysm is defined as a pathologic dilatation of the abdominal aorta to more than 3 cm in the greatest diameter. Abdominal aortic aneurysm remains a leading cause of death in the United States, with at least 45,000 operations and 4500 deaths from rupture in the United States each year.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “Approximately 90% of all abdominal aortic aneurysms are infrarenal. Fusiform abdominal aneurysms are most common (accounting for 80% of cases) and arise in a setting of atherosclerotic degeneration. Saccular aneurysms are less common, are more spherical with a narrower neck, and may arise secondary to a penetrating ulcer or have an inflammatory or infectious origin.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “Surgical thresholds for aneurysm repair vary depending on the location of the aneurysm, but most vascular surgeons electively repair typical fusiform abdominal aortic aneurysms that exceed 5.4 cm in the greatest diameter. The median abdominal aortic aneurysm expansion rate is 3.2 mm per year, with growth rate correlating with aneurysm size according to the Laplace law. Most abdominal aortic aneurysms grow 1–4 mm per year, and rupture risk versus operative risk is balanced at a 5.0–5.5-cm threshold for intervention. Surgical repair is indicated for aneurysms that enlarge more than 5–7 mm within 6 months or 1 cm or more within 1 year. In some cases, rapid enlargement or a strong family history of rupture may indicate early repair.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • Preoperative CT Signs of Aneurysm Instability 
    - the hyperattenuating crescent sign 
    - wall irregularity 
    - periaortic hematoma
    a new saccular outpouching
    the draped aorta sign 
  • “The hyperattenuating crescent sign refers to a periluminal curvilinear area of hyperattenuation within the wall or thrombus of the aorta. At unenhanced CT, the crescent has higher attenuation than the intraluminal blood. When intravenous contrast material is used, the crescent has higher attenuation than the psoas muscle . Histopathologically, this finding results from infiltration of blood from the aortic lumen into the surrounding mural thrombus and/or wall, which severely compromises and weakens the wall.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “Mehard et al reported that the hyperattenuating crescent sign is strongly associated with other signs of aortic instability, as well as frank rupture, and has a specificity of 93%. It is essential that crescentic intramural hemorrhage not be confused with homogeneous circumferential mural thrombus or diffusely hypoattenuating mural thrombus, which frequently coexist with abdominal aortic aneurysm.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “The presence of periaortic hematoma adjacent to an abdominal aortic aneurysm reflects loss of integrity of the aneurysm wall and is a high risk factor for frank rupture. At CT, periaortic hematoma appears as a focal area of soft-tissue attenuation arising from or intimately associated with the aorta. The hematoma is most commonly posterolateral but may be circumferential. Perianeurysmal fat stranding may be present and can extend beyond the immediate periaortic region.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “It should be noted that patchy, discontinuous intimal calcification is commonly found in both stable and unstable aneurysms. However, focal discontinuity of otherwise circumferential calcified intimal plaque and outward displacement of calcified intimal plaque may indicate a contained rupture at unenhanced CT and definitely indicate a contained rupture if they are new findings. Evaluation of MPRs helps confirm the saccular appearance of the disrupted wall.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “The draped aorta sign, another indication of contained rupture, refers to the posterior aortic wall closely following or “draping” along the contour of the adjacent vertebral body. The aorta may appear indistinct from the vertebral body or psoas muscle, with loss of periaortic fat planes. Again, the multiplanar reconstruction correlate shows a saccular outpouching indicative of focal breach of the aneurysm wall in the region that appears draped on axial images."

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “Penetrating atherosclerotic ulcer (PAU) is a complication of aortic atherosclerosis that renders the wall unstable, with a risk for ulcer expansion, saccular aneurysm formation, and aortic rupture. Defined as an atherosclerotic ulcer that extends through the intima and into the media, it predominantly occurs in the thoracic aorta but can also affect the abdominal aorta. The abdominal aorta was involved in 30% of patients in one series of 388 subjects.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “The rate of surgical graft polyester degradation is reported to be 31.4% at 10 years and 100% at 25–39 years . As a result, there is a greater risk for graft failure with increasing time from graft placement. Anastomotic pseudoaneurysm formation (ie, a contained rupture) occurs in 0.2%–15% of surgical grafts . In patients with long-standing surgically repaired aneurysms, grafts should be inspected for changes in appearance over time that indicate instability as opposed to expected fusiform dilatation.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “Aneurysms should be thoroughly inspected for CT indicators of instability, including plaque lysis, the hyperattenuating crescent sign, periaortic hematoma, new saccular outpoutching or focal displacement of calcified intimal plaque, and the draped aorta sign. After endovascular or open aneurysm repair, refractory endoleaks, graft weakening, and anastomotic pseudoaneurysms can also signify a risk for rupture. Because CT is the primary modality for serial aneurysm imaging and is frequently used to evaluate abdominal pain in the emergency setting, radiologists must be familiar with the CT indicators of aneurysm instability to expedite surgical management and potentially avert aneurysm rupture.”

    Abdominal aortic aneurysms revisited: MDCT with multiplanar reconstructions for identifying indicators of instability in the pre- and postoperative patient.

    Wadgaonkar AD, Black JH 3rd, Weihe EK, Zimmerman SL, Fishman EK, Johnson PT.
    Radiographics. 2015 Jan-Feb;35(1):254-68
  • “AAA represents a progressive increase in the aortic luminal diameter and is the 10th most common cause of death in the Western world. AAA is usually described by its relationship to renal arteries (i.e., suprarenal or infrarenal). The normal diameter of the suprarenal abdominal aorta is up to 3.0 cm, and that of the infrarenal abdominal aorta is 2.0 cm. Aneurysmal dilation of the infrarenal aorta is defined as a diameter ≥3.0 cm or dilation of the aorta ≥1.5 times the normal diameter; on the basis of these criteria, 9% of people aged >65 years have an AAA.”
     
    Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings
     
    Khosa F et al
    J Am Coll Radiol. 2013 Oct;10(10):789-94
  • “Emergency surgery for aortic aneurysm rupture is associated with 46% mortality (as opposed to 4%-6% for elective repair), and rupture occurs with increasing frequency as the aneurysm size exceeds 5 cm. It is therefore valuable to detect AAAs and follow up until elective repair is indicated.”
    Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings
    Khosa F et al
    J Am Coll Radiol. 2013 Oct;10(10):789-94

  • When do you follow-up aneurysms for interval change?

    Aortic Diameter (cm) Imaging Interval

    2.5-2.9                                   5 y

    3.0-3.4                                   3 y

    3.5-3.9                                   2 y

    4.0-4.4                                   1 y

    4.5-4.9                                   6 mo.

    5.0-5.5                                   3-6 mo.

  • “Aneurysms involve common and internal iliac arteries more commonly than external iliac arteries. Iliac artery aneurysm is defined as a vessel diameter ≥1.5 times the normal iliac artery diameter or ≥2.5 cm in diameter. Iliac artery aneurysms are rare in isolation; Lawrence et al reported a prevalence of 6.58 per 100,000 hospitalized men and 0.26 per 100,000 hospitalized women in the United States. Aneurysms that are <3.0 cm in diameter tend to be asymptomatic, rarely rupture, and expand slowly; those that are 3.0 to 3.5 cm should be followed up with cross-sectional imaging initially at about 6 months. If stable, repeat scanning can be performed annually. Iliac artery aneurysms >3.5 cm have a greater tendency to rupture and should be followed more closely or treated expeditiously.”
    Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings
    Khosa F et al
    J Am Coll Radiol. 2013 Oct;10(10):789-94

  • “Aneurysms involve common and internal iliac arteries more commonly than external iliac arteries. Iliac artery aneurysm is defined as a vessel diameter ≥1.5 times the normal iliac artery diameter or ≥2.5 cm in diameter. Iliac artery aneurysms are rare in isolation; Lawrence et al reported a prevalence of 6.58 per 100,000 hospitalized men and 0.26 per 100,000 hospitalized women in the United States. Aneurysms that are <3.0 cm in diameter tend to be asymptomatic, rarely rupture, and expand slowly; those that are 3.0 to 3.5 cm should be followed up with cross-sectional imaging initially at about 6 months. If stable, repeat scanning can be performed annually.”

    Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings
    Khosa F et al
    J Am Coll Radiol. 2013 Oct;10(10):789-94

  • “Splenic artery aneurysms are the most common visceral aneurysms and the third most common intra-abdominal aneurysm, after those occurring in the aorta and iliac arteries . In a series of >300 visceral artery aneurysms, 70.9% were of the splenic artery. The vast majority are true aneurysms, although pseudoaneurysms related to prior inflammation, especially pancreatitis, or infection may occur. The estimates of prevalence of splenic artery aneurysms vary, but a retrospective review of nonselective angiograms suggests that an incidence estimate of 0.8% may be the most accurate .”

    Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings
    Khosa F et al
    J Am Coll Radiol. 2013 Oct;10(10):789-94

  • “Risk factors for developing these aneurysms are similar to those for other aneurysms. In a review of the clinical features of 217 patients with splenic artery aneurysms, hypertension was present in 50.2%, obesity in 27.6%, coronary artery disease in 23.5%, and hypercholesterolemia in 21.7%. Splenic artery aneurysms occur more frequently in women .”

    Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings
    Khosa F et al
    J Am Coll Radiol. 2013 Oct;10(10):789-94

  • “ Accurate detection of complications in AAAs is crucial to perform prompt therapeutic interventions, and CT angiography is of vital importance for monitoring the size of the aneurysm as well as differentiation of the potential complications of AAAs.”
    Multidetector computed tomography findings of abdominal aortic aneurysm and its complications: a pictorial review
    Taheri MS et al.
    Emerg Radiol (2013) 20;443-451
  • CT of Aortic Aneurysms: Impending Rupture
    - Anuerysms risk of rupture will vary with size. Per year risk is quoted as;
    - < 4cm less than 1% per year
    - 4-5 cm is 1-3% per year
    - 5-7 cm is 6-11% per year
    - 7 cm or greater is up to 20% per year
  • CT of Aortic Aneurysms: Impending Rupture
    - Hyperattenuating crescent sign
    - Decreased thrombus to patent lumen ratio caused by increase in diameter
    - Extravasation of contrast media into the mural thrombus of AAA
  • CT of Aortic Aneurysms: Complications
    - Aorto-caval fistula
    - Aorto-left renal vein fistula
    - Aorto-enteric fistula
    - Infected AAA
  • Genetic Syndromes: Repair
    - Aortic root or ascending aorta > 5 cm OR rate of enlargement > 0.5 cm per year
    - For those who need aortic valve replacement, root or ascending aorta repair if > 4.5 cm
    - Smaller patients have lower thresholds
    - Counsel patients considering pregnancy at size of 4.0 to 4.5 cm
    - LDS patients – repair at 4.5 cm
  • Abdominal Aortic Aneurysm
    - Defined as aorta larger than 3 cm
    - 4 - 5.4 cm can be monitored
    - Fusiform > 5.4 cm warrants repair
  • Abdominal Aortic Aneurysm
    - Aortic aneurysm rupture 77-94% mortality
    - Risk factors for AAA rupture ~
    - female gender
    - larger baseline AAA diameter
    - hypertension
    - continued tobacco use
    - cardiac or renal transplant
  • Impending AAA Rupture
    - Clinical diagnosis difficult
    - CT indicators of aneurysm instability
    - Rapid increase in size
    - Lumen: plaque ulceration 
    - Wall: intramural hemorrhage (crescent)
    - Periaortic: retroperitoneal or intraperitoneal hemorrhage
    - Guide timely surgical management
  • Aneurysm Growth Rate
    - Most grow 1-4 mm/year
    - Growth rate correlates with size
    - Aneurysms that enlarge rapidly are at higher risk for rupture
    - Surgery indicated for rapidly enlarging aneurysms
  • Instability: Crescent Sign
    - Infiltration of blood from the aortic lumen into mural thrombus and/or wall
    - Periluminal curvilinear hyperdensity in aortic wall 
    - Higher attenuation than the lumen on unenhanced CT
    - Severely weakens the wall
  • Contained AAA Rupture
    - Aorta wall no longer fully intact, but hemorrhage  is enclosed
    - thrombus 
    - retroperitoneal soft tissues
    - Focal outpouching of previously
        intact aortic wall reflects
        contained rupture.
  • Draped Aorta
    - Contained rupture
    - Posterior wall of aorta “drapes” along the contour of the adjacent vertebral body
    - Aorta indistinct from adjacent structures with loss of periaortic fat planes
    - vertebral body
    - psoas muscle
  • “Aortic aneurysm rupture, aortic dissection, PAU, acute aortic occlusion, traumatic aortic injury, and aortic fistula represent acute abdominal aortic conditions. Because of its speed and proximity to the emergency department, helical CT is the imaging test of choice for these conditions. MR imaging also plays an important role in the imaging of aortic dissection and PAU, particularly when the patient is unable to receive intravenous contrast material. In this era of MDCT, conventional angiography is used as a secondary diagnostic tool to clarify equivocal findings on cross-sectional imaging.”
    CT of acute abdominal aortic disorders
    Bhalla S et al.
    Radiol Clin North Am 2003 Nov;41(6):1153-69
  • “Acute aortic occlusion is a rare but catastrophic pathology resulting from thrombus formation, saddle embolism, false-lumen expansion in aortic dissection, aortic trauma, and other etiologies related to arteriosclerosis or hypercoagulability. Postoperative mortality is extremely high even if blood perfusion to the lower
    extremities is restored by emergent surgical intervention.”
    Acute Occlusion of the Abdominal Aorta with Concomitant Internal Iliac Artery Occlusion
    Yamamoto H et al.
    Annals of Thor and Cardiovasc Surg 17(4), 422-427, 2011-08-01
  • “Studies have shown that the causes of death were attributed to a wide range of pathologies including respiratory failure (eg, respiratory distress syndrome), mesenteric ischemia, fatal arrhythmia, myocardial infarction, stroke, hyperkalemia, or renal failure, and most of the patients who died after revascularization appear to have had fatal organ failure even without obvious arterial occlusion in major organs.”
    Acute Occlusion of the Abdominal Aorta with Concomitant Internal Iliac Artery Occlusion
    Yamamoto H et al.
    Annals of Thor and Cardiovasc Surg 17(4), 422-427, 2011-08-01
  • “Prognosis of acute aortic occlusion is considerably poor. Postoperative mortality has been reported to be between 14% and 60% in the studies analyzing 10 or more patients with acute aortic occlusion.”
    Acute Occlusion of the Abdominal Aorta with Concomitant Internal Iliac Artery Occlusion
    Yamamoto H et al.
    Annals of Thor and Cardiovasc Surg 17(4), 422-427, 2011-08-01
  • “ Aortoiliac CTA provides relevant information on aortic root and iliofemoral vessel anatomy for preinterventional planning. CTA reveals clinically significant incidental findings in a high number of patients considered for transcutaneous aortic valve implantation, which may have a significant impact on patient selection.”
    Aortoiliac CT Angiography for Planning Transcutaneous Aortic Valve Implantation: Aortic Root Anatomy and Fequency of Clinically Significant Incidental Findings
    Apfaltrer P et al.
    AJR 2012; 198:939-945
  • “ Almost half the patients (101/207) had clinically significant incidental findings, including noncalcified pulmonary nodules larger than 8 mm (n=7), pulmonary embolism (n=3), or aortic aneurysm (n=12).”
    Aortoiliac CT Angiography for Planning Transcutaneous Aortic Valve Implantation: Aortic Root Anatomy and Fequency of Clinically Significant Incidental Findings
    Apfaltrer P et al.
    AJR 2012; 198:939-945
  • Aortoenteric Fistulas: CT Findings
    - Fistulae between native aorta and the adjacent bowel
    - Hematoma may seen in the periaortic aorta
    - Penetrating ulcer of the aorta is seen
    - 80% of the fistulae involve the duodenum
  • Aortoenteric Fistulas: Clinical Findings
    Gastrointestinal bleeding
    80%
    Sepsis
    44%
    Abdominal pain
    30%
    Back pain
    15%
    Groin mass
    12%
    Abdominal pulsatile mass
    6%
  • Aortoenteric Fistulas: Facts
    - Without surgical intervention mortality approaches 100%
    - Primary fistula are rare and most cases are secondary and a result of aortic reconstructive surgery
    - Secondary fistulae may occur between 2 weeks and 10 years post surgery
  • "Although the CT features of aortoenteric fistula and perigraft infection often are similar, ectopic gas, loss of fat plane, extravasation of aortic contrast material into the enteric lumen, and leakage of enteric contrast material into the paraprosthetic space are highly suggestive of aortoenteric fistula in a patient with gastrointestinal bleeding."

    Aortoenteric Fistulas: CT Features and Potential Mimics
    Vu QDM et al.
    RadioGraphics 2009; 29: 197-209

  • Aortoenteric Fistulas: Differential Dx
    - Retroperitoneal fibrosis
    - Infected aortic aneurysm
    - Infectious aortitis
    - Perigraft infection without fistulization
  • "However the overall combined utilization rate of both types of AAA treatment has remained stable in the Medicare population. There is no evidence to suggest that the introduction of the newer approach has led to overteatment of patients."

    Endovascular Repair vs Open Surgical Repair of Abdominal Aortic Aneurysms: Comparitive Utilization Trends from 2001-2006
    Levin DC et al.
    J Am Coll Radiol 2009;6:506-509

  • "Treatment for AAA seems to be an example of the responsible use of new technology by physicians. The newer, less invasive and less risky procedure is replacing the older and more invasive procedure to a considerable degree."

    Endovascular Repair vs Open Surgical Repair of Abdominal Aortic Aneurysms: Comparitive Utilization Trends from 2001-2006
    Levin DC et al.
    J Am Coll Radiol 2009;6:506-509

  • Abdominal Aortic Aneurysms: Facts
    - Intervention indicated when size is = 5.5 cm
    - Short term outcome improved with endovascular stents but long term is not significantly different than open repair
  • "Aortic body paragangliomas are accompanied by other synchronous paragangliomas in about 10% of cases."

    Cross-Sectional Imaging of Paragangliomas of the Aortic Body and Other Thoracic Branchiomeric Paraganglia
    Balcombe J et al.
    AJR 2007; 188:1054-1058
  • "Loeys-Dietz Syndrome manifests with aggressive vascular pathology. Aneurysms may form at a young age and have a propensity for arterial dissection. In addition, aneurysms rupture at diameters smaller than those used to dictate surgical intervention for other syndromes and disorders".

    Loeys-Dietz Syndrome: MDCT Angiography Findings Johnson PT, Chen JK, Loeys BL, Dietz HC, Fishman EK AJR 2007;189; 226
  • "The combination of arterial enhanced phase and unenhanced imaging performed at 1-month follow-up offers improved specificity and positive predictive values compared with arterial phase images alone. Delayed phase imaging does not significantly increase sensitivity for detection of endoleaks, but it does depict low flow endoleaks not seen on arterial enhanced phase."

    Iezzi R et al. Radiology 2006;241:915-921.
  • "The combination of arterial enhanced phase and unenhanced imaging performed at 1-month follow-up offers improved specificity and positive predictive values compared with arterial phase images alone."

    Multidetector CT in Abdominal Aortic Aneurysm Treated with Endovascular Repair: Are Unenhanced and Delayed Phase Enhanced Images Effective for Endoleak Detection
    Iezzi R et al.
    Radiology 2006;241:915-921.
  • "The combination of arterial enhanced phase and unenhanced imaging performed at 1-month follow-up offers improved specificity and positive predictive values compared with arterial phase images alone. Delayed phase imaging does not significantly increase sensitivity for detection of endoleaks, but it does depict low flow endoleaks not seen on arterial enhanced phase"

    Multidetector CT in Abdominal Aortic Aneurysm Treated with Endovascular Repair: Are Unenhanced and Delayed Phase Enhanced Images Effective for Endoleak Detection?
    Iezzi R et al.
    Radiology 2006;241:915-921.
  • "Delayed phase imaging does not significantly increase sensitivity for detection of endoleaks, but it does depict low flow endoleaks not seen on arterial enhanced phase."

    Multidetector CT in Abdominal Aortic Aneurysm Treated with Endovascular Repair: Are Unenhanced and Delayed Phase Enhanced Images Effective for Endoleak Detection? Iezzi R et al. Radiology 2006;241:915-921.
  • "Study results indicate that arterial phase imaging may not be necessary for the routine detection of endoleaks. Radiation exposure can be decreased by eliminating this phase."

    Abdominal Aortic Aneurysm:Can the Arterial Phase at CT Evaluation after Endovascular Repair Be Eliminated to Reduce Radiation Dose?
    Macari M et al.
    Radiology 2006; 241:908-914.
  • CTA for Endoleaks: What Phase(s) of Acquisition are Needed?

    - Unenhanced phase
    - Arterial phase
    - Delayed phase
  • "MDCT angiography is a reliable method for evaluating the aortoiliac and lower extremity arteries."

    MDCT Compared with DSA for Assessment of Lower Extremity Arterial Occlusive Disease: Importance of Reviewing Cross-Sectional Images
    Ota H et al.
    AJR 2004; 182:201-209
  • Pseudoaneurysms: Etiology

    - Trauma
    - Iatrogenic
    - Infection
  • Abdominal Angina: Facts
    - Female > male by 3-1
    - Mean age is 60 years
    - 18% of patients over age 65 have mesenteric arterial stenosis but few are symptomatic
    - Caused by stenosis or occlusion of the celiac, SMA or IMA
    - At least 2 of the vessels and often all 3 are involved
    - Occurs 15-60 minutes after meals
  • What is abdominal angina?

    Definition: abdominal angina is also known as chronic mesenteric ischemia, and is a syndrome of chronic arterial insufficiency of the intestine. Clinical symptoms are increased epigastric pain which typically occurs with increased demand for splanchnic blood flow after a meal.
  • "Multidetector row CT angiography with appropriate postprocessing techniques is highly effective for the diagnosis, evaluation, and treatment of suspected abdominal angina."

    Multidetector Row CT Angiography in Patients with Abdominal Angina Cademartiri F et al. RadioGraphics 2004; 24:969-984
  • "In patients with an acute abdomen, the coronal images may clarify confusing anatomy, add confidence to interpretation, and provide a perspective familiar to referring surgeons."

    MDCT of Patients with Acute Abdominal Pain:A New Perspective Using Coronal Reformations from Submillimeter Isotrophic Voxels Paulson EK et al. AJR 2004;183:899-906
  • In patients with acute abdominal pain, MDCT with coronal reformations from submillimeter isotrophic voxels provides a useful adjunct to axial images."

    MDCT of Patients with Acute Abdominal Pain:A New Perspective Using Coronal Reformations from Submillimeter Isotrophic Voxels Paulson EK et al. AJR 2004;183:899-906
© 1999-2017 Elliot K. Fishman, MD, FACR. All rights reserved.