Abdominal Aortic Aneurysm Rupture: Radiologic Findings

Contents Under Pressure: Radiologic Findings of

Abdominal Aortic Aneurysmal Rupture

Zev WienerHarvard Medical School Year III

Gillian Lieberman, MD

Zev WienerGillian Lieberman, MD

Our Patient: Initial Presentation

• History of Present Illness:63 year-old woman with a known history of abdominal aortic aneurysm (AAA) presents with acute onset chest and lower back pain s/p MVC

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Our Patient: Initial Presentation

• Past Medical History: Hypercholesterolemia, PUD, s/p gastric bypass

• Family History: AAA in father and uncle• Vitals: Hypotensive in the 80’s• Labs: WNL

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Differential DiagnosisGI• Appendicitis• Small bowel obstruction• Large bowel obstruction• Gastritis / PUD• Diverticular disease• Pancreatitis• Ischemic bowel• Reflux

GU• Pyelonephritis• Nephrolithiasis

Cardiovascular• AAA• Aortic Dissection• MI

Miscellaneous• Musculoskeletal pain

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Differential: Potential PitfallsIn particular, ruptured AAA is often

misdiagnosed as:

-Renal colic-Diverticulitis-MI-MSK back pain

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Our Patient: DiagnosisGiven patient’s history, a complication of

AAA is very high on the differential

What is an AAA?

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Abdominal Aortic Aneurysm (AAA)

Dilatation of the abdominal aorta to > 1.5 times its normal diameter

Normal diameter is approx. 2 cm

An AAA is therefore defined as an aortic diameter greater than 3 cm

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http://www.health‐news‐blog.com/blogs/permalinks/4‐2008/will‐screening‐for‐aortic‐aneurysm‐be‐effective.html


Anatomy of the Aorta

95% of AAA’s are infrarenal

About 2/3 extend into one or both of the iliac arteries as well

8http://www.dartmouth.edu/~humananatomy/figures/chapter_30/30-1.HTM


AAA: Risk FactorsOdds Ratio

• Smoking 5.57• Male sex 4.56• Positive family history 1.95• White versus black race 2• Atherosclerosis 1.5• Hypertension 1.2• (Diabetes) (0.54)

9Aneurysm Detection and Management (ADAM) Veterans Affairs Cooperative Study Group, Ann Inter Med 3/97


AAA Rupture: Risk Factors

• Aneurysm diameter• Rate of expansion• Female gender• Other less proven factors

-Smoking-Decreased FEV1-Amino terminal procollagen propeptide

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Risk of Rupture: Diameter

Diameter (cm) Annual Risk (%)< 4.0 04.0-4.9 0.5-55.0-5.9 3-156.0-6.9 10-207.0-7.9 20-40>8.0 30-50

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J Vasc Surg 2003 May;37(5):1106-17


Risk of Rupture: Rate of Increase

• 0.19 cm per year for aneurysms 2.8 to 3.9 cm in baseline diameter

• 0.27 cm per year for those 4.0 to 4.5 cm in baseline diameter

• 0.35 cm per year for those 4.6 to 8.5 cm in baseline diameter

• Rate of increase is more rapid in smokers (Estimates of 20-25% increase in rate)

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Risk of Rupture: Gender

Risk of rupture in women is significantly higher than in men

May reflect smaller initial lumenal diameter


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Risk of Rupture: Other Factors

• Diameter is not the whole story…

-10 - 24% of ruptured AAAs were less than 5 cm in diameter (Nicholls, et al)

-Some have advocated looking at geometry of aneurysm (contribution to wall stress) as opposed to mere diameter (Vorp, et al)

-Other factors include ongoing smoking, decreased FEV1, diabetes mellitus, and serum marker amino-terminal procollagen propeptide


AAA: Importance of Early Detection

• When repaired electively, mortality is 0.9- 5%

• When repaired after rupture, mortality is up to 75%

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Alexander S, Bosch JL, Hendriks

JM, Visser

JJ, Van Sambeek

MR.

The 30‐day mortality of ruptured abdominal aortic aneurysms:

influence of gender, age, diameter and comorbidities.

J Cardiovasc

Surg

(Torino).

Oct

2008;49(5):633‐7


Clinical Presentation of AAAPre-Rupture

-Usually asymptomatic

-Vague epigastric discomfort

-Mild back/abdominal pain

Post-Rupture

-Severe, constant pain in abdomen or back.

-Tachycardia / Hypotension

-Pulsatile abdominal mass

-Nausea and vomiting

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Menu of TestsPre-Rupture• Plain film• Ultrasound (US)• Computed Tomography

(CT)• Magnetic Resonance

Angiography (MRA)• Digital Subtraction

Angiography (DSA)

Post-Rupture*• CT• US

*If not diagnosed clinically

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The E.D. opted for C.T.

Our Patient

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Diagnosis of Rupture: CTPRO’S

-Detailed imaging of aneurysmal size, location, and neighboring anatomy

-Delineates presence of thrombus

-Detect active extravasation

-Reveals systemic effects of rupture 19


2020

CON’S

-TIMEAvg. time to diagnosis on CT = 83 minutes (compared to 5.4 minutes of ultrasound) (Plummer D, et al: Abstract at 1998 SAEM, Chicago, IL.)

-Contrast (allergy/ renal function)-Expensive


Our patient’s CT findings…

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Out Patient: Aortic Arch

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PACS, BIDMC

Axial (C+) CT


Jagged, irregular aortic arch

Our Patient: Aorta

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Free fluid

Calcified aorta

PACS, BIDMC

Axial (C+) CT


Our Patient: High Attenuating Crescent Sign

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Possible intramural hematoma

PACS BIDMCAxial (C+) CT

Companion Patient: High Attenuating Crescent Sign

http://www.radiologyassistant.nl/en/452fe3aa7ef9c

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http://rsna2005.rsna.org/rsna2005/V2005/conference/event_display.cfm ?id=66601&em_id=4415819

Represent an acute hematoma within either the mural thrombus or the aneurysmal wall, strongly associated with AAA rupture (75% PPV)

* *

Our Patient: Hematoma

Retroperitoneal hematoma

Extravasated contrast

PACS, BIDMC

Axial (C+) CT 26


Our Patient: Site of Rupture

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Site of rupture

PACS, BIDMC

Axial (C+) CT

Widest diameter (post-rupture) = 4.7 cm


Most Common Site of Rupture

• Right lateral wall - 28% • Pelvic arteries - 22% • Posterior wall - 19% • Left lateral wall - 17% • Anterior wall - 10% • Suprarenal - 4%

Radiology.

Jun

2007;243(3):641‐55.

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Our Patient: Site of Aneurysm

Renal artery

PACS, BIDMC

Coronal (C+) CT29


Infrarenal AAA’s95% of AAA’s are infrarenal

About 2/3 extend into one or both of the iliac arteries as well

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Our Patient: Aneurysm Shape

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Possible fusiform morphology (post- rupture)

PACS, BIDMC

Coronal (C+) CT


Shape of Aneurysm

Saccular AAA’s are thought to be more prone to rupture than fusiform AAA’s.

-CT “tortuosity index” may provide a more accurate prediction of rupture

Annals of Vasc. Surgery, 22:1 88-9732


http://neuro.wehealny.org/endo/images/11_01.jpg

Systemic Effects of Aneurysmal Rupture in our Patient

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Our Patient: Flattening of IVC

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“Slit-like” IVC

PACS, BIDMC

Axial (C+) CT


Our Patient: Renal Displacement

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Anteriorly displaced R kidney

PACS, BIDMC

Axial (C+) CT


Site of Hemorrhage• Retroperitoneal - 85.3%• Peritoneal - 7.1% • Inferior vena cava (IVC) or iliac vein -

5.8% • Enteric - 1.8%

J Vasc Surg. Jan 8 2009

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Retroperitoneum: Anatomy

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http://radiographics.rsna.org/content/28/6/1571/F2.large.jpg

Our Patient: Kidneys

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Wedge shaped segment of hypoenhancement

PACS, BIDMC

Axial (C+) CT


AAA: Renal Involvement

As many as 30% of patients with AAA have concomitant renal artery stenosis

Iezzi R, Cotroneo AR, Filippone A, Di Fabio F, Santoro M, Storto ML. MDCT angiography in abdominal aortic aneurysm treated with endovascular repair: diagnostic impact of slice thickness on detection of endoleaks. AJR Am J Roentgenol. Dec 2007;189(6):1414-20.

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Our Patient: Liver

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PACS, BIDMC

Axial (C+) CT


Wedge shaped area of hypoperfusion

Other Possible CT Findings That Were Not Evident in Our

Patient

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AAA Rupture: Periaortic Stranding

http://www.ajronline.org/content/vol188/issue1/images/large/01_05_1554_03C.jpeg42


Focal Calcium Discontinuity


47% PPV43


Tangential Calcium


74% PPV 44


Draped Aorta

61% PPV


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Are there any other options for evaluation of a ruptured AAA?

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Screening: Ultrasound• Excellent screening tool prior to rupture

– Simple and safe– Cost-effective– No exposure to ionizing radiation– Sensitivity and specificity nearly 100%– However, highly operator dependent

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http://www.med- ed.virginia.edu/courses/ rad/edus/index8.html

Diagnosis of Rupture: Ultrasound- Not as reliable as CT, but may be the only

viable diagnostic option for the hemodynamically unstable patient

- Use of contrast enhanced US aids detection

- One report cited a 4% sensitivity in US detection of rupture

- When combined with other clinical factors, however, sensitivity was 95%

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AJR 2005; 184:423-427


Diagnosis of Rupture: Baseline Ultrasound

http://www.ajronline.org/content/vol184/issue2/images/large/00_03_0181_01a.jpeg 49


Diagnosis of Rupture: Contrast Enhanced Ultrasound

http://www.ajronline.org/content/vol184/issue2/images/large/00_03_0181_01b.jpeg 50


Diagnosis of Rupture: Contrast Enhanced Ultrasound

http://www.ajronline.org/content/vol184/issue2/images/large/00_03_0181_02anew.jpeg51


Diagnosis of Rupture: Color-Flow Doppler Ultrasound

- Color-flow Doppler can aid in detecting the site of extravasation

- Adjustment to low velocity scales may be necessary to register leaks with low flow rates

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http://www.vmth.ucdavis.edu/cardio/cases/case38/color_flow.htm

CT vs USAverage time to diagnosis by bedside US =

5.4 minutes

Average time to diagnosis by CT = 83 minutes

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Plummer D, et al: Abstract at 1998 SAEM, Chicago, IL.

Our Patient: Treatment

Patient underwent emergent open repair of AAA with placement of a 12 mm Dacron graft

https://clevelandclinic.org/heartcenter/pub/guide/disease/aorta_marfan/marfansurgery_act ual.htm

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Treatment of Ruptured AAA

May be repaired open or endovascularly

http://www.gvg.org.uk/aaagraft.jpgBritish Journal of Radiology (2005) 78, 62-64

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Our Patient: 4 Month Follow Up

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Normal sized Lumen

KidneyPACS, BIDMC

Axial (C+) CT


Our Patient: 4 Month Follow Up

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PACS, BIDMC

Axial (C+) CT


Thickened bowel wall

Potential Postoperative Complications

• Colonic ischemia (1st week)• Aortoenteric fistula• Atheroembolism• Declamping hypotension• Acute renal failure• Impotence (sympathetic plexus injury)• Anterior spinal syndrome• Graft infection 58


Summary

- Ruptured AAA can be diagnosed clinically, with CT, or with US

- While CT can provide exquisite detail regarding the rupture and systemic effects, the necessary time sacrifice is a considerable drawback

- Ultrasound is a rapid diagnostic modality, but is highly operator dependent and not as informative

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Acknowledgements

Rich Rana, MDGillian Lieberman, MDPrachi Dubey, MDGraham Frankel

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References• Alexander, S. "The 30-day Mortality of Ruptured Abdominal Aortic Aneurysms: Influence of Gender, Age, Diameter and

Comorbidities." Journal of Cardiovascular Surgery (Torino) 49.5 (2008): 633-7. • Brewster, D. C. "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 37.5 (2003): 1106- 17.

• Catalano, O. "Contrast-Enhanced Sonography for Diagnosis of Ruptured Abdominal Aortic Aneurysm." AJR Am J Roentgenol 184 (2005): 423-7.

• Iezzi, R. "Contrast-enhanced Ultrasound versus Color Duplex Ultrasound Imaging in the Follow-up of Patients after Endovascular Abdominal Aortic Aneurysm Repair." Journal of Vascular Surgery (2009).

• Iezzi, R. "MDCT Angiography in Abdominal Aortic Aneurysm Treated with Endovascular Repair: Diagnostic Impact of Slice Thickness on Detection of Endoleaks." AJR Am J Roentgenol 189.6 (2007): 1414-20.

• Morales, J. P. "Endovascular Repair of a Ruptured Abdominal Aortic Aneurysm under Local Anaesthesia." British Journal of Radiology 78 (2005): 62-4.

• Nicholls, S. C. "Rupture in Small Abdominal Aortic Aneurysms." Journal of Vascular Surgery 28.5 (1998): 884-8. • Norman, P. E. "Abdominal Aortic Aneurysm: the Prognosis in Women Is Worse than in Men." Circulation 115 (2007): 2865. • Pappu, S. "Beyond Fusiform and Saccular: A Novel Quantitative Tortuosity Index May Help Classify Aneurysm Shape and

Predict Aneurysm Rupture Potential." Annals of Vascular Surgery 22.1 (2008): 88-97. • Stavropoulos, S. W. "Imaging Techniques for Detection and Management of Endoleaks after Endovascular Aortic Aneurysm

Repair." Radiology 243.3 (2007): 641-55.

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Abdominal Aortic Aneurysm Rupture: Radiologic Findings